Air To Air Vs Air To Water Heat Pumps: What's Better?

Adam talks us through the differences between air to water and air to air #heatpumps, and tells us about his experience with both!
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[@richardc1983]

Hey Adam, love your channel and this is one that needs to be done however the system you describe at 1:58 is a multi split system. A mini split is a 1-1 system e.g wall mount and 1 outdoor. I think more research needs to be done by yourselves on the type of air to air indoor units available. I have ducted units installed upstairs in my loft (1930s terrace) I have 2 units that do the bedrooms and another unit that does the landing and bathroom... No return air in the bathroom. It looks neat and cooling all over in the summer. The downstairs has ducted units in bulkheads with a front grill and lower return air grill so there is no ductwork but the units are hidden. This looks similar to a hotel room and looks decent. I do however use my combi boiler to provide hot water still. Of course you can go for the cheap wall mounted units (that you wrongly call cassette units) or a cassette unit (that you have in your studio in the ceiling) or console units that go where a radiator would go that have an air outlet that opens in heating to direct warm air at your feet. I do agree though, radiant heat is spot on and is the nicest comfort for heating. However it's the balance... I prefer the cooling in summer so that works for me really well. Rads are also generally under windows so generally a more comfortable room ensues. The air to water systems available now can either be used with rads, a mixture of rads and fan coils or just fan coils. So you could have rads for the bathrooms for that radiant heat effect and then fan coils for the rooms you want cooling. That way you are getting the best. Go for a system such as lg therma v with heat recovery and when the system is in cooling in summer the heat that would normally be rejected to outside can be used to heat the hot water. Your unit in your studio sounds like it's been cycling on and off which generally means it's over sized for the space... Running in low fan speed reduces the kw output. You can also in the wired controller settings set the ceiling height which basically reduces the fan speed steps. E.g max fan speed on high might actually be medium fan speed when you set high ceiling mode. Set the ceiling mode to a low ceiling height which means the unit will move air slower and therefore less KW output (compressor will reduce it's output to match) you will also see less temp fluctuations. Make sure the airflow vanes are set to the lowest so it pushes the airflow to the floor. You can also set the thermostat on and off range to say 0.5c, and set it to read from the wired controller which is at the height of room occupation.. so change it over to read from that... As otherwise you won't get accurate readings at the warm toasty ceiling level due to stratification. Happy to tell you how to make these changes. Most a/c engineers won't understand the control side of it. Commercially though having dealt with both I still prefer separate chillers for the cooling water and boilers (or other heat source to provide the heating water) for the fan coils. This setup is more configurable and has more fine tuning available. Fan coils however are an excellent way to provide heating and cooling and you can really maximise your heating and cooling efficiencies by using weather compensation controls for both the chilled water and heating water flow temps. I think you've jumped the gun based on experience with the performance of your office unit which I think is unfair. So many variables and field settings that could be configured to improve its performance. Happy to help if asked.

[@Etacovda63]

Yes, he’s got too much opinion wrapped up in one (as you said, oversized sounding) install. It’d be like me comparing air to water by looking at a cowboys air to water install.

[@alexlovett1991]

To be fair I’m pretty sure ceiling units are called cassettes. (I’ve been looking into these very recently)

[@richardc1983]

@@alexlovett1991 I've a cassette unit in my summer house/office at home as didn't want wall space take up it works great.

[@CamTracey]

When you say fan coils, you mean like the unit on the wall in a split system? I wish I could find the same support/information/access to good reliable heating technicians here in Austria the same as you guys in the UK

[@richardc1983]

@@CamTracey yep fan coil = indoor unit. Any unit that has a fan and a coil to do the heating or cooling.

[@mfdsuk]

Some other benifits to consider. Having the heat transfer device higher on the wall gives more freedom on furnature arrangement and limits the ability for humans to block the heat source by for example putting a sofa in front of the radiator. Air to Air is also able to dehumidify the air, dry air is easier to heat or cool then wet air and much more comfortable in the summer. Air to air is also much quicker to respond, meaning with a smart home setup in the future, using presence detectors, you could accurately heat only the rooms that are being used, you can do this with water but it's much slower to respond to changes.

[@davidbolt8256]

In Western Australia we commonly have ducted A2A heating and cooling in our homes. The system is quite simple, unit outside, unit in the roof space , ducting manifold for zoning and insulated ducting to every room. All the ducts are zoned so you can turn on/off each room. Cop avg 3.5 on our 13 year old inverter Daiken system (cooling slightly better than heating). In use it heats the house from cold to 23 degrees C in 15mins and cools to same temp nicely up to 42 degrees C (regularly 36-40 degrees C in summer). A simple system with little to go wrong. Sound is not an issue, neither the temp fluctuations in my experience. Dry skin points etc all agree and domestic hot water heating requires additional system.

[@JohnJKelly-of4dc]

Thats what im interested in to be honest.

[@gav7507]

The talk about the cassettes being ugly is interesting because as you say in Western Australia (where I also live) but also North America it's very common to install a ducted system where all you can see is literally a small square in the roof or wall that air comes out of, it's no more visible than a LED light for gods sake. Without question it's more aesthetically pleasing than a radiator that you can actually see and trip over or bang into not to mention it needs to be maintained and can leak. Why so many people have a 100+ year old heating system in the UK and try to jerry rig new technology into it is beyond me, it costs a fortune. In Western Australia an entire (very large) home can be cooled or heated for around 5000gbp with a entire-house ducted system which you can't even notice existing or a small mini split can be installed for 600 gbp which admittedly is a box on the wall but it does not look that bad.

[@fredrikhjelmare2266]

Interesting to hear you're heating 'from cool' to cost warm inside. Is cool some -10-20 degrees Celsius or more +15 Celsius? 😅

[@jeltesikkema8364]

No matter how you look at this, a2a deserves a place in the energy transition. Those A++ models on scop are highly efficient. If underfloor heating is not possible these A2A are hard to beat on scop

[@johnzach2057]

They can also dehumidify. Which is very important for tightly insulated buildings.

[@Boz1211111]

For humidity just open window. It can only cool to dehumidify, its not a dehumidifier

[@johnzach2057]

@@Boz1211111 All AC units can dehumidify. The dehumidifiers we use are mini AC units. The principle is the same. Pass air through a cold surface and water vapor will condense into liquid water and trickle down to the exit. This is why every AC unit has a drain hose installed and if it gets clogged it the internal AC unit leaks water. And for the winter most AC have the dry function which makes them work primarily as dehumidifiers and keep cooling the room to a minimum

[@ChrisBrown-xf2ce]

@@johnzach2057 the dehumidified air while A2A is heating is created in the heart pump outside while it picks up the latent heat outside & moves it to the cassette inside. In short, there's no dehumidifying effect in the property when heating, only when cooling

[@rcjhaynes]

I’ve got UFH on ground floor. Putting UFH on 1st floor and loft. In readiness for a2w HP. But still have issue of bedrooms on the back west facing and loft on particular (insulated with multi foil) overheating in summer. I’m thinking maybe multi room a2a. Looking forward to pcm insulation that heats and aid’s cooling by absorbing heat.

[@gsum1000]

I'll be very interested in your findings when you do your comparison. We installed a single mini-split in our living room in April so don't have sufficient experience as yet but the results so far are very encouraging. Installation took a total of 5 hours at a cost of just over £2000. On the day of installation, the air temperature was 6C and the 35 m^2 living room temperature had fallen to 14C. The unit raised the temperature to 21C in about 20 minutes, after which it went into what I call 'wafting mode' in which warm air is wafted silently and without noticeable draughts into the room. Periodically, the unit goes into heating mode but only for a few minutes. In heating mode the sound of the unit is pleasant white noise and is inaudible in wafting mode. The system uses 800 W to produce 3.5 kW of heat when in heating mode and uses maybe 50 to 100 W when in wafting mode, effectively giving a sky-high CoP. On the first day of operation the system used 2.1 kWh for eight hours of operation to heat just the living room. Open the double doors and the system is able to heat the ground floor of our house when the air temperature is 6C. It's early days for us but currently we're leaning towards adding a second mini-split on the other side of the house plus one of those water tanks with a heat pump on top although we're still considering going the 'wet' route. Indications are that 7 kW will be sufficient heating for our ground floor - we don't like heated bedrooms.

[@averyvaliant]

Cost wise, is it possible to work out a rough estimate as to how much it's costing you to heat your room or ground floor each day, or month?

[@HeatGeek]

The system will not always use 800 for 3 5 output. Ide say that was at mild outdoor temps

[@richardc1983]

@@HeatGeek the inverters will ramp down depending on both outdoor temp and indoor conditions... So yes even at 5c outside if the indoor temp is .5c off the set point then it will ramp right down.

[@matthewhunty]

Why was it so expensive

[@markcross5572]

Graham, your scenario is exactly the same as mine. I have gone from storage heaters to a 4.5kw mini split taking me from 14000kwh a year to 10000kwh saving me about £1000 a year. Just ordered a hot water tank with heat pump on top to replace my immersion heater and await its arrival.

[@petanders1968]

Hi Adam We installed 3 air 2 air daikin units last year, lounge, and 2 bedrms, we are gradually decommissioning our boiler and radiators and are just keeping the immersion heater for hot water. After a yrs operation we are pleased with both the cooling and heating of our bungalow, which we control with remote or smartphone app, we can control the direction of air,it's very quiet when operating, has a bacterial filter which cleans the air! and our energy bill, so far, is around £50 - 70 pmth, bear in mind we are very energy conscious and try not to use too much hot water, the wim hof showering method was a little bit uncomfortable in the beginning but now cold showers are the norm all yr round! Peter

[@kevfquinn]

On "what do you do for hot water" - hot water is a tiny proportion of my gas use - something like 5%. Heating is 95% of my usage - so I'm not concerned about hot water costs (if it came to it, that'd be about choosing the right sized hot water tank to avoid heating water I won't use, or maybe a sunamp thermal battery instead of a water tank). One reason for considering air-to-air instead of air-to-water, is getting rid of the radiators everywhere and getting the walls back.

[@HeatGeek]

The average is more like 25% rather than 5%

[@johnhunter4181]

Most poeple considering A2A or A2W already have a gas boiler so why not keep that for DHW and add A2A with no disruption and a fraction of the cost of A2W? When it comes to DHW heat pumps are nowhere near as efficient and often have addtional immersion heaters for legionella anyway. This way you have a backup if either system breaks down. Forget the £7.5k BUS grant - it only inflates the install cost of A2W.

[@HeatGeek]

@@johnhunter4181 because they are efficient on DHW. Your thinking on this is outdated, it’s did used to be the case a few years back though. My hot water is 4.7 scop for example. Research the heat geek super culinder

[@sorepaws]

Thank you for the time and effort in promoting newer technologies for heating and the challenges in meeting a greener environment. Probably covered already, however I think there is some confusion about "radiant heat" and what a water heating "radiator" does. For the most part a normal household "radiator" is actually a form of convection heating, it heats all the air in the room, a small amount of heat can be detected through "radiant heat" but only if you are standing close to it. Second point of confusion about the boundary layer of air around the body and insulation, the reality is that heat is removed by evaporation of moisture from the skin, but increasing the dew point and including a fan there can be an increase in cooling effect. It does seem that from most channels there is only one solution for heating, heat pump or boiler. Why don't you consider the benefit of mixed systems, i.e. Gas boiler (combi) for basic heat and hot water, air to air heat pump for heat boost and cooling. This is probably especially a better solution for properties with insufficient sized radiators and pipe work for a heat pump installation. We are unlikely to escape the need for Natural Gas for a decade or 2 especially given the only predicable source of electricity is from Gas powered stations, at least a gas boiler is >90% efficient and nearly twice as efficient as the conversion from Gas to Electricity offered by the most efficient power stations. So what does that mean? Well in part the true environmental efficiency of an Air to Water heating system is actually closer to 2:1 rather than the user getting 4:1

[@HeatGeek]

Just to correct your error. An a2a is 0% radiant heat (least comfort), a wet system is 80% convection and 20% at 70c flow temp design, and a low temp steady state design 30% convection -70% radiant

[@sorepaws]

@@HeatGeek I don't think I mentioned that A2A was anything other than hot air convection, while I agree a wet system is more comfortable for heating, there is a benefit of considering a combination of Wet and A2A system for heating/cooling, we get more days over 30C ( I know you have tried cooling radiators, but as I recall condensation was an issue) . Summer '22 saw temperatures over 39C - with A2A you can keep the place cool. I have underfloor heating which while being very efficient has the negative of slow thermal inertia - an A2A system supporting the wet system enables a room to be heated quickly and cheaply. While I am not an HVAC engineer I consider that an holistic approach to environmental management is important. This is just my experience in a reasonably insulated (40cm loft insulation - recent cavity wall insulation) house originally built in the 1980's

[@protectiongeek]

Seriously considering A2A for our house (28yo 3-bed semi). Based on performance of a Daikin A2A ASHP we have operated for 3 years in our garden office (floor area 15 sqm) I estimate a SCoP of 4 to 4.5. Works no problem in our location (West Central Scotland). Main considerations are cooling (expecting longer and longer hot spells in summer) and no radiators (don't underestimate the flexiblilty that affords). Comfort IS an issue. Wall mounted cassettes have to be carefully placed to avoid sitting in direct airflow but our existing Daikin can vector the output airflow to avoid this. For DHW considering just direct immersion heater (only used twice a day for one hour so about 6kWh max) until we can afford PV + battery etc. Thanks for a great video!

[@russellwelch4193]

What’s the model of your A2A. Would love a positive recommendation. Looking at mini splits upstairs.

[@protectiongeek]

@@russellwelch4193 it’s a Daikin model RXP50M2V1B (outdoor ASHP unit) with model FTXP50M2V1B indoor wall-mounted cassette. To be honest, we didn’t choose that specific unit. We ordered the “air-con” option from the builder of the pod and their subcontractor decided on the spec’. Having watched a lot of Adam’s Heat Geek vids and gained a little more knowledge (I’m a retired power utility engineer) I would say the unit is probably significantly oversized for the expected heat loss. That said A2A doesn’t enjoy the same thermal inertia of A2W (for the specific heat capacity reasons explained by Adam in this vid) so having a more powerful unit allows fairly rapid heating or cooling when it’s needed and then settles down to keeping the environment just how you like it. If we do go ahead and put A2A in the house, I’d probably consider mainstream manufacturers such as Mitsubishi etc.

[@benhart777]

Daikin are the kings of heat pumps. If you stick with then you can’t go wrong. Indoor units like the Daikin Emura have all the features you need, & will avoid any of the problems mentioned in this under-researched video

[@bassplaya69er]

@@protectiongeek daikin are one of the top dogs in Asia BTW for mini splits at least.

[@richardc1983]

@@russellwelch4193 look at LG units that's what I have in my own home... Really good system.

[@dus10dnd]

There are water heaters (boilers) that use air-to-air, built in. EDIT: I would add that the variability of temperature is likely based on the specific units you have used. Some work in a way to continuously operate at a very low power draw only mildly modulating the temperature until the difference increases enough to warrant a full operational mode.

[@chrisolsen4578]

In norway we mostly use air to air. It helps to distribute the cold air from the floor and blend it with hot air in the ceiling.

[@HeatGeek]

With radiant heating there is little issue woth stratification.

[@HeatGeek]

@Vicki a basic search on Google will show you how radiant heating doesn't stratification in a room

[@krunchie2024]

We have A2A minisplit, they're very common in Japan as coolers, but are being increasingly used as heaters, even in the coldest parts of the country. Ours is 7.2kW and heats around 50sq m x 2 floors. 20C on the ground floor gets enough heat up the stairs to give us 17C in the bedrooms upstairs. We are 800m above sea level and Jan and Feb average -3C. Coldest nights are -15 to -17C. The heat pump is a Mitsi designed for cold regions. We had underfloor and a woodstove in another house, but don't miss them at all.

[@johnhunter4181]

Adam admits that air-to-air isn't really Heat Geek's thing - fair enough - but having read through all the comments it's clear everyone with experience of A2A loves it. One big argument for a wet system is that you'll need it to heat your hot water tank but hot water isn't that expensive with an electric immersion, especially if you take into consideration maintenance and installation costs. In fact for us it isn't much more than the standing charge for gas. The boiler upgrade scheme doesn't apply to A2A but the £5k grant just seems to go into the installers Christmas fund anyway.

[@HeatGeek]

I don’t think everyone that has it loves it at all!!! I had it and HATED it. I have a close friend that’s an air con engineer and had just removed his for a wet system

[@johnhunter4181]

​@@HeatGeek I commented 10 months ago and guess what, we now have a new gas boiler as well as A2A. For a week in Feb we tried heating with the boiler but it was more expensive than the 2x3.5kW mini-splits. Our house is well insulated, so we've never had a warm glow off the radiators and comfort-wise I can't feel any difference. The best thing about going the A2A route is that there''s no disruption to the existing CH system which we now use for just DHW and towel rails (10mins in the morning) all the other rads are off but still an option if you come and stay with us or electric prices go through the roof. What is even more comforting than warm radiators is having choices and backup systems for heating and DHW ...and cooling!

[@HeatGeek]

@@johnhunter4181 your comparing intermittent heating with a2a. That’s not what I was talking about. Steady state wet heating is the competitor and it’s wayyy more comfortable

[@johnhunter4181]

@@HeatGeek I don't get what you mean. A2A or A2W they are both heat pumps and as intermittent or steady state as you want. We just set the room temp and leave it to maintain that. Our so called 3.5kW units can output up to 6.00kW with input power modulating between 240W ~ 1.26kW. I'm wondering if your experience is with houses that need a lot of heating because I can see that would make a big difference. For example in an easily heated house with gas central heating the radiators may never feel warm - always below body temperature or with A2A it would require a only gentle barely warm breeze from the a/c. Whereas a colder leaky house that needs a lot of heating, will have radiators giving a lovey warm glow wheras an A2A system would be blowing a hot air in your face. I guess the same applies if you're turning off the heating during the day and trying to heat the house quickly after coming home from work.

[@HeatGeek]

@@johnhunter4181 it’s not to do with the blowing, it’s to do with the radiant effect. The comfort of the radiant effect comes from you not loosing radiant heat out rather than radiant heat coming in to you… if you google you can find some niche articles and research.. it’s an article I’ve had half finished for about 8 years now and I’d love to get to it one day!

[@benhart777]

Okay, Air to air heat pumps from the big Japanese companies; Daikin & Mitsubishi, and to a lesser extent Toshiba, Panasonic etc: they’ve been making air to air heat pumps that both heat and air condition for decades; they have unparalleled levels of experience, and 91% of households in Japan have a heat pump (higher than the percentage of American households with AC) of for both heating and air conditioning; bear in mind houses in Japan are generally extremely draughty and cold in the winter, but they use individual spilt units to warm the room they’re in, then switch it off like the lights when they move to another room… also, if the US, the greatest country in history are happy with a forced air heating system (they generally use a furnace for heating & an external heat pump for cooling, with the condenser in the same ductwork as the furnace - still, it’s providing heat via air, and they are quite happy with it.) There’s a feature called VRF: Variable Refrigerant Flow (Daikin; the original inventor of this technology use their proprietary name VRV or Variable Refrigerant Volume)… What this does is allow the compressor to run at different speeds, so instead of having a system like our British central heating which is either full blast, or off (which was and IS STILL also the way with many air conditioners / heat pump systems… So you have a much more consistent temperature, which is more comfortable, and more efficient… Air to air heat pumps have come a long way. Modern indoor units from the top Japanese brands have features such as, aiming the air flow away from people in the room, and uses the Coanda effect and distributes air more evenly to avoid draughts… also, they have “whisper quiet” operation; as low as 19db which is virtually inaudible… They have other features that I can’t think of off the top of my head. For a new build, with high performance glazing and insulation, an airtight building envelope, an air to air system is a must; albeit in combination with a mechanical ventilation heat recovery system for distributing clean filtered air; the units will provide more than enough heating, and the air conditioning will be increasingly needed - the climate in Tokyo or other parts of Japan is actually rather similar to the UK. I don’t quite understand why people in the UK don’t have it. I was in Belgrade, Serbia recently, and the old brutalist Yugoslav socialist housing blocks in New Belgrade (or Novi Beograd) are covered in mini split outdoor units, and Belgrade doesn’t really get much hotter than here (unless it’s at the business end of one of our bombs we dropped in ‘99)… Belgrade can certain gets COLDER than the UK. Many new air to air heat pumps is heat recovery to provide the capability to both cool and provide hot water at the same time, and some even are capable of heating in one room while cooling in another, by cooling the room wanting cooling, then using that heat removed from that room to warm the next room. Air to air systems have come a long long way. Your bog-standard commercial AC unit will not provide the best experience; you should really look at some more recent, residential units, because they are excellent and relatively affordable. Also, air conditioning does dehumidify the air. This is especially important in new builds in the UK which often have problems with damp, because they are heavily insulated but totally un-breathable. They would benefit most from an air to air heat pump for the efficient heating, cooling and dehumidification. If you’re skin feels dry, you can always get a humidifier, but generally in air con mode, a heat pump system will maintain a relative humidity of around 50% which is perfect. You can even hide a concealed unit in ductwork in the ceiling.

[@richardc1983]

Hey fella. Vrf or vrv as it's also known depending on whether mitsi or Daikin, what you describe is an inverter driven compressor that first came out on those systems. Now standard on even the most basic split units. It's amazing how technology has moved on. There is even now wind free units that use a fine mesh over the air outlet so you don't feel air movement as it uses such a slow induction of air into the room. LG multi split units have a feature called smart load control that also came from vrv/vrf where the refrigerant condensing tempersture is allowed to fluctuate depending on the temperature and humidity. If it's mild outside the air off inside will be pleasant as gentle cooling is needed if it's 40c outside then the air off will be colder to allow for increased cooling capacity. The new units even sense humidity to ensure the unit can remove humidity on a very humid day whereas on a typical warm mild day when humidity is low then mild cooling is needed.

[@tomkacandes8286]

@Ben Hart You make many good points about many things in your post. VRV/VRF is not “a feature”, it is a significantly different application than split units typically using “branch boxes” that redistribute and VARY the flow of refrigerant to downstream emitters. Each outside condenser can serve one or more branch boxes that then serve many emitters. Heat recovery has to be designed into the pipe work system and can (but might not, depending on the design) allow emitters to exchange Btus so one room is cooled while another is heated using the removed Btus.

[@benhart777]

@@richardc1983 thanks for the reply. Technology really has moved on so much, it’s incredible. I’ll check out some LG systems. I admit I’m a bit biased towards Japanese companies, particularly Daikin & Mitsubishi, they’ve been pioneers in heat pump technology for decades, but in reality I’m sure LG & even the German Bosch are just as good these days, with their own technologies (German companies are a bit notorious for commercial espionage so they have probably reverse engineered all the Japanese units lol). There are some good American heat pump / AC manufacturers like Carrier, but I’m not sure if they’re available in the UK. Thanks for your insight, I appreciate your reply 👍

[@benhart777]

@@tomkacandes8286 thanks for the reply. I appreciate your input. I’m not an expert, but I know enough to have been annoyed by this video lol. Regarding heat recovery, do you need an extra piece of equipment, or is it just a matter of installing the system (obviously one that’s compatible with heat recovery) in a certain way (I know there are 3 pipe systems, & some even manage to do it with 2 pipes)… Also, the kind of air to air heat pumps available from Daikin or whoever; can they at least heat a hot water tank, or would I need a separate system for that - a tankless water heater or something, or a separate heat pump? Or is it possible to install the common air to air units with at least the ability to heat a hot water tank. Thanks again for your knowledge and your reply. 👍

[@richardc1983]

@@benhart777 mitsi are still one of the good ones but daikin seem to have issues these days poor products an and after support. Mitsi also take ages to come back to you. LG seem to be very good as do the Samsung wind free units. To get heat recovery the mini vrf branded units as they will be able to simultaneously heat and cool diff rooms at a time but hot water facility you would need to check they do not water like Daikin therma v which says it's heat recovery. all modern units with an inverter vary the compressor speed and refrigerant volume by using an EEV, electronic expansion valve.

[@begicj]

Hi Adam, I installed a heat pump 9kw with an digital inverter that has both air to water and air to air that can work in tandem two years ago. I have an underfloor heating and a 200l domestic hot water tank which is connected to a hidrobox. From my own experience I use air to air for cooling (I don't need to cool floors) and for heating only when I need to quickly heat a room like in periods in early autumn when I need to heat my house only for a few hours in the evening because underfloor heating is very slow.

[@HeatGeek]

Hi Josip. What was the cost?

[@begicj]

@@HeatGeekoutdoor unit 9kw, hidrobox 9kw, indoor wall unit 5.7kw, valves, tank 200l and pipes without instalation was around 5000£

[@jakeii9]

What's the manufacturer/model that can do air to air and water? Sounds awesome!

[@redwhite_040]

Which country do you live? (climate) And do you have floor insulation?

[@AllElectricLiving]

Get a Infra red heater to test I would love to see the differences in all the technology’s

[@velianlodestone1249]

Whole house air systems are a whole different beast though - typically in a US house you will find mini splits (which is what you are talking about) to be fairly rare, they provide extra oomph ("Party heaters") but in general the whole house air system takes care - they typically have very sluggish airflow (like 24CFM). But those mini-splits have unbeatable efficiency - they're prolific in our office buildings which is a testament to their function

[@Nevermind301]

I can't see why you would be getting more radiant heat from low temp emitters. Quite the opposite in fact, heat from radiation is a function of T^4, so a even a slight increase in DT would increase the heat produced exponentialy. I would guess that high temp emitters would have more radiant heat compared to natural convection.

[@kevinhill1851]

Hey there. Firstly, just wanted to express my appreciation for all your content - it provides a backbone for lots of the research I do on the heating side of sustainability, in our quest to get our rather awkward house better for the planet. We have been trying to make progress on solar for quite a long time now, and finally have a company helping us out, but I was very interested in your brise soleil. I went hunting for UK suppliers of this, but found nothing particularly useful. Did you that feature get installed by a company specialising in that kind of thing? Do you have any kind of details surround that that might help me research that further? Thanks for any help you can give. K.

[@MrGraeme]

I'm In Scotland. For my situation, if I was to move to Heat pumps I would find it easy to have multiple units on the same shared external wall [house is long and slim]. I have Microbore pipe running through my home's 15 year + old heating system (New gas boiler was put in last winter as it was cheap). Believe it or not it's the cooling function I want. If I spend more money [and get a wet system only] I lock myself out of the cooling feature from ATA. I already run a portable AC unit which is super inefficient but it's the only way to cool the place down one the hotter summers [which even in Scotland are becoming more frequent]. Even if I was to add the Heat pump with the gas boiler and keep it [for the time being] I'd still be better off.

[@davetaylor4741]

Very well thought out and presented. Gives a lot of food for further thought. I have lived in Qld Australia for the last 24 years. Air to air heatpumps as you are calling them are everywhere and so I have lots of experience of them. The system you have in your building I would say is old fashioned and pants. Newer ducted systems are way more efficient. Computer controlled and fully zoned. An app on your phone can micro control and even turn them on and off remotely. And yes they are very good at cooling which in Qld is the biggest thing. Heating. As you say biggest concern in UK. They work but as you say are they cost effective. I don't know. We only heat for a few weeks not months. Hot water. We use a lot of solar hot water being the Sunshine state. Our Aircon is powered by the Sun. The UK is getting hotter and you freak over 30C but not yet up with Qld. The newer Aircon systems have multiple outlets in a room for better distribution and are pretty quiet. That is on a new build where you can install the ducting. Retro fits usually just have a head unit. Not so good. The crux would be the heating aspect. Even if a water heat pump was cheaper I personally still wouldn't install one as they are now. Constantly on. Often little control over temperature. And ridiculously expensive. As UK gets hotter and cooling becomes more important. Aircon might win the day. All the cars are getting it now. That wasn't the case before I left.

[@xorsyst1]

Thanks for this video. We looked at an A2W system, but we had installation issues. Basically the A2W system used a mono unit so the hot water is generated outside, but logistics meant that it would require burying that hot water pipe along the side of the house for about 10 meters to get to the right part of the house to take water - which was a big expense given the ground is textured concrete. An A2A system would just have the ducted lines running outside along the wall, much simpler. In both cases though, we have a hot water issue - we have no tank at all at the moment, just a combi. And no obvious place to put a tank either. We haven't come up with a solution for that (other than a gas water heater, which kinda defeats the point given standing charges).

[@highlanderes]

Our A2A floor unit Daikin heats up our main room with 2 and a half walls of floor to ceiling windows very well without cold floors. The 4th wall is all kitchen, so no place for a radiator. We do have a hot water tank direct to electricity. It is not that noisy if you pick the right one, and some radiators are quite noisy too.

[@HeatGeek]

How is a radiator noisy?

[@highlanderes]

@@HeatGeek In three of the places with radiators I have lived, they had their distinct noises. Clonk sounds when pipes move in their mounts in the wall due to temperature changes. Water traveling through bent pipes and valves at high pressure can make noise. Gravel or rust getting swirled around in one radiator or continuously through the system.

[@peterswinson326]

mini split systems have advanced a lot with beezeless and low noise fans (Midea systems are excellent at this) the main issue not mentioned is that they don't heat the air evenly in the room as there is no convected heat, so if you have the fan on low and are working in the room sitting down, your feet can be cold and your head warm, we had to use a normal oil filled radiator to fix this, I have looked at funneling some air to the bottom of the room when heating, but not easy to do, I tried blowing the cold air up at the intake with a fan but this had little effect as well, great video as always

[@darrenr1995]

We agree, we install Midea, the breezeless cassettes and wall units are great. No noise either.

[@richardc1983]

Get a ceiling fan and run it in reverse this gently stirs the air up in the room to avoid stratification. I do this myself.

[@peterswinson326]

@@richardc1983 that would be great but we have a low ceilings in the rooms with aircon and I'm quite tall :)

[@Tim_Small]

If you were going "too hot then too cold" all the time then was the unit oversized and cycling a lot (or perhaps a poor spec one with little or no modulation - so that it was running flat out, or not at all)? With Air-to-Air you can have the similar problem with undersized indoor units as you do with wet systems which have undersized radiators - if the indoor units are undersized, then you need high air temperatures or high fan speeds to get enough heat into the room.

[@richardc1983]

So many variables and so many field settings that could be tinkered with in the wired remote... Unit deffo short cycling of it was fluctuating so much.

[@matthewhunty]

Air to air heat pumps work on pressure. Never put one in the toilet area. In a Small flat put one in the community areas. Cut off he bottom of the doors and allow the heat to go through the rooms that way. If nobody goes into the rooms they are heated but not fully. I have been using them quite a lot in small flats. The units were costing about £600 so I was fitting two separate units. I installed the 2.5 kW units on their own at Spurs. An electrician providing the PowerPoint Also the final bit of the install was done by a F gas engineer. The install is very easy if you buy small units rather than one big one with multiple headers. The biggest advantage is the Aircon. You can run it for a minute and it will dehumidify the air. So if your tenant decides to do the washing in the flat they can remove the moisture.

[@FarObserver]

Aircon all the way baby! Just had a Daikin multisplit installed. No sweaty balls for me this summer 😎😎

[@glightsolutions]

HOT WATER A2A info. The Daikin Multi + units offers indoor cassette units and Hot Water cylinder 90 or 120L via multi split. Great for conversions, granny flats, home office. Haven’t installed one yet. EKHWET-BV3. Hope that helps some people. Straight heat pump and wet system would be my preference but A2A have their place

[@nickjenkey]

Last year we installed an air to air unit in our workshop (Mitsubishi, 6.8kW nominal heating output). Experience with the unit over a winter and a summer has been good. The setback function and air circulation is great in a workshop where things need to be kept damp free. Another pro for a building that is not always occupied is fast response, and a nice woosh of warm air to thaw hads after being in the yard. The biggest downside is definitely noise, in the workshop it doesn't matter but I would not want the noise of the fan in my house, even though it's not particularly loud. The cassette/indoor unit is quite big too and I agree on the visuals. The treat this summer to have air-conditioning on a few days was great and knowing it was powered entirely by PV was nice. So like you said in the video, a good technology for some places but for domestic properties maybe less good. Cost wise the unit has saved a fortune compared to running the kerosene heater that was there before, plus no smell or lighting to do. To keep the damp off it uses about 4-5 kWh a day.

[@keithoneill6273]

I find the noise from my Midea 3.5 kw single outlet in my living room is minimal, as it the noise from the outdoor unit. I'm very please with it. I still have my gas CH system, but it is hardly ever used.

[@dontuno]

We have a mini split system and I would say none of what you experienced in your office applies to us. Whisper quiet, and I really do mean whisper! It's more than capable of a rapid ramp and maintaining a set point temperature. For the initial outlay I am more than happy with its performance and I will seriously be considering a further unit next year and especially given it is a very easy install.

[@tanasescuvalentin812]

There are monobloc heatpumps foar heating water here in europe for about 600 euro 100liters but it cools the air in the room, if you want with piping to drag the air from outside and blow outside that is about 800 euro, also it can cool for free during the summer when in heats water. For a2a there are indoor units mounted like a radiator under the window, there are sistems that control humidity. All calculated still much cheaper than a2w. Here in Romania a2a unit with mounting costs 500 euro inverter wifi etc. heating water 1000 so 5 rooms = 2500 euro+ hot water 1000 euro = 3500 euro. If you wand under window internal that is more expensive, double the price so total about 7000 euro.

[@Pyramid333]

Air to air is the best solution for the UK homes. The problem is that the companies keep people away from technology. With air to air you do not use water, maintenance, and gas which is classed as dangerous. In my experience also the people who are called experts for boilers are totally profit drivers and they have little knowledge. Air to air is used in countries where the winters are -15 degrees and they work totally fine. There they are called inverters. UK middlemen promote old technology for heating so they can make money. Why do install heat pump with water tank which is very outdated technology and do not work, plus spend so much. 2 bedroom home can use 12kw air to air and have 3-4 internal units and the cost is very low, maybe 2-3k max. Just to let you know air to air installation in other countries is 100£ here in the UK they will slam you with labour cost that is ripping off.

[@robertwestinghouse4098]

Good points....What about throwing in Infra Red Heating??

[@edc1569]

Think most of us have moved on from 1920s technologies.

[@robertwestinghouse4098]

@@edc1569 Thank you for the reply. Local people are heralding IR as the new best thing since sliced bread. So it is not good and more expensive??

[@alexlovett1991]

Very interested in this. Just moved into a Victorian house from a 80s house with an air to water system. We’re planning on air to water for underfloor downstairs, and air to air upstairs as the air con in the summer we feel is going to be a must alongside the dehumidification. I guess the other thing we like about the mini splits is freeing up wall space (it’s mounted high up so furnitures can go against walls). The difference in temps upstairs in our house is also quite big some rooms have 1 external wall with others having 2-3, sure could balance rads but it feels like the individual zoning might work nicely.

[@jackplant9232]

I have recently bought a house that was originally built in 1735 and am planning on doing something very similar, I am also planning on using an electric shower and under sink water heaters as my hot water usage will be quite low and I think the reduction in efficiency will be offset by the gain in efficiency of running the downstairs heat pump at a lower temperature

[@alexlovett1991]

@@jackplant9232 I’d steer clear of electric shower tbh. A heat pump will be so much cheaper to run, and a much better shower. When we upgraded the showers were so much better

[@jeltesikkema8364]

Nice! But one thing that puzzles me: can you feel radiant heat from an object that is lower in temperature then your body? Like from those low temp radiators that operate at let's say 35 degrees?

[@HeatGeek]

Not specifically. But it means your body radiates less heat out to those object and the other objects in the toom and keeps more heat in

[@martingibbs1179]

The human body isn't that good a temperature detector as its all about relative heat. The body is constantly touching "air" so typically anything hotter than room temp will feel warm and anything less than room temp will feel colder. Its my experience that hot water pipes carrying water greater than 25 C will feel warm but not hot and those less than 25 C will feel cool to the touch.

[@Tim_Small]

Yeah you can - you feel it as less heat loss. The opposite of this is when you are standing a couple of meters from a cold single-glazed window in winter - the air temperature might be 19C, but you still "feel a chill" from it, and this goes away when you pull curtains across the window - some people call it "coolth" (as the opposite of warmth).

[@mikediamond3697]

Hi, by the sounds of things the ceiling cassette in your office is not the best around especially for a domestic environment but that is very much neither here nor there. I work in energy management and have to do total life analysis on a large number of different space heating solutions including both A2A and A2W heat pumps. In a domestic setting A2A has a huge advantage, especially if being used across the property and that is level of control, every unit becomes its own zone and if the unit is off then there is no consumption as opposed to a wet system were water is still being circulated through the room (consuming energy) and losing heat from the pipework (which is generally not lagged) to areas that are not in use and that's assuming that the homeowner has isolated the radiator in the unused room which generally isn't the case, especially if the room is being used sporadically throughout the day. I would generally recommended A2A systems for bedrooms because of this and because of the cooling options. Another pro is if you have PV, especially a smaller array then heating can be very much targeted to where you need it at a consumption that is reasonable for a small array on a brightish winter day. There is obviously a lot more to it and I do not fall on one side or the other of that argument highlighted by the fact that I have both systems in my home.

[@brackcycle9056]

Norway & Sweden A2A heat pumps are very popular . You can get a stand alone "Hot water tank with a heat pump built in " , popular in the USA less than £2k . But A/c systems that rev up in the night or create draughts are not to my taste . Once installed A2W monobloc can be upgraded to next gen Monobloc as very simple job. A2A will nearly be a new install each time. But the big question " A2A to A2W , which one will be the Betamax ?"

[@MyShyCats]

I have Fujitsu A2A ductless mini split -very very quiet. SEER is 19-21.5 for cooling. The HSPF(?) for heating is 9-10.3

[@AL-lz1hb]

Daikin have a three way split plus the holy grail of hot water! Currently in Europe but arrivng in Britain soonish? Who knows? Be good if the govt would fund air to air but taking off the vat is a good start. No idea what price yet. Some folks with no rads would prefer not to have them due to furniture issues. Fitting heating is expensive but having to buy new stuff too is crazy. What do folks think of the sunamp thermino as a fit and forget water solution?

[@Richardincancale]

I installed a multi split Daikin A2A in my apartment in Paris. It was a more expensive system than some competitors but both the indoor and outdoor units were close to silent once they’re in temperature maintain mode, after initial warm up for ten minutes. Key for me was the silence and the pleasure of being cool in summer in a south facing flat with large windows, as well as warm in winter. I didn’t have dry skin, or suffer from noise (and I’m very noise sensitive). I heated water with a combi gas boiler but had plans to change to an A2W for Hot water. Now I’ve moved to a house with oil CH so the natural move here is a large A2W system.

[@yscol1313]

With your new A2W system, will the level of cooling from the system be sufficient in summer? Will you have to attach fans to the radiators?

[@Richardincancale]

@@yscol1313 Fair point, in Paris it was often 30+ degrees, occasionally 40 degrees and the cooling was the first reason to get a heat pump. But I’ve moved away and summer temperatures here are usually 10 degrees cooler due to the proximity of the sea, so I didn’t miss cooling even in this record breaking summer.

[@yscol1313]

@@Richardincancale Thanks for the info - so I assume if cooling is a big deal for someone, a2a is still the way to go over a2w?

[@Kangenpower7]

Richard, with a oil heater system, I would suggest a 18,000 Btu ductless heat pump be installed in your living room as quickly as possible. This will prevent you from needing the oil furnace for much of the year. IF you decide to install a water source heat pump to replace the boiler, that will be great, but the ductless system will provide more heat per KW of power in the winter, and also effectively cool up to 200 square meter place by itself, if you open the doors to the living room. Also with the ductless system providing some heat to the house, you should be able to get by with a much smaller water source heat pump than otherwise might be required for your heat load. I don't know your low average winter temperature, or square footage, but say you might be quoted a 48,000 Btu unit to replace your oil burner, the 36,000 Btu unit might work find if you can also run the ductless heat pump to help keep your house warm in the winter. And if one system fails, you have the second one. To get 100,000 Btu's of heat, you can burn 1 gallon of oil, or use 23 KW of electric heaters, or run a heat pump with 5-7 KW of electricity. In America, the price of oil this winter is expected to be above $5 per gallon, maybe even $6 in some parts of the country. That makes using a electric heater seem low cost!

[@waqasahmed939]

I'm considering doing this in the UK. Vailant also have their Arastor which could be used for hot water I'm considering this in conjuction with a small ASHP because : - I could get rid of most of my radiators. I'd still have a couple for the bathrooms - My piping is microbore - Whilst it isn't an ideal solution, I still have gas central heating, before I upgrade to something that can heat water via an ASHP - I have solar PV which would make cooling in summer very close to £0 - The BUS is effectively meaningless to me given my radiators need replacing (even if I stay on gas central heating), and my piping would very likely also need replacing Realistically, more and more homes in the UK will sadly need AC too in the coming decades.

[@dankspain]

It seems you guys have a Fronius inverter, have you set it up for load management for the heat pump? If so any tips on configuration? We are getting our 7,28kWp PV system installed soon and want to configure our 10kW heat pump. Usually uses 1-3kW of power (4 kW max), so thinking on setting up the fronius to trigger an increase in flow and DHW temp when there is a surplus of 2kW. That should increase the self consumption a bunch.

[@benjiro8793]

I feel there are some errors in the argument for Air to Water advantages... A AtA system heats up a room in 5 a 10min, while on low speed. The issue with a AtoW system, is like you said, water containers more heat but it also takes much longer to heat up. As a result, you need to have a stored amount of hot water (what introduces losses over time). While AtW via radiators will keep longer warm, there is no point in radiators giving off heat in the living room, when your going to bed for instance. AtW, you need longer piping in your house to transport that heat (and what will lose heat over areas you may not want heated or that are more exposed to outside. Then add cost ... a radiator, valve, thermostat and other parts, easily go up to 150 Euro. You can find AtA systems that do 3400W for barely 350 Euro. Note: i do not mention installation cost for both systems but you know that a pipe system is way more expensive in installation. Remember, i did not even mention the cost of the AtoW system, storage, piping, only the radiators. And if your house has no piping, good luck with that. That really is something you only want to put in when you build your home. AtoW has the advantage of being a central system with one main unit and more "clean exterior". But your also cluttering up your inside home with radiators, that take away valuable space. While AtoA has a more noticeable high mounted unit, its totally out of the way. AtoW also means that you can ONLY use it for heating. Your summer is hot? Well, time to pony up for another AtoA Airco. Notice how the costs keep increasing with AtoW only setup? AtoW + Raditors + Thermal valves + piping + AtoA (for summer) + Storage + higher installation costs. And worst of all, your relaying on one system dependency. Multiple smaller AtoA systems means if one breaks, you can still tunnel heat ( or cold ) into other parts of the home, until you get it fixed or repaired. There is a reason why AtoW systems are more expensive and harder to find. There is just less market because most smart people figured out that the few disadvantages do not out way the advantages. And i like to point out a massive error regarding boundary layer. Yes, blowing large amounts of air will disrupt the boundary layer around your body, but most AtoA systems run on "silent mode" with very little air movement. We are not talking a massive fan at 10000 rpm. You know what convention is that radiators do? The movement of hot and cold air. Guess why your feet feel cold when your radiator is heating the room? Because your moving the cold air that is at the floor level, what gets moved, as the hot radiator starts to move the air (via convection) upwards. And then you have those cold drafts and people dreaming of floor heating. Because the radiator is disrupting the boundary layer around your feet as the cold air keep moving! That is the issue with people who are used to one system and the disadvantages do not register anymore because they grew up with that system, and think its normal. So when they get introduced to a different system, they tend to list the advantages of that old system, but forgetting the disadvantages, when they compare the new system, as they will focus on the new disadvantages of that system. Very normal and typical human behavior. And its not normal that multiple people need to fight to control the temperature in a room. Sounds more that you have the office AtoA system installed in a very bad location or blowing in a bad way. And forget about ducted AtoA systems, those introduce a lot of other issues (like too warm, too cold, people fighting). Sounds really like you had a ducted system.

[@HeatGeek]

Your misunderstanding the argument. Taking linger to heat up means little to nothing with steady state heating which suits most homes.

[@Volteran]

@@HeatGeek He understood your arguments perfectly. The only one you addressed in the response, linger, he also addressed, as in that you NEED to always warm all the rooms and cannot take advantage of just heating what and when you need the place.

[@jeesjees2]

Water is better because you get better COP with it, but it's also more expensive to put in unless you already have piped heating. Here in Finland we used to have cheap electricity, so we have lots and lots of under floor resistive heating. A good (enough) companion for that has been and is still an air to air heat pump or a mini split. In my experience modern mini splits are very good at maintaining stable temperature. You only get drops during winter where the unit is defrosting. We have two units, both of which have been renewed in the last 2 years. They make up the bulk of our houses heating (not counting hot tap water, obv.). Underfloor air to water or ground source even would be better, but also it would cost tens of thousands of euros to install. Two air to air heat pumps were less than 5000 euros in total, so that's what we're going with for the time beging. I would still prefer water as a distribution method if I was building new, or the house already had water pipes, but it is what it is. One day when we get tired of our tiles and floor boards we will go for water. :D

[@barerfont]

There are combined A2A and A2W heat pumps from a few manufacturers. I was considering this for my renovation with a phase change thermal battery instead of a hot water cylinder.

[@Lewis_Standing]

That's interesting, there's no reason why this couldn't be done and I was thinking it was a bit weird. They are pumping refrigerant around in pipes to a heat exchanger with air - why not also to a cylinder with a heat exchanger on....

[@Macro_Abuser]

I saw a comment about Daikin multi plus doing both. Know anyone else doing it?

[@markingle8487]

Interesting points; we have had independent heat air to air heat pumps (Daikin) in our bedroom and our kitchen/diner for over ten years installed initially for cooling but used throughout the year, and have been considering whether to replace our existing units with an air to air VRF system throughout - we like the simplicity, reliability and the comparatively low install cost; we currently have a normal combi boiler which we use for dhw and background heat. We have done initial calculations but worked out that whilst the per kilowatt hour cost of electricity is so much higher we won't bother changing anything for the time being as it is just not cost effective; the differential between off peak and on peak has gone right down and with more and more people having electric cars I can see this difference getting smaller... gone are the days of 5.9 per kWh off peak! The bathroom is interesting, we have a hhr storage heater in the bathroom which isn't the most efficient, but we like our bathroom warm... so we would definitely want a heat pump indoor unit there. Hadn't really thought about the cost of water heating so your comments were interesting. In terms of noise, no problem at all; but we tend to leave the fan speed on the lowest setting and can't really hear the unit at all. The only time I notice the noise is when in heating mode and the unit goes on a defrost cycle you can hear the refrigerant swooshing about.

[@hearthemermaidssinging8556]

You could put electric in-floor heating in the bathrooms.

[@simonphillips4386]

I have a Midea 5kw split AC unit. The SCOP is stated as 4.2. I chose this over a air to water unit for the below - not cost! - speed it takes to heat the room is much faster than air to water - ability to cool in ever increasing summer temperatures - simplicity of system The unit is brand new, and the issues of noise and varying temperatures are not true with this unit. Much like you have said on air to water heat pumps, the quality of units today vs say 5 years ago has come on massively I am curious though, I'd like to install a mixergy hot water cylinder, and it has a heat exchange for heat pump, is there such a thing as a heat pump that will only heat hot water and not space heating? A video on this would be awesome as I'm sure there are loads of people with these tanks that would like to see a demonstration. Great video -

[@HeatGeek]

Keen to heat or see real world scops.. do you know at what latitude the 4.2 scop is expected?

[@sjcsystems]

Check out a channel called EV Puzzle. In his latest video, Nigel mentions a Daikin multi split system which can have a water heater on one of its ports.

[@michaelmayo3127]

Two different concept, that are both equally very efficient. However, during summer the air to air can also be used as an air conditioning unit also. One disadvantage - of course, if it's a disadvantage? - is that the doors in the house have to be partial open to complete heat the house. Radiated heat contra convected heat, this argument doesn't hold water because all modern radiator are all of the convector type. The chill factor here with regard to the movement of cold air, is being misappropriated; because air to air pumps don't produce cold air when in heating mode, they circulate warm air but, they can also produce cold air. And first, when in A/C mode will the chill factor possibly become a consideration. Air to air pumps also dehumidify living space, so if one has a problem with dampness, then air to air, can in many cases fix a problem. In Scandinavia where the living space for 4 individual is set minimum 120 m2 and comfort is an absolute must, air to air heat-pump for house-heating are readily used and they are not the causes of any discomfort. It must also be mention that water born and geothermal pump are also popular. However, pumps that product hot water are seldom.The argument being; that running an air to water heat-pump during the summer, only to produce hot water, is counter productive. A 100 litre highly insulted water heater, is more economic. We installed a air to air pump in a cellar where there where problems, with dampness. On initial start up the pump produced 17 litre of water a day by dehumidifying. The current production is now only 1.5 litres a day. And the comfort in the cellar has vastly improved.

[@HeatGeek]

Modern radiators are 80% convection 20% radiators at a 70c mean water temperature. However it's more like 50 - 50 on low temperature systems (say 45mwt) which makes the world of difference.

[@HeatGeek]

We meantioned cooling i think?

[@wobnoway5692]

Im happy to do a calibration. Air to air is probably the most efficent. For many reason, which I'm happy to explain but I'd be here all night explaining it on text. Hot water is the biggest issue but there are options. Let me know if you'd like my help 🙂 air temp swings is often setup or controls, A2W has to heat to a condensing temperature, this is the same as your LWT, so A2A is circa 37 degrees, so it's like under floor efficiency, with verible condensing this can then be lower. Regarding thermal dynamics, heating water to heat air is less efficient than heating the air direct. Just to mention a couple of points.

[@HeatGeek]

Do you know what the condensing point of r32 and r290 is??

[@wobnoway5692]

@@HeatGeek 37 degrees is 37 degrees no matter what refrigerant. With verible condensing temperature this can be lowered but it still needs to heat the space. The closer the evap and condes temps are the more efficient the system.

[@HeatGeek]

@@wobnoway5692 sorry in struggling to follow. What is the significance of 37 degrees? We have many systems out below that...

[@wobnoway5692]

@@HeatGeek the normal A2A condensing temp is 37 degrees. Regardless of the refrigerant. Pressure and temperature is related so if a better refrigerant then the pressure will be lower, meaning less energy to produce 37 degrees.

[@wobnoway5692]

If you mean A2W, then the condensing temp is equal to LWT. I emailed you a week ago, Rob from Daikin. We can talk some more. Happy to chat.

[@tivvy-xf4kz]

I don't have central heating. My house is well insulated and not draughty. I looked into getting air to air as a split system could service 4 rooms from the same outside wall. Then I found out any grants were purely for air to water systems and you get no help for Air to Air.

[@steve_steve11111]

Interesting that you don't recommend a2a heat pumps. Here in France, where we're about to have a Toshiba a2a system installed tomorrow, the systems are expensive - euro 8800 but the installers have more experience and know how to properly assess a property. I know that you employ a mixed selection of fitters and as your workforce become more experienced, maybe your opinion will change. I read an article, from a UK resident, who had to find a different installer because everything he requested, he was very negative about his requirements.

[@Hazzer2007]

A2A on paper should be more efficient as it's a fan assisted heat exchanger, extracting the most out of the heatpump. A A2W uses your standard radiators which doesn't actively extract the heat energy. + The argument of the A2A has to heat the air hence not as efficient, it's the same as the A2W, the radiators have to heat the air but without assistance

[@enemyofthestatewearein7945]

The radiators have a much larger surface area hence lower deltaT is possible, UFH even more so. Fan assisted systems always require a higher coil temp even for wet systems.

[@axion8788]

We have whole-house in-floor radiant heat powered by a propane boiler. The unit is near its end of life and will need to be replaced soon. I would like to get an air to water heat pump instead of a new propane unit. My issue is information. I'm in the USA and can't seem to find enough info about manufacturers nor installers. Any info you have about brands (in USA) and any other resources would be much appreciated. Thanks.

[@MichaelPickles]

I'm thinking Daikin vrv with heat recovery and hot water system. I reckon it cost more than 20,000 pounds to get an air to water heat pump in my house.

[@imnothere220]

Sorry to be thick but is there a video on the follow up?

[@stephentaylforth4731]

I had a 2.5 kw Mitsubishi a2a put in our Victorian 2 up 2 down (£1050 fitted). I'm a fanatical energy monitor. Through accidents of history we have plain old resistive electrically heated hotwater (2kw 15 litre undersink heater + electric shower). It costs very little (1.5 kwh per day + shower) maybe we don't use much hotwater. I have a power meter constantly monitoring the aircon/heatpump. Its claimed SCOP is 4.9 which makes it cost comparible to old tariff 5:1 electric / gas cost and my energy monitoring gives me no reason to doubt. But having solar panels it makes it more economical, when my old tariff expires and I get a new one with maybe 3.6:1 electic / gas cost its a no brainer. I'm going to expand it to a 2 headed system to heat the whole downstairs + landing / bathroom via open stair case. The bedroom will be heated as needed with resistive electrical heating. I'm hard of hearing so its silent to me, but people with good hearing say they csn hear it but its not intrusive. Its run on medium fan speed . It was nice to use it as air con during the couple of heatwaves we had in summer. Its mounted blowing down one side of the room so the air movement is barely noticeable.in the room proper Have never noticed any increase in dry skin. It heats up much quicker tha central heating. Directly in line with the blower the temperature does vary by up to 2 degrees Celsius but in the main room its steady to within 0.6 degrees.

[@courtmanr]

Would love to see more A2A content on the channel, look forward to the update.

[@Charlie-UK]

It's not ideal having cassettes on the ceiling for Air To Air Mini Split Heat Pumps. Having the wall mounted units about a meter off the floor seems to be better for heating, because hot air rises...

[@Tim_Small]

You can also stick them up high on the wall, but with the air output pointing at the floor.

[@richardc1983]

Cassette units are not too bad in heating the powerful fans will push the warm air to the floor as the louvres will direct the air down. The best units are the console units which are designed to go where radiators go. They actually have an air outlet at feet level to blow warm air out across the floor. Wall mounts need to be at ceiling level. They have a heating offset temp of 4c due to sensing the temp near the ceiling so in heating with setpoint of 20c they will heat to 24c unti it reaches thermostat off. Having it at floor level will cause issues as the room will overheat as it will not satisfy the room and then take 4c before before it senses that the room has dropped in temp again. Seen it done this way loads of times and it was wrong.

[@Charlie-UK]

@@richardc1983 We have had cassette units operating at radiator level in rooms for years, for heat operating just fine. Very often you don't want fans operating at maximum speed to 'push air down to you' from the ceiling. It's annoying and distracting. And at radiator level, we never have to operate the fans at maximum speed...

[@richardc1983]

@@Charlie-UK are you talking about wall mounts or cassette units that go in the ceiling (like in heat geeks office) wall mounts have a 4c differential in heating mode... They add on 4c in heating mode to the temperature you set due to the height. How far from the ground are you talking of? I may be thinking wrong.

[@Charlie-UK]

@@richardc1983 Sorry, they are Wall mounts. At about, 71 cm or 28 Inches, off the floor. Like I say they seem more effective at delivering heat at lower fan speeds at that level off the floor. For cooling, the ceiling is fine...

[@drsquirrel00]

Are the mini splits really considered air-to-air if they use gas pipes between them? What is the COP of similar mini-split/air to air units? One benefit I think of not having radiators would be saving space in the house, more walls can be used for more purposes. Other solution for hot water showers are electric showers no? yes its 1:1 but there is no heat loss that is generated, they're cheaper, no massive tanks... and then under tap/inline heaters for the hot taps.

[@Bawdale]

Air to air also provides a better air quality in the home. It's filtering dust and slightly dehumidifies.

[@HeatGeek]

Video due on this very soon

[@No_Free_Lunch_Today]

Been thinking why is nobody talking about air to air because the cooling side sounds great. Thanks for the information, so keen to get off gas.

[@ZeroSomeGames]

What about zoning efficiency and agile operation? Although smart thermostats and TRVs exist, I think in practice most homes heated with a water based system tend to treat the home as a single zone (albeit with different set points in each room). In an air-to-water heat pump scenario (especially without underfloor), the heat emitters often won't kick out enough to make the concept of using only the rooms you need to use when you need to use them a bit impossible. Air-to-air cassettes can have a high thermal output and with convection can change the temperature of a room more quickly than that of an air-to-water system. So, if you change your mindset on how to use heating, you could see massive overall kWh consumption reductions by "precision heating" your house a bit more - especially in larger homes with people working from home, for example.

[@loktom4068]

Can you put a heat pump in the interior unfinished basement with an oil burner furnace plus an oil fire burning 40 gallon water heater with over 700-900 square ft. of interior empty basement space?

[@MCSMIK]

I am considering A2A for our 2018 house. To get rid of gas and as I work from home I need air conditioning - the office room is small and the hottest in the house. The hot water is a consideration which is annoying. Reading some comments on here people are saying there are A2A systems which do hot water too, would be very interested to hear more about those and their cost of installation. Getting rid of radiators also is a bonus as they are silly and a waste of space

[@richardc1983]

Yes Lg therma v is an air to water system that will allow you to do both heating and cooling via fan coil units and also hot water cylinder. The also do heat recovery, when the unit is in cooling. The recovered heat is then used to heat the hot water cylinder.

[@johnhunter4181]

Try using the only immersion heater for a while and see what it costs? We turned off our gas this summer and it worked out cheaper using electricity. Heating at night on 20p/kWh for 40 mins is about 2kWh compared to 6.5kWh of gas, running the pilot light for 24 hours and hot water for one hour at 72% efficiency. Okay we have a very old boiler but I don't think there's much in it.

[@speculawyer]

The problem with air to water is that it is not as good for cooling.... and the UK will need cooling in the coming years. But your buildings have existing radiators so you do air to water.

[@HOMEAROMAS]

I just need to add that I'm very disappointed in you, you are usually so good. As you state several times, this isn't factual, it's just your opinion based on the system you have in your office. We don't know how good that system is, how old it is, if it's sized right, if it's run right, if it's been services correctly. You've basically just cast doubt with everything you've said, you've done exactly what Big Oil has done with climate change since the 70s. Shame on you. You should and could have waited until you had data from your proposed experiment, and or you'd gathered more facts/experiences yourself.

[@yscol1313]

You could argue that regardless of the performance of his particular system, everything he said holds true to logical thinking.

[@ricos1497]

To be fair, the video was very open and honest about his limited knowledge. I saw it more as a "reaching out" type video for more information. I have very little doubt that a more detailed video, and possibly a retraction if merited, will follow if someone volunteers the evidence. The heat geek team don't strike me as particularly dogmatic.

[@HOMEAROMAS]

@@ricos1497 It shouldn't have been put out until it's factual, otherwise it's propaganda. And considering they can directly profit from ruining the reputation of A2A, that's not good. I'll say again, I'm very disappointed.

[@HOMEAROMAS]

@@yscol1313 Definitely doesn't hold true to logical thinking. How can he say that heating air directly requires more energy, and then tell you that water takes more energy to heat, and then say it does hold that energy. Logically that water that you've spent energy heating, then has to move through a system losing that energy at each step, heat a big metal rad, and then heat the air that you could have heated directly in the first place. So you may as well directly heat the air in the first place. That's logic.

[@JoostvanderEijk]

@@HOMEAROMAS I hear a lot of facts.

[@imnothere220]

I'm looking at a 75m2 extension. Obviously to be done to modern standards etc but I'm getting more and more pulled to A2A instead of an UFH system. I find the modern builds get very hot (too hot) and the dual function is great. Only fear is not putting in UFH when I'm doing it and losing the option.

[@kaya051285]

Air2Air are a more realistic better option for most homes Getting rid of radiators would be a benefit long term. They don't last forever they cost money to buy initially and to replace every 25 years. The pipework can leak damaging homes, which is an additional cost. The radiators cost lots of energy to make and transport and install Whereas air to air heat pumps can be a DIY project and a broken air to air hear pump is far easier to replace as its cheaper and smaller Also if a home has say 3 independent air to air heat pumps that's more reliable than 1 big wet heat pump Plus the smaller air to air systems would be easier to fit on flats hung off walls than one huge heavy one

[@FloatingIdeasonanarrowboat]

Humidity is not an insulator. It carries heat to cold then dumps it via condensation. What you meant was humid air prevents your sweat evaporation (how sweat cools you) because the air capacity for water is already full if at 100% humidity. Low humidity in an uninsulated house is especially important in winter. And low humidity helps keep you cooler in summer. Just don't go too low or your skin will dry out.

[@TimDaly-k3c]

What do you mean by an efficiency of 300-500%?

[@HeatGeek]

I mean you pay for 1 kWh of electricity but gain 3 to 5 kWh of heat. Look for our video ‘how heat pumps are over 100% efficient’

[@richardkyle5115]

Hi. Interested in advice here. We have a largeish 5 bedroom house. We're planning installation of solar, battery and heat pump to get off gas. Our current central heating is operates, basically in 2 halves from combi boiler. Downstairs we have underfloor heating, perfect for air to water. Upstairs a mish mash of old radiators, mixed bore piping. Not good for air to water. Advisor proposing buffer tank. So, is there any benefit in installing air to air for main rooms upstairs + infrared panels in small rooms and a smaller / cheaper ASHP system down stairs?

[@joshriley9461]

1) noise can be reduced by installing a ducted system 2) cassettes would very rarely be used at home , the purpose of the cassette is the large throw of air it can generate . Roughly 3 meters per vane 3) you can generate hot water and Under floor heating - Check out Daikin or Mitsubishi elective VRV / VRF & Hydro boxes A typical SCOP for a 4kw wall mounted unit 4.71 with and annual power consumption of 1189 kWh Daikin Air Conditioning FTXM42R Wall Mounted 4Kw/14000Btu Heat Pump R32

[@joshriley9461]

*Mitsubishi Electric

[@Tensquaremetreworkshop]

Sounds like an apology for wet systems. Temperature hunting- probably an oversized system. Radiant heating- most low temp rads are multi depth- which does not increase the radiant output. PLUS radiant heat is proportional to the forth power of the temperature- so drops massively with temperature reduction. The vast majority of the heat transfer is convection. You really should know this. 'Very much an opinion based video' - too true! What we need are facts. As a solar array owner, I would put in an A2A system with the water heated via spare generation. EV for storage. Wet systems are last century! why put another step in the chain? Plus, with climate change, the advantage of cooling too is the trump card.

[@Umski]

Think I agree with this summary - same here with PV, have been tempted to stick a small mini-split in for cooling on the few boiling days of the year (full sun) and the few days in the Spring when I have excess solar (beyond dumping into DHW) - if it proves to be a useful and cheap to run addition, I would err on moving to a full on A2A rather than to try an shoehorn an expensive 150kg A2W system into where the boiler is...

[@Tensquaremetreworkshop]

@@Umski Yep- the heat is going from one mass of air to another. Why complicate that with an additional (water) step?

[@barriedear5990]

We have air to air aircon/heating units in some of our shops from around 2005/6. Would replacing them with modern units offer much of an efficiency improvement?

[@richardc1983]

Are they inverter units? You tend to get 15 years on a system so I would say if they've been used every day for that period then they will be nearing end of their life.

[@tomkacandes8286]

It really depends on what you have, model and manufacturer. If they are not correctly sized (i.e. oversized) then that is an opportunity for better efficiency as are inverter driving units.

[@barriedear5990]

@@richardc1983 Not sure if inverter or not. Just looked up the difference online, and can see advantages of inverter which modulates. Will check out make and model on my next visit. And yes 16+ years old, owes us no favours. Thanks.

[@Tensquaremetreworkshop]

Your understanding of radiation versus convection is so far from the physics, you really need to do a thermodynamics 101.

[@davydrav]

How about a radiant heaters from a multi split/vrf in each room much like an oil rad or towel rail but using a refrigerant coil as the element. The refrigerant would be more localized so more efficient maybe. You could also have a separate circuit on the same outdoor unit for your hot water. Also direct to cylinder not piped to a hydrobox and out again 🤔

[@mohibquadri4053]

Great points ! Bro how to gain experience other than traditional ways as hvac site engineer & could u suggest some books to tackle my inexperience in selling service online of designing projects of mep hvac to get initial clients faster also some best read for online money making for service based autocad or revit design engineer, consultants who sell services by creating engineering designs..

[@antwnpowell]

I have a multi split air to air for heating my house. For the hot water I have solar thermal, topped up by ultra cheap electricity , typically about 1 kwh a day. I have an electric. car and solar PV. My electricity bill for a 4 bed 3 storey house here n France.My electricity bill is 77 € a month. I am on my second air/air system , the first I installed myself and it worked fine until I had it replaced by a more efficient system. The air/water seem is more expensive to install and more likely to need maintenance ongoing, plus leaks from the radiators etc..

[@anonymos6254]

Fan coils are a solution for wet systems

[@johntisbury]

Great to hear about this comparison. Thanks chaps.

[@jasonrhl]

Was there a follow up on this where you compared the 2? Im in Australia and want to know if we should invest into a hydronic heat pump - radiator heating system. We are looking at the long game savings. I just cant find the video if you did it.

[@HeatGeek]

There was another called, “were we wrong” which gives more detail.. I prefer wet systems but I think it’s very case dependant

[@jasonrhl]

@@HeatGeek Oh, I watched that one and it was over my head. I was hoping you would have a video showing what happened with the A2A and then how it went with the wet system. I will watch that other video and try to get my brain to work.

[@HOMEAROMAS]

You need to look into A2A properly. The only thing I'd agree with is the issue of heating domestic HW, but you just buy a Mixergy tank for that with a built in PV diverter. A2A systems are most efficient when run constantly, as they run very low and slow, like A2W, so considerably less sound and air movement. You talk about how much energy water can carry compared to air, but that water then has to heat the steel rad, and then heat the air. A2A draws air in through the heat pump, heats the refrigerant, passes this refrigerant to a heat exchanger and heats the air, an A2W system does exactly the same to the point of passing the heat to the heat exchanger, and then heats water, which then gets pumped around a heating system, losing heat to all the pipework as it goes, then has to heat the metal rad, and that then heats the air, which the A2A system did several steps earlier. They are way more efficient if left running all the time. No brainer. And you can run a heat exchanger from them to heat your water.

[@stuartking84able]

So I live in a 45m2 bungalow. No central heating. Electric immersion boiler and electric radiators in each room. I'm expecting to pay £6-£9 per day on electricity in the winter. I'm thinking about air to air as it's got to be better than my current set up. I've seen it is also possible to include air to water for the hot water as part of some set ups.

[@darrenr1995]

Air to air for your heating. It is the most efficient form, with benefit of real cooling in summer.

[@paulmarshall3104]

Hi do air to water heat pumps heat the water in the radiators direct. Or through hot water cylinder

[@HeatGeek]

Direct

[@MrBigbeee]

Very interesting. I’ve seen adverts recently for AtoA that also heat water. Seriously thinking of installing and running from solar.

[@speculawyer]

Or just get a separate heat pump water heater.

[@garywright8846]

I’m sorry I can’t agree, no one in their right mind would install an immersion heater, you can get a heat pump to heat your hot water at a reasonable price. The reason the temperature jumps is you have it too high, set it at say 21, turn the fan speed on low it’ll be quieter and you’ll get better heating. Never run it on Auto. I agree, a major Problem with air heating is it’s only warm when it’s on, where radiators etc heat radiantly, so yes that is better. The main advantage of air to air is you have a cooling system as well as a heating system.😊 Having spent the past twenty five years installing heat pumps in Australia, I know they work and they are good value. I have a fully ducted thermostatically zoned system at home in Perth and it’s wonderful. One thing no one seems to take into account is a heat pump in the UK has to run 24/7 and from about 1600 to to 0900 in winter, a heat pump will continuously go into defrost to stop the coil freezing, this takes on average 10 mins each hour. That’s got to be a big drain on efficiency. Can’t imagine you’ll do a complete house for £8k I think you can double that. As for noise, go for a good make, like Daikin, run on low on heating and you’ll sleep like a baby. Any way, I do love your vids, as a UK heating engineer in the 80/90s I love how things have improved since I emigrated in 95.

[@richardc1983]

Yep and ensure air vanes are pointing down. Unit is likely oversized too if it's cycling on and off. Also set the high ceiling mode to low ceiling height so unit air flow fan steps reduce down... And get it to read the return air at the sensor in the wired controller which removes the 3/4c heating differential to compensate for stratification.

[@jsimnable]

I'm in Canada, my home only has electric resistance baseboard & DHW heaters. I really want to switch to heat pumps to get the savings from SCOP ~2 to 3. Contractor quoted me for an A2A system, but I'm not confident it will evenly heat my many-rooms home. I want to go A2W for radiant floors, but no contractors over here have any experience with A2W and don't want to do it. No rebates for A2W either. Only A2A get rebates :(

[@swmike]

I bought a house here in Sweden, built in the 50ties. Energy need approx 10kW at -20°C. When we bought it we tried to heat 40sqm part with air source heat pump because it had immersion heater heating radiators. I turned off the radiators in that part of the house. This resulted in a really nasty temperature gradient in the room, where it was at least 5°C difference between the temperature by the floor vs temperature by the ceiling. I later discovered that our house isn't well insulated from below, so cold air comes in that way. Now we have a ground source heat pump driving the water radiator system, and the comfort level is back to where it should be. I know others who like their air source heat pumps as an augment, which it surely can be, and I really like our air source heat pump for its cooling functionality, but I'd never go for it as the only heating system in a house like ours. For heating, there are wall mounted air source heat pump indoor units that kind of look like a radiator, that one puts under the window like any radiator. This is probably a much better solution for heating since it takes cold air from the floor and heats it, so one gets the air circulation of cold/warm air cycling through the room.

[@redwhite_040]

Do you have floor heating and floor insulation?

[@swmike]

@@redwhite_040 Floor is insulated, but not draft-proofed properly. No floor heating.

[@100uo]

Having the benefit of cooling in the summer is enough to sway me to A2A.

[@mere_cat]

Good explainer. I was really confused when I first found this channel. What you are calling a heat pump looks nothing like what we have over here in the states. Well, we do have air-to-water heat pumps, but usually only hear of them in commercial applications. I usually only see ductless mini-split installed in homes with hydronic systems and ducted air source heat pumps in ducted oil/gas furnace conversions. Our home is 100% electric, but our ductless unit is undersized, so we need baseboard electric in the coldest months. Fortunately, we don't have time of use rates (yet). But I've been looking into a VRF system so I can add an extra head and ditch our inefficient resistance water heater with only one outdoor unit. Daikin is supposed to be releasing a VRV unit with DHW in the States next year.

[@robincoles1561]

We currently have blown air heating from the 1960's via a massive night storage heater that distributes to all rooms via insulated (could be improved) metal ducting. I've been trying to find out if we could switch the source from the storage heater to an air to air heat pump for about three years. The ducting exists, there's a massive cupboard (where the storage heater is) that could house the heat exchanger and fan unit plus any other hardwear and there's easy voided underfloor space to reach the outside unit. Seems simple to me but I've contacted about 20 installers all over the country and they've all run a mile! We're down in Cornwall. A colleague is having such a system albeit with thermostatically controlled room vents in southern France on his new build. So I'm waiting to see what hardwear his installer uses. Still no good to me if I can't find an installer! We already have solar PV to offset our huge electric consumption (100% electric, no oil, no gas network, no wet system) and divert into our immersion tank via a smart switch.

[@Etacovda63]

What size is your duct work?

[@robincoles1561]

@@Etacovda63 From memory about 150mm

[@adammiles526]

Thanks for having a video on this topic. I look forward to seeing your winter comparison, but when you do please mention that your a2a system was already there and does not meet your Heat Geek design and installation standards. No brands mentioned in the below, this is not an advert. Following my PV installation I had my whole-home a2a multi-split system installed in March this year (2022) for £6k. 10kw external unit, 5kw IR sensing split-vane downstairs, 5kw ducted for upstairs and 1.5kw in the office. SCOP of 4.6 so I'm expecting this to be vastly cheaper to run than the gas boiler, even without PV. Other factors that helped this decision were: -old radiators -leaky valves -downstairs pipes buried in concrete - I was very happy to eliminate this risk before it became an issue! -Upstairs is a heat trap, leading to very hot summer nights. -Desire to do things properly and avoid moving a portable heat pump around the house Previously with the gas boiler and multi-zoning with eTRV's the rooms would often overshoot by quite a lot as the system had no weather compensation and was unaware of how hot the loop already was and thus its' calculations were way off. In comparison to that, this is a lovely even heat everywhere with no noticeable temperature swings or discomfort. Thankfully it is nothing like sitting in a room with a fan heater. On the DHW side I was planning (long-term) to have an unvented cylinder, but I then found out about heat batteries which require no servicing and feel like the future of hot water. Due to the unexpected realisation that my immersion only heated a tiny fraction of the modern cylinder and wanting to eliminate gas usage I brought the plan forward and now hot water is provided by a heat battery. Cold mains pressure in on one side, hot mains pressure out the other with no internal storage. The ~75 degree output goes through a thermostatic mixing valve before distribution. I'm lucky to have plenty of PV and an environmentally-conscious family, so not concerned about only having 100% efficiency there as I don't think I would actually notice the a2w efficiency benefit there. I can provide more details if required.

[@darrenr1995]

Look like you had good advice regarding the air conditioning. We install gas fired and refrigerant systems. We find our customers wanting AC more and more and less of the other tech we can provide. For hot water, don’t over look point of use hot water heating. Not exactly efficient but the only operate when water is drawn through so daily electrical consumption for a normal sized house substantially lower than stored water heating.

[@HeatGeek]

Awesome feedback thankyou!

[@shanewilliams4603]

Actually, there is an underfloor radiant air heating system developed in Canada through a company called Legalett.

[@tomkacandes8286]

Thanks for this thoughtful and reasonable review, Heat Geeks. You left out a rather LARGE difference in your comparison: refrigerant line sets carrying refrigerant are relatively fragile and A2AHP’s rely on very good installer technique and testing in order to work properly over a proper lifespan. A multi split or multiple splits can require 4-9 line sets, each one having four flare joints that can easily leak, releasing enough GWP CO2 equivalent from R410a as the unit might have saved in CO2 through energy savings over its lifetime- ta da, climate value negated. A2W HP’s mostly have either factory sealed refrigerant lines within the condenser ending at the plate heat exchanger or very short line sets to a main indoor hydronic distribution unit. In the US, we have an inverse universe where air-to-water HP’s are rare and not well known (or commonly incentivized!) and people commonly use “Air Source Heat Pump” when they mean Air-to-Air because that’s what’s known. The cylinder top style heat pump hot water heaters work but are often stealing heat and dehumidifying in spaces where that’s not so great to do, but the DHW piping happens to be. Keep up the great work, Tom in NY

[@Sean006]

Tom, it was great to hear your thoughts....especially from an area of the world with real world experience using A2A heat pumps. It highlights the importance of installation and probably also the quality of materials & design used in the manufacture of the HP. I guess there is no such thing as a free lunch.....but some people are expecting lobster dinners when they may get a slice of pizza!!

[@Sean006]

@@zlmdragon. But there is growing evidence that the recent increase in global temperatures is linked to human activity....namely greenhouse gases from human activity. You might disagree but the scientific consensus is that we do change things!!.....perhaps it is too late to correct the damage but it doesn't mean we should give up. Be positive, we can make a difference!!

[@Kregorius]

Dude, if the house has radiators or underfloor heating, the mini split air to air wouldn't make sense. Or vice versa. Like this house I am living in. There is no wet system or radiators. No underfloor system to hook in. Options are air to air or remodeling the whole house to get those radiators or floor heating. Yes it ain't the best, but rebuilding a house to fit something else in it won't be the best either. For a comparison: there are four air to air heat pumps in the house. And three wood stoves. Rebuilding one woodstove to modern standards cost more than those four heat pumps and a years electricity to run them. There is some math to run when remodeling old houses.

[@HeatGeek]

Yo! In the UK the vast majority of homes already have wet systems dude.

[@elisabethbowman8075]

@@HeatGeeknot in the highlands and islands of Scotland. No gas.

[@chrisolsen4578]

The air can be colder with air to air because you move the hot air in the ceilling down to your feets.

[@HeatGeek]

This is incorrect. More air movement breaks down your boundary layers so air temp needs to be hotter for the same level of comfort

[@chrisolsen4578]

I am aware of the boundary layer, it also helps to distribute other heat sources such as a wood burning fire who tend to rise to the celling espesiisly when there is air leaks in the floors wich many houses have.

[@evdabbler]

Recently discovered and subscribed. Very useful videos to demistify some simple principles with data and facts. On this occasion it does feel like an initial opinion (ie an hypothesis) based on a single sample at work, which will need further testing. It seems that the overall efficiency of air to air means it has a real role to play in decarbonisation. How about a more comprehensive field test. Pick a location with similar houses on same side of a street (similar insulation, same orientation, same sun exposure) and install air to air, air to water, IR, maybe even tepeo in separate volunteering houses for this trial. Keep some combi boiler control group house. Measure all stats including temp at which customers run the house. Finally lay on top qualitative feedback.

[@johnhunter4181]

I think you're being too kind.

[@evdabbler]

@@johnhunter4181 ah ah. Only give the feedback in a tone you'd be keen to receive it yourself I guess!

[@pjmorgan]

Our house is a three-bed semi built in 1971. It's got double (and some triple) glazing throughout and it now has full-fill cavity wall insulation and reasonable loft insulation. The heating is currently oil-fired (with an ancient boiler) and we have only one bathroom with an electric shower. The only DHW demand is the kitchen and bathroom sink. The radiators are for the most part small, old and all fed with 10mm microbore. My view is air-to-air would be perfect for our house, as the radiators and pipework are unsuitable for an air-to-water system and there's really no need for any DHW system. I'd just get a boiling water tap for the kitchen (one that does hot and boiling water) and put in a point-of-use heater for the bathroom sink. Thoughts on this?

[@chrisspychalski2376]

if you're concerned about refrigerant leaking, there's way more opportunities, probability and volume in AAHP. Refrigerant formula change will not effect AWHP. by including end of life replacement costs at year 15 for 30yr ownership you'd see advantage. DIY/low cost labor can handle non-refridgerant parts.

[@goldengame6813]

Is your unit an inverter though? I’ve got a 12,000 btu DC inverter system, runs at 34db on quiet mode and similar with the outside unit. It’s very good at holding a steady temp. I had fluctuations with a standard unit before.

[@thomasl2974]

We have have a ground heatpump and under floor heating as well an accumalating fireplace and a wood stove. The investment cost today would b around 30 k Euros. The heatpump got replaced after 21 years at a cost of 11 k Euros. Our energy plus electicity bill is around 2500 euros per year.total energy need is around 25000 kWh per year including household electricity for heating 240 sqm and providing hotwater for 4 persons. SCOP of the heat pump is sligthly above 4. We have had so for over 20 years. I tell this because your comparison of cost of the air.to air is kuch kore favoruable than comapring the initial cost. You need to include the replacement cost of the system. Replacing the air to water or ground heat pump is much more expensive compared to air ti air. The water to air heat pump will last you 15 to in good cases 20 years. The air to air will need to be replaced omre often though. This needs to be concidered since life span of the house is more yhan 20 years. Another factor is the service cost. The air to water system has more components, that is more expensive parts to replace if it breaks. Ageothermal heat pump will be the most costly to service. I live in the Nordics and here the geothermal system is a now-brainer if you huild a new house with under föoor heating were there is jo central heating available and the house is over 160 sqm. For smaller houses I would tend to lean towards aiir to air plus a sufficient large hot water boiler that can be heated during cheap electricity hours. Gas is not an option here but we have a third option firewood or wood pellet. Both of these can be used for heating the house and water. Amodern fireplace have very high efficency and do not have to be extremly expensive. We have one as well.