How to Stop Damp Mould & Condensation - a COMPLETE Guide

[@bobbobson4069]

This is by far the most comprehensive "documentary" on the phenomenon of damp/mould and how to reduce it. I really appreciate the astonishing amount of work that has clearly gone into the making of it. The science and home experiments are fascinating. I can honestly say that I really understand the whole phenomenon much better now. Well done! I have of course liked and subscribed as a result! (Marius Gudonis, originally from northwest London, but now working in Warsaw)

[@YellowPinkie]

As a building services engineer, I can state that is the simplest and easiest to understand explanation of RH. Good work Charlie!

[@CharlieDIYte]

Thanks, Stephen I massively appreciate that!

[@andrewstones2921]

I agree with Stephen 100%

[@npr1300A8]

Brilliantly explained. Thank you.

[@joeslacker1020]

​@@CharlieDIYte Hey you say to have a ventalation system or an Air Conditioner to circulate the air, but what if it's in a rainy area and you have a heater on with the AC or it on fan mode in a travel trailer? I thought the cold air from the outside meeting with the warm air inside is what causes the moisture, so why would putting air from outside inside cause it to be less moisture?

[@kenleehk65]

Perhaps to add a bit more accuracy to that statement..."Relative humidity is the amount of moisture in the air relative to the amount of moisture air can hold, influenced by its temperature "....yes, the air pressure also plays a part in how much moisture air can hold at atmospheric conditions. However, changes due to elevation and weather may contribute to a certain extent, though not massively.

[@markbriggs729]

Another +1 for PIV. I Moved into an early 1900's bungalow in Essex a few years ago and humidity levels were getting up into the 80's through the first winter. At one point water was streaming from the single glazed windows, down onto the windowsill and puddling on the floor. You could sense it in the air as well, everything would feel damp and there was a constant musk. I installed an extractor in both the kitchen and bathroom and changed all the single glazed windows to double and although this did help with the build up on the windows it didn't have much effect on the levels. I then tried running a dehumidifier and although this was somewhat successful it was only whilst it was running. As soon as it stopped the levels rose again. Last year i went with a loft fitted PIV with no heat and almost instantly the levels dropped down into the 40's. Even through the worst of winter it only crept up to 60% a few times. I have it fitted in the hallway and you can notice the temp if you stand right under it but it's a small price to pay for having no condensation or mould in the house. It even seems to force the air into all of the rooms quite well under door gaps etc. I now have that running all year round, use extractors in the kitchen and bathroom and put the dehumidifier on next to the clothes horse when drying clothes inside in the winter with amazing results. Quite possibly the best purchase i have ever made. If anyone reading has similar issues in a similar property i can't recommend them enough.

[@MTechOver9000]

Hi Mark, I came across you comment here, thanks for this info. This was made 6 months ago, would you still recommend the system you have? Which brand did you go for? Many thanks in advance

[@That1ufo]

After a flood they say it takes months to dry out with dehumidifiers, was the house empty not heated when you moved in? The clothes horse was probably the biggest problem or rain coming in the walls, get a condensing dryer!

[@pavel9652]

The line of logic regarding dehumidifier is flawed. You wrote it was somewhat successful when running. So is the piv, because it somewhat works when it is running. I think there is another problem, just like people suggested, it was damp because being vacant for a long time or there is a leak. Check the plumbing. I lived in the house where there were THREE small leaks simultaneously, under the main hot tank, shower and the small hot tank in the kitchen. That had risen moisture levels significantly in all the locations without producing obvious signs of leak.

[@JayL123]

@markbriggs729 Would you need Trickle vents on the windows for PIVs to work? None of the rooms have ventilation holes in the wall but have trickle vents in the windows. We plan to change the windows and I wonder if I have to get tricke vents in it for the air to flow. Apologies if its a silly question, but the trickle vents are all dusty and mouldy.

[@lynnfincham6839]

I have PV has helped but had to do many other things to control mould ect. Think every house has its own individual probs. I run dehumidifier too. With extractor fans bathroom kitchen. I don’t ever dry washing indoors tho ever. So much water your introducing back into the property. Dry on line as much as possible. Even put washing in summer house not main house. 😊

[@SloopyDog]

I was born in 1947 we lived in a council house with a coal fire. We never had any damp or mould problems. We had an oven in the kitchen linked to the coal fire. My mother often dried clothes on a clothes horse put in front of the oven, and still no damp problems. We didn't have radiators all we had was a back boiler behind the fire to heat the water. Coal fires allowed the house to breathe. Later on, the council fitted a gas boiler and radiators. That's when the problems started, we started getting damp problems, the windows were always damp on the inside. Many years later I had a Housing Association bungalow, due to my health problems. The Housing Association in their great wisdom decided to insulate the loft to the current standard. A damp-proofing firm filled the cavity walls with insulation( pumped in). That was when the bungalow started getting damp problems. Mould started to appear on every wall. It became a constant battle to keep the walls mould-free. The windows were always streaming with water. My wife and I are in our late seventies and in very poor health, I try to keep windows open as much as possible, all the time in summer. We are causing more problems by having our homes over-insulated. The house needs to breathe. Cavity walls were designed to do just that. There is no great mystery as to why people have damp problems. Many people can not afford to heat their homes as due to an incompetent government fuel prices have gone through the roof. People on minimum wages and pensioners on a single basic pension, like myself are struggling to live. In this country, the rich get rich and the poor are forgotten about. The basic pension starts at £130, you don't get far on that. I would like to see if the Prime Minister or our overpaid MPs could survive on what I have to live on. THERE IS NO WAY THEY COULD.

[@CharlieDIYte]

Sorry to hear about the problems you face now and thank you for explaining how the situation has changed over the years. It was makes perfect sense given the need to ventilate houses.

[@steffananthonyholden2752]

The problem is there was no clear strategy initially with insulation measures - now under Pas2035 the government intends to rectify all of this - “there is no insulation without ventilation” which is the causation for most your damp and mould symptoms … measures installed in isolation never work effectively - there has to be a conjoined approach and strategy …. Much in the same as if you improve a cars BHP you must improve its breaking capacity …. The old open fire houses had a mass of ventilation via the stack so RH never had time to condense and air changes were at a rate of 2/5 …. Of course the only way to heat the property was with fossil fuel and this is now to be banned …. And just to add , the mechanical operation of ‘opening windows manual will never work , nor will trickle vents long term

[@kevinwalsh8483]

Got a stove fitted before Christmas used to have an open fire.. windows are destroyed now due to the chimney been blocked now. Always had clothes on the rads drying.. so annoying

[@zane___k7333]

Because the fire gives off a lot of infared heat. Which reduces relative humidity.

[@user-bz9cb8bp2y]

We have candles, gov calls it affordable heating in UK 😂❤️❤️🇮🇱

[@mikebarber458]

Hello !! I've been a Master HVAC contractor for 30+ years and I really liked you explanation of dew point and RH . I have many clients in a high rise condo building in a very mixed climate of Richmond va. Floor to ceiling glass walls on one or more sides. The windows are double pane but the framing is aluminum. I've been dealing with the frames condensating for years. Dehumidifiers as you said solve most of the problem, but coupled with air flow from floor fans and or ceiling fans solved the rest of the issues. Combined they totally eliminated condensating. I've automated some Dehumidifiers to work in conjunction with the air handlers fan. I got excellent results

[@corvoattano9303]

Hello. From reading your comment am I correct in assuming that high airflow around areas where condensate builds up helps to mix it back into the room air which can then be removed using a dehumidifier?

[@lh3690]

Seriously one of the best videos on this topic I've seen. I'm new to being more humidity aware due to issues at our trailer. This explained things so clearly and to the point that I feel like I have a much better base from which to address our issues and less anxiety about unknowns.

[@CharlieDIYte]

So glad to hear that. I recommend getting a hygrometer, that way you know where you stand and what steps you need to take. 👍

[@alanedwards9069]

Moved into a circa 1900 mid terrace stone house 3.5 years ago, had major issues with condensation for around 18 months until I installed a PIV. Stopped it dead. Within 2 days I put away the window vac and it’s been there for the last 2 years. Installed over the staircase and the only time you feel cold air is when walking up the final flight of stairs (three storey house). House went from 80%+ humidity to between 40-50% virtually overnight

[@philipoakley5498]

what size was it & was it costly? (even if in retrospect it was the best pounds spent ;-)

[@noneB974]

total price with breakdown please?

[@markkendall6854]

Another vote here for PIV, a landlord of an end terraced old house with no cavity I the walls, spent a couple of grand fitting insulated plasterboard on the inside of external walls. Even lent the tenants a quality dehumidifier, but only fitting the Nuaire PIV solved the problem. It cost me a good tenant too, trying actively to resolve the problem. Property is now condensation free. This will be my go to solution 1st step in future.

[@BarnzyHQ]

Did your insulated plasterboard become wet ? Or was that dry before you fitted the PIV

[@jesshothersall]

My life changed overnight when I bought that Karcher a few years ago. My Crittals turned from opaque waterfalls to windows in one hit, and the bonus is, I'm cleaning them daily with distilled water, as the karcher moves over the glass. Not only left dry, but also clean, what a result! We already opened our decent size bathroom window, daily and I have a condenser drier, but you have to leave woollens on a rack, and denims too. Interesting and informative video as always Charlie, thanks very much :)

[@CharlieDIYte]

Great work Jessica. You've pretty much got all bases covered there. Could be with buying a hygrometer just to keep an eye on moisture with that stuff hanging up to dry but doesn't sound like you've got anything to worry about 👍🏻

[@TK42138]

Quite possibly the best condensation advice video on KZbin.

[@CharlieDIYte]

Thanks 🙏👍🏻

[@davidiand7]

Excellent video Charlie well done! I’m a Brit living in Sweden, all houses here built in the last 50 years or more have some form of ventilation system, be it natural draught ventilation pipes from kitchens and bathrooms, fans in the roof drawing air out of the house 24/7 (my current house has this, it works well, some windows still have the original paint and the house was built in 77). I have lived in a house with a heat exchanger, this would be my system of choice, I have known it to be down to -15 outside in the house +22 and the radiator was hardly on, you could hold your hand on it without it burning. (Heat systems are a little different here but that’s another subject). People do not use heavy curtains here, they are normally not drawn, they are light weight net curtains and for decoration purposes. Usually Venetian blinds are installed between the glass pains in the case of triple glazing older style, or you can have triple glazed window with an envelope with a vacuum and an envelope with argon gas which are great, sometimes they have condensation on the outside and when it really snows, it can lay against the glass for days without melting, I currently have both types installed all windows have ventilators built into the frame which you can control, I never have condensation. Having said this in this part of Sweden the RH is lower than the U.K. which is surrounded by seas. When it is a minus temperature outside the RH can drop dramatically I have seen the RH as low as 20% which is not so comfortable, at the moment I have 45% and it’s -3c outside. I have an alarm system which has smoke detectors with temperature and humidity sensors, even when I am not home I can see the humidity and temperatures in the house on my phone. As you say condensation can destroy your home but more importantly your health! Incidentally the main heating system I have is a warm air pump, they are a like an air on unit but push out warm air, it circulates the air round the house and can be used in the summer for cooling but it’s expensive to do that, I do have it on when it is hot sometimes. Sorry this sitt is in Swedish but you can translate using Google www.bast-i-test.se/tester_pa_basta/luftvarmepumpar.html

[@speedfinder1]

I've had a PIV system like the one you show, since 2010. It inputs into the central hall directly above the water radiator. It has vastly improved the moisture problems in my 1930s solid brick house. I still have other systems in place, but it is a good percentage of the solution to my damp issues in the winter.

[@thepaintedsock]

Hi. I had one installed recently. It made no improvement to humidity after a week. Have you actually measured yours? Before and after?

[@speedfinder1]

@@thepaintedsock Sorry, I didn't do any Before and After recorded tests. I just know that the damp smell in my house went away after a while with the PIV system running continuously over about a 6 month period. There is a chance that you may have to be patient to see any measurable improvement as the humidity content in the atmosphere in your home may be being kept high by residual humidity in your soft furnishings, or in fact the buildings structure. "Air Conditioning" of any type does take a while to show any real results unless it is working inside a sealed water tight box. This isn't a cop out answer but in my modest experience, these things tend to need either to work in conjunction with a refrigerant or dessicant electric dehumidifier for faster results. Good luck! 👍👍.

[@mosmes02]

@@thepaintedsock if you don't have anywhere for the "stale" air to go, you won't see a difference, you need ventilation such as weep vents or air bricks.

[@Noor-kp1yb]

Does the filter need changing ours isn’t working as it was before the bathroom is drenched after showers and even just washing hair over the bathtub!

[@paulfletcher7227]

I had a PIV installed a few days ago, and there no has been no condensation on my windows since

[@DennisMcDermott]

I fitted a PIV unit a couple of years ago in my bungalow, this was in January, the next morning I had no condensation, and have not had any since. It does not make the area where it is installed cold, brilliant system.

[@simonmccutcheon7085]

Hi, which system did you have? I am looking at one by envirovent

[@JamesScholes]

Thank you for this video. I finally decided to take action on your advice and to stop breathing altogether. Breathing has been the root-cause of many of the problems in my life anyway. For example, I stubbed my toe the other week and afterwards it dawned on me if I wasn’t breathing this would have never happened to me. I’m also getting tired of inflating my lungs only to deflate ‘em a few seconds later (I mean seriously, who’ve got time for that?). Anyway, your video was the final nudge I needed to take action and I’ll be sure to credit you and your video regardless the outcome. Thanks again.

[@CharlieDIYte]

James, James you need to START BREATHING AGAIN 😬 Very drole but I hope you found the video useful.

[@annaartesana2622]

Funny

[@alexonfilm]

I'm right there with you. F'ing hilarious.

[@thequaintandquirky]

Love this 🤣

[@janettemajo2205]

Hilarious don't stop breathing please😁😂

[@matthewharding89]

We have a 170 year old terrace cottage. Modern render, windows and plaster. We tried everything. Even without changing our habits with the shower, cooking, boiling the kettle and drying clothes, we installed a PIV unit and the results have been dramatic. We've gone from up to 80%RH to

[@geoffwoollen]

Great content on the fact many people cannot understand that inside air at 20C at high RH contains more water than outside air at 5 C when its raining 100% RH. This means you should also mention :- This is why you need a water vapour barrier on the INSIDE of the walls. (VCL vapor control layer) Otherwise water vapour will penetrate into the brick and condense leading to mould inside the wall. Especially single skin walls. You cannot get at the mould inside the wall to kill it off so it will become a permanent damp and mouldy wall. Timber frame houses now use a sheet of plastic. In other words it does not want to be breathable on the INSIDE but must be breathable on the outside. If you have used polystyrene backed plasterboard thus will act as a VCL. Emulsion paints are breathable and not a VCL. So use a suitable primer or paint to establish a VCL. Builders who do not understand RH will tell you wrongly that old walls need to breathable.

[@CharlieDIYte]

Thanks Geoff. A valuable bit of commentary. Unfortunately my walls were all tyrolean rendered in the 1970s, so I'm pretty fastidious at keeping some sort of ventilation with windows open somewhere at all times. I fear some of the earlier insulated plasterboarding I did wasn't perfect from a vapour control/ cold bridging point of view but you'd be amazed how few builders understand this. I had one round recently telling me how he'd insulate the downstairs on a building project I've got planned and his vapour barrier planning was non existent.

[@1212haro]

We gave up purchasing the larger dehumidifiers as they were only lasting us a year on average, regardless of brand name. Instead we purchased the table top models, one for each room and two for our unfinished basement. These little power houses have completely solved our high humidity problems. We hare removing 1/2 to 1 inch of water per day. One of these units is already 3 years old and still working like a charm!

[@CharlieDIYte]

Great work. Glad to hear it's solved your humidity problems👍

[@guydickinson4640]

Thanks

[@CharlieDIYte]

Thanks Guy, really appreciate that. Also here's the update kzbin.info/www/bejne/hJPXmp1-gN5ljNEsi=-3HmqGJOZTgIfraZ 👊

[@mayhemuk88]

Removing the wife n kids helped alot especially when they have a bath/shower, ooh too cold to open the window, great video and well explained

[@RichardNutman]

We had an Envirovent PIV installed. The house we moved into was extremely humid, loads of mould growing on the metal window frames, and in cold corners of bedrooms. It completely solved the problem 100%. The electric it uses is minimal, few pounds a year. It does warm the air if it's cold, but it also has the effect of pushing down the warm air from radiators that collect at the top of the stairs, so the net result is it doesn't cool the house. Totally silent and no condensation on windows at all. Washed jeans even dry inside in record time! :) Our downstairs is quite open plan, so the air coming in does circulate quite well. We got the control unit with it, and after the moisture level of the house was sorted, we just run it on trickle mode now, only turn it up if we're drying several loads of clothes in the same day.

[@CharlieDIYte]

Thanks for this Richard. I'm going to install one in time for the winter. Just mulling over which manufacturer to go for but I'm interested in what you say about the Envirovent. Was there any particular reason you went for this over the Nuaire or Vent Axia?

[@RichardNutman]

@@CharlieDIYte No particular reason, it was the 1st one I saw and didn't know there were others. The model they do now is newer than the one we have, but it's still working great. Just had the filter on it changed few months ago. It can feel a little draughty at times, as our main sitting area is below the stairs where it's located, which is why we insisted on having the remote to turn it down. Normally they set it to normal and you don't get the remote. But I think the new ones integrate with a smart phone app.

[@johnrussell5245]

I fitted a heat recovery ventilation system in our barn conversion 18 years ago. It was the best money I ever spent. I've fitted it in other dwellings since and I'd go as far to say I'll never live in a house without MVHR again. It should be mandatory in all new builds. I've never come across a house that can't be retrofitted, with a bit of effort and the will to do it. They might cost (£4-6,000), but they're easy enough to fit by any competent DIYer. They should be a priority ahead of frivolous things like fancy cars and expensive holidays. They will improve every day of your life spent in your home.

[@rtaitm]

High praise, but how does it improve your life so much?

[@andrewstones2921]

John Russell is correct that MVHR is the answer, and having fitted it 18 years ago he was well ahead of the pack. I work with MVHR daily, but the company that work for now only install MHRV in new build houses. It's perfectly correct that with effort you can retrofit virtually any home, but to work at it's best the house should be airtight and insulated to a very high standard, and typically that's not practical in an older home. In the course of my work I have seen poorly installed MHRV by builders and well installed MHRV by DIY'er, but typically a retrofit has so many constraints on the type of ducting you can use and the optimal design layout that whilst very worthwhile and a huge benefit over not having it, it almost certainly will not approach the effectiveness achieved in a new build with an equally high standard of airtightness and insulation. The bottom line here is that all new homes SHOULD have MHRV and the cost is very low if installed at the right stage in the build.

[@dave2166]

@@rtaitm simply they continously extract the stall stagnant moisture laden air with fresh filtered and tempered air...whilst recovering upto 90% of the heat energy....24/7. They will be mandatory in new houses within 5 years id say if the government are truly serious about nett zero carbon aspirations

[@andimoraru5539]

As a civil engineer, I would like to say thank you for the scientific and evidence based aproach. Keep it up! The condensation problem is of insulation, wall permeability that has it roots in the design phase of a house. There are no issues of this kind in a biocomoosite material house ( hempcrete, light-straw-clay) because it insulates and alows the walls to breath in the same time, while lime prevents mold to develop and keeps pests away from the wood frame. It's a fire retardant solution as well because it covers the timber frame and prevents it from burning.

[@CharlieDIYte]

Thanks Andi, really appreciate that. My last update is a little more coherent on the general ventilation strategy kzbin.info/www/bejne/hJPXmp1-gN5ljNEsi=JmwfKs89VToo3hwg

[@Sarhatabaot]

Perfect timing on this video. Just started looking into a mold problem we have in the room next to a shower.

[@CharlieDIYte]

Glad to hear it. Hope you find it useful!! 👍

[@eternallearner4753]

I installed a Nuaire Drimaster PIV unit three years ago. In winter, the area around the unit is a little cooler, and in summer, a little warmer. There were no extractor fans fitted in my renovated cottage (now remedied), and every morning all the windows had to be severely Karchered! Now I can't even remember where I stored the Karcher. My decision to install the PIV unit was also made as it is claimed they reduce radon in a building (the cottage is in Cornwall and its walls are granite). I put the drier rack in the smallest bedroom and dry the clothes very successfully with the help of the ebac dehumidifier (I have a tumble dryer, but not the bank account to support it!). Great video, amazing research. Subscribed!

[@CharlieDIYte]

Wow, you've totally nailed the problem and you're so wise to have a dehumidifier to deal with moisture from drying the clothes. I don't have major issues here with the RH levels at a pretty constant 45 to 50% but I'm so tempted to install a PIV just to keep things circulating and to minimise condensation on the remaining, single glazed windows, as the reviews on them here are unanimously positive. Out of interest, I'm guessing you still get congregation when you shut the curtains? Thanks so much for the comment and for subscribing 👍🏻

[@dudleyjoseph9485]

Great video. I'm another advocate for PIV. I've got an old house which had elevated humidity levels mainly we think due to a few original flagstone floors. Mainly solid walls with minimal or no insulation also. PIV has almost completely solved condensation problems. You do need to make sure however that the source of the air in the loft space is drier than within the house and to do this, you really need to be thinking about absolute humidity levels rather than relative. The best PIV units will measure absolute humidity and turn on and off as they need to. Generally, if your loft is reasonably ventilated from outside, you should be OK. Location of the PIV is also critical. Needs to be as central as possible. Some house layouts wont work. In addition, you may need to encourage the air movement through to the rooms that are further away from the unit possibly by installing additional passive vents. Definitely need to keep doors to rooms open and ensure that the PIV is not 'short circuited' by having any existing extractor fans close to it. Yes, the air coming out of the unit can be chilly and will cool your landing down but it doesn't seem to affect the rest of the house. You would not want a unit dumping air directly into a habitable room. Go and take a look at Pete Ward's channel for a wealth of stuff about humidity in older houses and absolute vs relative discussion although he doesn't appear to be a massive fan of PIV.

[@afnankhokhar5578]

Thank you for such a detailed response. Very helpful

[@steffananthonyholden2752]

Also trim your doors 10mm from the FFL to allow free flow of air movement

[@gortagnan]

@@steffananthonyholden2752 Thanks ..makes sense but just to be sure ..FFL meaning F (?) floor level ?

[@JuiceBanger1]

final floor level. ie after you have laid the tile or lino etc. i discovered this term when installing a bath and bath panel. it just means leave a gap or shave the door to get a gap@@gortagnan

[@theshemullet]

Thanks!

[@CharlieDIYte]

You're welcome 👊

[@h9rae]

I suffered from damp and condensation in one room downstairs ,this i found out was due to no fresh air getting into the room/ fitted 2 vents at floor level direct to the outside and one at the top, problem solved no damp no condensation , the trouble is people seal up everything to stop draught a big mistake /good video very informative

[@ja5837]

An excellent video on condensation, one thing that we have found living in a stone house with thick walls and built with lime is that when you live in a valley as we do the humidity outside is nearly always higher, thus making it harder to get the reading down, the way old stone and lime buildings work with thick walls is the walls absorb the wet and it dissipates it when the weather is dry, sunny or windy, we find the best way to get the inside humidity down is to coat the outside walls with a liquid sealer like water seal, what that does is allows the walls to still breath, dissipating the damp but actually seals the stone from the wet, this makes the wall drier and warmer and the inside humidity level falls. This stuff is not cheap and there are online demonstrations of how it works.

[@chrisofnottingham]

I was told about PIV units by a customer of mine while I was doing unrelated work on his house. It cured a chronic mold problem he had in an upstairs corridor. The customer tried various things without success and had been reluctant to spend so much money on installing a PIV unit. But in talking to a guy who fitted them, the fitter said if it didn't fix the problem he would pay back all the money himself - for the PIV unit and the fitting - that's confidence! When I read up about them it all seemed too good to be true and I remained somewhat skeptical. Then a mate started to get mold around a bay window in his flat (ironically, because he had it renovated and it was no longer draughty). The management company installed a PIV unit and it all cleared up. I still can't really believe they work but the only two cases I have encountered personally were both successful.

[@seanbrett76]

We installed a PIV system, whilst it did reduce the condensation issue it didn't resolve it. The landing is now rather cold for little benefit.

[@chrisofnottingham]

@@seanbrett76 Do you know why there is condensation?

[@seanbrett76]

@@chrisofnottingham I blame the missus! No matter what I say she'll leave the door open whilst having a shower. Other than that we don't have room for a dryer so use clothes horses 😣

[@Largeone1968]

Another vote for PIV. I’m a landlord and the go to solution for lifestyle damp is a PIV. Go on any landlord page and you’ll see the same answer time and time again. In the six years that I’ve been fitting them, the Nuaire have gone from £260 to just shy of £400 for the heated unit. This is no doubt due to popularity. They just work. They’re absolutely silent unlike dehumidifiers. They’re much cheaper to run than dehumidifiers too. What’s not been mentioned is they help allergy sufferers by the filtered air driving out pollen, dust and mites. I’ve had to block up certain air vents close to the Piv due to air taking the path of least resistance. Highly recommended

[@truth952]

Where do you install them? I think a PIV would be a solution to one of my rental properties which has significant damp in cellar to the point it’s recently been affecting corners in living room. Am I best to put PIV in the cellar by air brick or put it in loft ?

[@baldeepgill7916]

I completely agree we had a bad cause of condensation in our rental property and our tenants complained alot. Then, eight years ago I came across PIVs and I got a nuaire installed and I must say it has worked 100% and I also have a mr venty envirovent installed installed in ours too. Now, we have acquired a new property.. We have noticed the internal glazing is soaked in water. Will be investing in a piv here too before we get tenants in. Prevention is better than the cure. A nuaire got installed yesterday and checked it out. boy is it a bit noisy..hope it settles down. Going to ensure that within the tenancy agreement the tenants are not allowed to meddle with it.

[@dave2166]

@@truth952 they mostly go in a loft for a house... however not every house suits a piv...most do. The only true way to understand its suitability then a free survey from someone like envirovent will tell you all you need

[@andrewriley4204]

I've fitted one. Think of a PIV like the car windscreen demister. That blows air over the windscreen (basically a window) & provides a clear view without Condensation. Problem is, we add heat to the blower in cars, simply for our comfort, who wants to sit there freezing? Equally the standard NuAire PIV is a cold blown air so stairwells will be cold unless, you add the bolt-on heater or start with the model with a heat unit Cheers, Andrew

[@dave2166]

@@andrewriley4204 they should not be folded without the heater.... my company doesn't. Even though the top of the ceiling above the stairs will be the warmest air in the house youre redistributing that air and shifting it elsewhere.

[@declanpboles]

The best presenter I seen in a while and knows his stuff. Well done.

[@fabmanly1070]

I you have an attic, you can install a Positive Pressure Ventilation system. How many of you run your Bathroom fan 10-15 minutes after you’ve finished? Probably very few (you need to completely cycle through an entire room of air). PPV system is like having a tube running into your house from the roof. Imagine putting a large super hose into this and pouring water down it rapidly, your house would start filling up and eventually water would find its way out through the cracks in your windows/doors as its under pressure. That’s what a Positive Pressure air system does. It will work its way through the house forcing out stale damp air. Your house needs that change of air constantly to avoid stale stagnant air. Its called cycling, and you need to work out your volume of interior living space so you can install the correctly powered system that will cycle the correct amount/volume of air for your home. Your furniture/ clothes/ lounge suite/ mattresses (can hold anything up 10 litres of water-water! Wow imagine sleeping in a bed with 10 litres of water in it!) must be purged of this moisture before you will be healthy. So the system will take a few months before you truly have a healthy home, but you will notice it after a few days with the firs at signs (no weeping on the windows). Leave cupboard doors and any spaces with closed doors ajar so air can flow. Its all about air movement and pressure.

[@markwilliams5654]

most Fans have a built in timer or humidistat

[@JayL123]

@fabmanly1070 Would we need Trickle vents on the windows for PIVs to work? None of the rooms have ventilation holes in the wall but have trickle vents in the windows. We plan to change the windows and I wonder if I have to get tricke vents in it for the air to flow. Apologies if its a silly question, but the trickle vents are all dusty and mouldy.

[@fabmanly1070]

@@JayL123 Had to look up trickle vents. We don’t have them in New Zealand. Air, like water will always find the easiest exit point. We never had any of that in my homes with PPV’s. Talk to an installer near you. We also have two positions for our handles to be positioned on our windows, so they can be left ajar if needed, but still locked. Air will always find a way out. New windows are good and bad. Good to seal, but bad because they are so good at sealing up. But as you say, you have these extra vents that sit hove your windows.

[@cwiddowson1]

Wow, comprehensive with a capital 'C', thank you! We have an old French house with single glazing, solid stone walls and no damp course (there's a complete disbelief in rising damp over here). That said, the bottom 6" of virtually everything wood - stairs, skirting, door frames etc. had virtually disappeared due to rot with corresponding mould in room corners. I put this down to how the previous owners used the house for a few months then locked it up and left it for several more (over a period of 60yrs). After a couple of years of living in the house full time with a big focus on letting it 'breathe', damp does not seem to be a problem other than condensation even without any curtains. For this we've started copying our French neighbours who religiously close all external shutters at dusk. Voila, no condensation (or light for that matter). Thanks again!

[@CharlieDIYte]

Yes, closing the shutters will achieve a lot, because it's raising the temperature of the pane on the outside, meaning nothing can condense against it on the inside. Glad to hear you're getting to the bottom of it. 👍

[@markandfionastilwell2323]

Installed PIV units 6-7 years ago and our condensation problems disappeared. No issue with cold draughts or temperature. Our house is circa 1900 stone with slate roof and double glazing. Have had several family and friends install them and all have been really impressed with the difference.

[@CharlieDIYte]

Thanks Mark, yes, there's universal love for PIVs in this comments feed. I think I'll be installing one next winter (too many videos in the pipeline to do it now!)

[@brownesugar1000]

Sounds great how much did this cost please?

[@pah9844]

Hi Charlie. I was OCD with damp windows, mould for years, drive me mad. I even changed descent windows once thinking they weren’t that good. I then saw NewAir ad for PIV and had one fitted in my loft above my stairs. Best thing ever. I’ve had it for 4 yrs and never get condensation or mould in any rooms and I live in a 4 bed detached. I bought the switch to warm the air slightly and don’t have any issues with this, maybe use to it and it doesn’t really cost anything to run. I’ve also used a dehumidifier for years to dry clothes overnight. Works wonders.

[@CharlieDIYte]

Thanks Paul. That's great to hear. Yes, I think a PIV install might be a good summer job for me!

[@geoffgeach6804]

I have recently had an Air Intake and Extraction system installed by Envirovent of Harrogate which draws air in through the Back wall of my flat and out through the front running constantly. The increase to my electricity bill is negligible but the difference in the flat is ABSOLUTELY FANBLOODYTASTIC!! I can not praise Envirovent enough.

[@gillian417]

Not obvious. So helpful. I've spoken to several tradesman who've never offered this advice. THANK YOU and now a subscriber.

[@CharlieDIYte]

Thanks Gillian. I did an update video a few weeks ago kzbin.info/www/bejne/hJPXmp1-gN5ljNE I appreciate the sub 👍

[@Joelk2666]

Recently installed a drimaster after having condensation and mould issues. It has made the hallway colder but has cured my condensation issues

[@MurrayC]

Me too, the version without the heater. It makes the hall a little colder but that's no real hassle. RH is 50% with 90%+ outside RH.

[@prizecowproductionspresent4463]

As a semi retired Glazier that worked in England for 3 years i understand the problems you get in your houses. Like Mr Cooke i found this explantion on how to deal with Humidity and air flows to be spot on. The fact that i bought a house that was built nearly 70 years ago has given me the understanding of solving such issues as is always the case when old details meet new lifestyles. Once again you have proved that youtube is a wonderful research tool if you take time to find the relevant information. Aussie Jeff

[@CharlieDIYte]

Good to hear from you Aussie Jeff! I appreciate that. There's a lot of love in this comment feed for the Nuaire or Vent Axia PIVs. Totally eradicates condensation. Can you get something similar in Oz?

[@stevesmith3395]

I have had a Nuaire PIV HC unit installed and running for over a year. I can say that it absolutely transformed our excessive moisture and condensation problem within hours. I wish I had purchased the heat element one but understand they still dont warm the air up enough. I experimented a little and have found that setting three is guaranteed to stop the moisture build up and stop mould growing. This does chill the air locally somewhat when temperatures drop. Setting 2 seems to be a happy medium where you barely notice a chill and it keeps moisture down. I tried setting one but in winter you will see a small amount of condensation return in perhaps a bedroom furthest from the unit. So I an now sticking with setting 2 and will introduce a bit of ventilation to the bedroom door. I need to do a bit of work to improve the insulation around cold spots at the edges of the upstairs ceilings. I initially changed the loft insulation as excessive insulation without sufficient ventilation causes this in a lot of older houses. Just a bit of tweaking to get the balance right. This PIV unit has been vastly superior than the dehumidifier that I still have as its effects are very localised. I cant recommend a PIV unit enough and they are cheap to run. So much better for my health. I developed asthma since moving to this house. The mould used to keep appearing but does not anymore. We used to get it in wardrobes and cupboards, even downstairs there would be furry growth on boots and handbags. It was truly awful but it has been eradicated and only my sons bedroom got tiny mould spots after I experimented by leaving the unit on the lowest setting. In summer it may cut out due to high temperature. Dont worry if the temp drops again and it doesnt come on. It can be four hours or something before it comes back to life after too high a temperature.

[@baldeepgill7916]

We have a nuaire in our rental and a envirovent Mr venty in our home and going to buy a nuaire in a new rental we have acquired as it has a bad case of condensation.

[@jazzyman4]

In running a UPVC window and door company we issued instructions in order to keep condensation to our customers The instructions included and explanation of the amount of water we breathe out at night and the importance of ventilation when possible The UPVC windows are must more draught sealed and therefore keep the moisture in In our window we installed trickle vents at the top All the suggestions on his video are excellent and should be followed

[@CMDRSloma]

I'm a fan of DIY Home Automation so I bought cheap Xiaomi Aqara Temp/Humidity/Pressure sensors, now I measure all of them around the house and everything is parsed to the database. In the bathroom, my fan turns on when it needs to turn on - to reduce humidity and not when you switch the light on. Sometimes it turns on by itself when there is a spike in humidity. Home Assistant is amazing for automating stuff like these but I understand this is far beyond the scope of this channel. Luckily I don't have too many problems with humidity, it stays around 40-60% in winter, the house is insulated and the windows are double glazed.

[@CharlieDIYte]

Very cool indeed. You should install this for landlords. You'd make a fortune!

[@arronth]

We've had a Nuaire PIV unit in our house for many years. (1960s bungalow) and it has improved our winter condensation problems massively. Ours doesn't have the heating element, so it does make the hallway quite cold compared to the other rooms of the house, but as it's a hallway we don't spend much time in there, so we live with it. You make a really good point about shutting doors. For PIV units to be effective we've found that we have to keep all internal doors open at might to let air circulate, otherwise in the morning the windows are streaming with moisture.

[@CharlieDIYte]

Thanks so much for that Arron. And if you leave the doors open, the windows are totally free of condensation?

[@arronth]

@@CharlieDIYte Yep, if the doors are kept open then the windows are completely dry. The only time this isn't the case is if we happen to have a sudden dip in temperature overnight for example, then we may find a small band of condensation at the bottom of the windows.

[@tellylgeorge]

Great video Charlie. Very helpful and informative. I did all the same research a few years ago as I was having some issues with condensation and mould in my bungalow. I installed a good centrifugal fan in my bathroom and ducted my kitchen extractor to outside. But I also installed a PIV ( the one pictured in your video actually) and it has been great. My hygrometer rarely goes above 40 RH. I've set mine on a low fan speed which seems to change the air enough for my place and it certainly doesn't create a cold spot in my passage. When you put your hand up to the outlet you can feel the draft but this isn't enough to create a cold spot in the hallway. You can't feel any cold air when stood directly underneath the outlet. I haven't noticed any significant increase in my electricity bill from the fan in loft running constantly. When the loft temperature increases in the warmer weather the unit switches off as it is thermostatically controlled. All this said I really do think that your lifestyle habits are the main influence because you do have to manage the air inside your home as best you can. Keep up the great videos.

[@ravi5602]

Positive Input systems - I have a rental property and the tenants are forever drying clothes on rads, under heating the property and never opening windows. This resulted in literally puddles of water on window sills and black mould growth on external walls. After trying a lot of different thing we installed a c£400 positive input device and I must say it is BRILLIANT! Totally cured the damp problems in a 4 bed double glazed 1950's student house and they pay the electricity bill. I was amazed it was so effective.

[@ravi5602]

I should add it the heated version...

[@CharlieDIYte]

Thanks Ravi. It's rental properties that feel this most acutely because you can do so much to manage humidity through lifestyle, which a lot of tenants, particularly students aren't going to be focused on (I certainly wouldn't have been back then). I'm not surprised you've found the PIV to have been so effective as I was introduced to them originally by a friend who has a couple of rental properties. What I am surprised about is where all that moisture goes. I suppose it's constantly diluted by the cold, drier air coming in, and whenever someone opens a window (rare) or front door (less rare!) the house breathes a sigh of relief and belches out some of that humid air.

[@axers22]

Thanks for the video. I've got a PIV without the heating element. It does make the whole house a lot colder during winter. If curtains are closed and no trickle vents are installed then it does take a while to get rid of the condensation. I've put it on a smart plug and turn it on during the days the weather is dry and wet clothing is drying. It does indeed make clothing dry faster!

[@spencerwilton5831]

axers22 a good condenser dryer is far more sensible than drying clothes on racks when line drying isn't possible. People complain about the running costs, but the advantage of a condenser dryer is that they push heat into the room which partially offsets the heat required from your boiler.

[@tomcarroll2622]

Great Video Charlie, thanks. I live in Ireland in a 1970s bungalow. We have problems with high RH and damp. I was frustrated after installing a triple glazed window that even then I was getting condensation on the inside glass! The same with all my double glazed windows. I am about to install a Drimaster PIV. I also need to take steps such as reduce the moisture from the kitchen and bathroom. I am using a De Longhi dehumidifier which works great when drying clothes etc. The more I learn and understand the less problems I am having with mold and damp!

[@karl3721]

I am an electrician and I have fitted several nu aire piv, the customers all rave about their effectiveness I would definitely put one in my house if it wasn’t for the loft conversion. The heated version is a must.

[@77superboss]

Hi Karl, I’m a landlord based in Nottingham! I’m having some condensations issues in my block of flats. Mainly the top floor flats with lofts above them. I’m considering installing one of the PIV units however have been told I may need to also run a hard wired fire alarm from the device as it will be on a top floor flat. Could you also let me know what specific PIV unit you would recommend?! Thank you! Best wishes.

[@karl3721]

@@77superboss I have used nu air, they are on the internet based in Wales

[@paulhillman8299]

We have had a Nuaire PIV for about 6 years. Within about 4 days after the installation, all our condensation problems disappeared. The house is old (~1900), brick and we added and amended it to 5 bedrooms for what became a large family. Damp in the walls was always a problem but since the PIV has ben installed, there is no mould or discoloured paintwork. You can hear it when on the maximum 6 setting but soon get to ignore it. In all we are very pleased with it.

[@CharlieDIYte]

Thanks Paul. Yes you and many others have extolled the virtues of PIVs in this comment feed. I'd quite like to install one here. Could be an autumn job if I get everything else done. Also presumably it provides a bit of cool air on summer nights?

[@isyt1]

I live in a 1930s Scottish house and have gone through the same experiences and research as you have with similar results. Insulation and ventilation is key and we run our dehumidifier regularly, especially when cooking and drying clothes beside the wood burning stove. When showering we open windows at opposing sides of the house to flush out the moisture. Also important to fill any holes and cracks on the exterior walls that are letting water in.

[@CharlieDIYte]

Thanks - it's always good to hear enterprising solutions from people in a similar situation!

[@Beany87]

One thing to add which is obvious but worth pointing out to anyone still on the fence about a kartcher vac, you can use it on the bathroom tiles and shower doors to increase the efficiency of quickly lowering the humidity in the bathroom, the less standing water (close toilet lid too) the less humidity able to evaporate into the air. Great video. Looking in to reflective insulation behind my rads too :)

[@ollydearden]

I put a PIV in last year and it's been bloody brilliant (I'll leave the manufacturer out, so you know I'm not spamming) No condensation on any window in my single glazed, 1930s house. The house also smells fresher upstairs, but not cold. The house also heats up much faster.

[@gekcho]

Hi Olly, can you tell me which brand of PIV you bought and what part of the world you live in?

[@baldeepgill7916]

We have nuaire drimaster in my rental and a envirovent Mr venty in our home..will be getting another nuaire for a rental we have acquired.. Don't want headache of complaining tenants. Kid you not it is the best investment we made.

[@liberalmediabias5893]

I have an issue with extractors in general. The lower pressure gives me headaches. I know of another person who could tell the extractor in the office was on for the same reason. So extracting the humid air during a bath doesn't work for me. Also, with athsma, it feels great when you inhale steam. I just put that out there. Sometimes expressing what the obstacle is, is half way to overcoming it. Great video. Very clear. Thank you.

[@CharlieDIYte]

Sorry to hear that, mate. It's a tricky one this because I totally hear what you say about the asthma, but humidity is so bad for buildings. I guess get a couple of hygrometers and try and keep that humidity around 60% or below. Thanks for the comment 👊

[@rpcrev]

Very timely video. Thanks for that, so insightful. And my contribution to the discussion is- We have just had a positive air pressure system fitted to the loft by our landlord. We had terrible damp problems despite doing many of the measures you outlined. So in conclusion 1) It did work. Noticeable fresher cleaner air and less damp and mould in corner bedroom. 2) sadly our smart meter has gone crazy. Maxing out in the red almost everyday compared to sometimes being under budget.. . 4 kW heater is clearly the culprit. 3) Our hallway is never particularly warm but I would say it feels a little cooler. But not substantially. So it's doing a great job but at a very noticeable cost due to the heater. Obviously, years down the line will involve servicing issues too.

[@ohmydog9]

Your videos have been so helpful and have taught me how to master the humidity and mould problem in my flat. We are very careful about controlling humidity like keeping the bathroom door closed - I’m always yelling at people to close the door! We are also lucky to have a window in the bathroom. Have opened all our trickle vents and automated a dehumidifier to run each night. When I see the RH sneak above 60% I open the window, even if it’s freezing, if only to ventilate for 15/30 minutes. No problems this winter! Thanks so much. Your videos on this topic are the best I found.

[@matthewgurd6477]

Great video, about two years ago we did similar research and decided on installing a nuaire PIV in the upstairs hallway. Humidity levels dropped in the problem room from +70% to 50-60%. We chose the heated PIR and did notice chilly air being pumped at the start so we do increase the heat in the winter. Electricity bills were not drastically impacted.

[@EssGeeSee]

I concur. Only run our PIV at night.

[@abutw0]

I have read that as moist airvin house, naturally rises to attic, there is a risk that that very same humid air can be pumped back into house. Similarly if attic is vented via eaves etc. Fresh air in Attic can also be very moist.... Any thoughts?

[@Coxy002605]

@@abutw0 Moisture naturally rises with warmer air to the ceiling, where it gets trapped. The fresh air coming in from outside is almost certainly of lower humidity than the air inside the house.

[@GurungyNoHamuster]

Some Meaco observations. We got the one you show ages ago and used it in the laundry room to good effect through the whole house. When we first dehumidified there was humidity in books, upholstery, carpets, etc. which declined to normal over a couple of weeks. The Meaco started leaking in cold weather after a few years so it was relegated to a garage. A second Meaco dessicant (same model) did exactly the same (be aware they are impossible to open). We now have a Meaco compressor (same size) which is by far the best. We track energy use quite closely and none of them were significant, and all did a great job with humidity.

[@frederickwood9116]

Nice work. I have obsessed about Relative Humidity values for a number of years. It’s not something that people find easy to understand. So explaining it is not always successful. I think you got it down nicely. Personally I think every house in our climate should have a dehumidifier but the concept is not widely understood. I have not played with many brands but I am a Meaco fan. I have bought both desiccant and compressor versions. My research found compressor ones seem to operate best around room temperature and the desiccant ones are best in colder spaces (15 c down to -10 or so) The desiccant ones tend to warm a room slightly which may be an advantage in some situations and can explain the extra running cost. I highly recommend a dehumidifier as a clothes drying solution in our UK / Ireland climate. You get good results for less cost than running a tumble dryer (I have seen bills drop significantly) as well as rooms/houses being healthier. The best drying results being where a largeish desk fan is also used to move air through the clothes rack even just at a slow speed. Also your don’t need to use the clothes drying setting but it will day things faster. I like the compressor dehumidifier you have there. Nice controls. I may have to try it out if I need to get another one some day. Thanks again. I’ll be sharing this when the topic comes up.

[@raftonpounder6696]

I have a Nuaire PIV which I unfortunately had to stop using. I live in a bungalow and it made the whole house very cold in the winter. The installer placed it very near my thermostat so the heating ran constantly because the thermostat was telling the boiler that it was freezing! The other problem I found with it was in the summer the whole house smelt of the loft! It’s a shame because it was very effective at reducing moisture in the house in the rooms where the doors were open. My four teenagers would not keep their doors open so their rooms were still damp, mouldy disaster zones! I bought a Meaco condenser dehumidifier last week and wish I had seen your video first. I would have bought the Ebac instead. The smart mode looks like an excellent idea. Another brilliant video by the way. Thank you.

[@CharlieDIYte]

That's a shame. I could have a similar problem in my loft which is so dirty and full of flies I'd have to construct some sort of box to put it in. You could install a smart heating system like I did here kzbin.info/www/bejne/r6bbiHd5h9x8q8U which would remove that thermostat from the situation. Also, with the teenagers rooms you have to cut 10mm off the button of the doors so that you have circulation even when the doors are shut.

[@raftonpounder6696]

@@CharlieDIYte we had lovely, expensive oak doors fitted a few years ago. My wife would not be impressed if I took a plane to them!

[@209porker]

We have a PIV in our 130yr old house. It is a large 3500sq ft. property with no insulation and thick walls. The condensation and RH have reduced significantly since I installed it a few years ago. I also noted the price seems to have crept up significantly. I have the heated model but never wired the heater up. I note that another well respected you tuber who posts a lot about damp issues is sceptical about PIV but I think as our roof space is well ventilated (read has loads of gaps) I think the colder dryer air in the loft is pushed through the house meaning the wetter air gets pushed out. I also insulated an exposed bedroom internally that used to suffer from condensation on parts of the walls and this has cured the problem.

[@CharlieDIYte]

Thanks Matt - that's interesting and confirms what I heard when I was researching this. The insulation makes a massive difference, doesn't it. You just have to ensure you don't create any child bridges when installing it, which I didn't completely do in my son's room. Still, he had mould everywhere before and none now. Thanks for the comment!

[@miatrue98]

What does PIV stand for? Thank you

[@Nickgowans]

I work in building facade design, working primarily on very large commercial or residential buildings. You're absolutely right as far as the building physics go and the reasons for condensation. In terms of "dehumidifiers" they dont really work so effectively unless theyre working constantly which is an expensice way to solve the problem. The biggest thing in building design in terms of condensation risk is appropriate placement of insulation as well as the vapour control layer which allows air to pass through but not the moisture. If you have adequate insulation, great, but unless you can control the movement of the moisture in the air through the wall cavities you will end up with some interstitial condensation problems, where the moisture simply moves into the wall cavity resulting in long term mould. The buildings I work on have a vapour control layer usually placed just below the internal finishes which stop the moisture in the air from ever reaching the insulation or cavity. It allows the passage of air, but not the passage of the moisture. This stops the warm damp air from contacting the cold surfaces, because the insulation is on the outside of this barrier. Edit: its very important to remove the interstitial condensation risk, because by moving that condensation into the wall cavities, over long periods of time will result in structural damage if its not controlled.

[@Tephnos]

This is more of a concern for modern airtight buildings. Old leaky ones, especially in the UK, don't really have to concern themselves with interstitial condensation too much (which is why builders here don't give a damn about ensuring airtightness of a VCL), because all the air leakage ensures any condensation dries out quickly.

[@geoffaries]

Hi Charlie another of you excellent videos, I've been involved in heating and ventilation for more years than I care to remember, but have seldom seen the issues so well explained, it is so good that I've sent your link to the company who manage my rental properties :-) I've been giving this type of advice for some years, but not so well as you have done. There is a caveat, which concerns the optimum level of humidity, I suffer from a form of bronchitis in the winter and have found that the best humidity for me is circa 55%, my doctor suggested putting the damp washing in the bedroom! but being an engineer I elected to use a humidifier where I can accuratley control the humidity. I have found that modern well insulated properties can have humidities in the 30 - 40% range, which dries out the mucous membranes inside of humans, more serious than chapped lips! I have also been involved with the design and installation of MHVR systems and one of the problems is in maintaining them e.g. people don't clean/replace the filters regualarly and they can introduce low %RH air into the house which will reduce the house humidity. I use the Meaco in my "man cave" where my toys live, because it seems that most of the refrigerant types are not very efficient below ambient air temp. of 15 Deg.C.

[@markbrown1412]

Hello, I live in interior Alaska. I am in the process of building and have the good fortune of being near the cold weather climate research center in Fairbanks. I must say, your video is spot on regarding this moisture/ventilation issue in the home. Understanding what the dew point really means cannot be Overemphasized. Your video covers these issues in a very helpful and informative way. I am a retired environmental chemist, have a good grasp of the subject matter, and have seen people insulate their homes in ways that contribute to this problem. Even though My education should make me an expert on the subject, it does not. I had to modify my home plans after consulting with the people at the cold weather research center in Fairbanks. My ideas about properly insulating my home were misguided. People get information from KZbin, their neighbors, and their friends, believing they are doing something good for their home, when in reality, they are actually making their moisture/ condensation worse. Why? Because they are getting bad/inaccurate information, and they don’t understand the concepts regarding air temperature, humidity, and dew point or relative humidity. Building practices that work in warm/hot climates probably will not work in a cold climate. I learned this upon moving to Alaska. Thank you for your well done And spot on video.

[@WisdomIsPrecious]

What specifically are the mistakes ppl make that you learned about?

[@ianbrowne8871]

Living in a 1980s house but in a conservation area, no extractor fans are permitted in the bathroom or kitchen. When build secondary glazing was fitted to the modern sash windows but given drafts and traffic noise, owners applied draft-proofer which stopped any attempt to ventilate. I was able to replace these windows with modern conservation grade UPVC double glazed sash windows. It meant being able to ventilate in recent very hot weather and acts now when i use heating less. Replacing the bathroom and having a shower room I made the mistake of having another heated towel rail which is to be replaced with a radiator because with all walls tiled, every surface was creating condensation - even with windows open! A very useful video when one might have heating on for just an hour or two at the most!

[@CharlieDIYte]

Good work Ian with the windows. It's ridiculous you can't have extractors in conservation areas. That's the world we live in 🤦 I guess dehumidifiers are the other option.

[@surreyarborist]

This bloke is talking a lot of sense here now subscribed

[@andrewfallon2719]

Brilliant video for people like myself who don’t know much on the issue. I have just bought 3 hygrometers as a result of this video. If the humidity is above 60% I shall buy a window vacuum. Thank you so much

[@CharlieDIYte]

Great work Andrew. It really is half the battle actually knowing what humidity you've got. Window vac good but ventilation (opening windows) and managing all the vapour you generate cooking and bathing to make sure it doesn't circulate around the house is the most important part of this.

[@lukewokeywoos]

@@CharlieDIYte Charlie i have an ebac dehumidifier but when bedroom door is shut on a night the windows condensate up as they’re 20 years old. I tried the salt trick and it actually works. Make sure to put behind any blinds or kurtauns

[@RichardsModellingAdventures]

We have a PIV unit in our bungalow. It fixed the problems we had with damp over night. No problems with cold air at all. We just run it very slow

[@DerekHundik]

piv whats that ?

[@bmatic2069]

@@DerekHundik Google PIV Ventilation - loads of information!!!

[@nattybking]

I wish I knew all of this info 6 years ago when me and the husband first moved in together. We had terrible problems with black mould and condensation in our previous 1950s house and my husband has asthma and other allergies too. We now have 3 small children and despite moving to a newer property (built in 1990) we are once again seeing mould building up on our windows and walls and the condensation is just ridiculous. We do have a dehumidifier and that has helped but we are seriously considering a PIV also. Thank you for taking the time to make this and your more recent video on mould issues, the information is the best I have come across both in delivery and also content. 😊

[@CharlieDIYte]

You're very welcome. Yes I think you should definitely get a PIV installed. Well done getting the dehumidifier. I wonder where the mould is coming from in your case. Do you hang a lot of washing up inside/ generate a lot of moisture from baths etc?

[@nattybking]

@@CharlieDIYte we're not entirely sure to be honest, we have a heat pump tumble drier, I use a clothes horse for a few items, but not that many, we open the bathroom window after showering each night etc. Our garage door leads off the utility where I dry the clothes and we put a seal around the door frame last winter as it was bitterly cold round there and my husband thinks that that could have made the issue worse. We also drink a lot of tea and coffee, so that could also be a factor. We have no trickle valves on our DG windows and the extractor in the kitchen is one of those pointless ones that isn't on an external wall. I think there was already mould there and the previous owners painted over it to sell the house. We've only been here for 18 months and it's only recently that we've started noticing mould on coving, windows and walls. Whatever the reason, it is a big no no with 3 small children and a husband with allergies.

[@StuckInTheM1ddle]

Excellent video, full of obviously well researched info that you have to put a lot of time and effort into. Don’t worry about the length, I much prefer the complete story rather than you breaking it into small chunks. My wife thought I was mad when a dehumidifier arrived recently to deal with all of the indoor clothes drying being done but she’s now an evangelist after seeing how much water it removes and how much quicker the clothes dry. Keep up the great work that saves me endless hours having to go down a rabbit-hole myself on 😀

[@CharlieDIYte]

Thanks Mark - yes this was quite a brutal one to put together, about 175 video clips in my editing folder and I still missed a couple of things!! Wise move on the dehumidifier. Did you buy it because you were having mould problems?

[@StuckInTheM1ddle]

@@CharlieDIYte I wasn't haven't mould problems in the room it's in but we have been drying a lot of clothes in the room given the time of year and I wasn't happy with all that moisture going around. I actually bought several of the Thermopro's a while back and saw how high the humidiy was getting in the room where the clothes drying is so bit the bullet and bought one. I found the below website a great resource when researching on dehumidifers and condensation in general . The guy who runs it really goes deep on his research too. www.fixmyroof.co.uk/videos-and-guides/condensation-cure/best-dehumidifier/

[@alfindigo]

We live in Brittany France which is renowned for high humidity and damp houses. We suffered damp and condensation in the house when we bought it and there was evidence of previous occupants trying to stop condensation by covering outside facing walls with polystyrene insulated wallpaper. It didn’t work. We removed all this and redecorated and had new double glazed windows with external shutters. If we left the house empty over winter we returned to damp furniture and mould growing in corners. We fitted a basic PIV system which helped reduce damp but in winter it brought in cold air which cooled the walls under the PIV and attracted condensation! Later we fitted a newer PIV with a heater element and now all our condensation mould and damp had gone. We can leave the house empty in winter and it is dry on our return. ( the PIV runs all the time. We have used dehumidifiers but they don’t work as well as the PIV.

[@CharlieDIYte]

Thanks for that Allan. Yes PIVs with the heater to temper the air coming in are the way forward. I'm going to install one here before winter, if I have time.

[@jeffhalbo96]

Excellent analysis of this issue, Charlie, thank you! Our experience of dehumidifiers totally bears out your endorsement of them, especially for laundry drying but also for general control of the RH in our home.

[@eastsharp]

Great video! I just bought a hundred year old house with single panes in a forest. I learned everything the hard way!

[@andrewadam4989]

I've added Positive Vent systems to two of my houses and find they work very well. There is certainly a chilly spot directly underneath but I don't find that it makes the general house spacer cooler or cause me to have high heating to compensate. I used to have a dehumidifier and find that the PV system works much much better.

[@rossmanning4863]

Andrew Adam I’ve got one with a heater on it. Does the job.

[@dave2166]

Its the perception of air movement which makes you feel its colder... a fan on a hot day when its 30c will make you feel cooler even though the air passing over your skin is still 30c

[@vitalmakhdum]

this guy's channel is bloody brilliant

[@CharlieDIYte]

Aw, thanks mate 🙏👊🏻

[@Smithb83]

Another excellent video Charlie, chock full of well researched info to help us homeowners overcome DIY issues. Love your channel 🙌

[@arthursoutham9046]

Hi there. I found your talk most interesting. I am South African and when I came to England I noticed a number of things in the houses there. 1. No air bricks in the upper parts of the outer walls. In all the houses in SA we have 2 airbricks built into each room. 2. We in SA do not go in for shower rooms. We also site the bathroom on the outside wall. In other words we always had veneration to the outside. 3. Curtains were never hung in the opening of the window. We had lace curtains against the window, but the main curtain was hung about 2 inches away from the wall and about 4 inches from the window. This allowed ventilation past the window. We still got condensation on the windows, but not to the same degree as in England. This could be attributed to the fact that the outside air temperature never got much below 10 degrees, although while I was in the army in Bloemfontein it regularly got down to -15. Even then we did not have heavy condensation on the windows as there was good circulation through the bungalow. I know because it was freezing. I fully understand where you are coming from when you say that circulation through the house is crucial in stopping mould and condensation. But I can understand why airbricks are not installed in European houses. It's just too cold. So it looks like dehumidifiers are the way to go. Limit the amount of moisture in the air and circulate the air via the crack at the bottom of the door. Another thing I found with the houses in England that if the rooms down stairs were heated it all went upstairs into the bedrooms, while the heated lounge remained cold. All the window condensation occurred upstairs in the hot part of the house while the cold part remained relatively condensation free. You explained this in your talk. Thanks for a most interesting talk on this topic of damp in the house. Would you believe it the problem is worse in Italy than it is in England. I repainted the bathroom of the house where we were living in Italy. After killing the mould and sanding the walls and ceiling till all traces of mould were gone I painted with an oil based paint to seal the walls from moisture. That winter the mould reappeared and pushed the paint off the walls and ceiling. Now I'm stumped as to how to stop this happening. In England I retilled my bathroom and repainted the upper part of the walls and ceiling with an eggshell PVA. This seemed to cure the problem.

[@CharlieDIYte]

Thanks Arthur for such an in depth comment. Not sure what I can suggest for your Italian property. kzbin.info/www/bejne/r6ulo2p9qJigobM In this video I tested a wall with bad air circulation and moisture with Zinsser BIN and their top coat that has an in built biocide and the results have been impressive. So that is an option you might consider.. Could you install a PIV?

[@leeholke9851]

My job is a water damage and mould restoration. And u have done ur home work well done.

[@CharlieDIYte]

Thanks Lee - I really appreciate that and it's always good to hear positive feedback from a pro!

[@charlescp1558]

It’s a while since you posted this, but I thought I would say we installed an Envirovent in my daughter’s 2 bed flat and it solved damp and mould problem overnight. Can also dry clothes on airers very quickly. No loft, so mounted above entrance door and draws air in through a hole cut in acrylic we swapped the glass out for. Fantastic product, not cheap, but works and very low running costs, was teamed with their humidistat extractor serving bathroom and kitchen. Keep up the good content!

[@sibat777]

On the Kettle front, I’ve bought one of those units that just boils one cup of water at a time, it reduces the steam in the kitchen dramatically. The reservoir only needs refilling 6-8 cups of tea or coffer (and it filters the water too). It’s quicker than boiling the whole kettle for one or two cups too!

[@CharlieDIYte]

That's really interesting. Which one is it, out of interest?

[@sibat777]

@@CharlieDIYte this is the one I bought, there are many others but this one balances price with quality well imho www.amazon.co.uk/gp/product/B002NGNRHC/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

[@CharlieDIYte]

@@sibat777 Thanks! I'll be buying one of these. I wouldn't have known it existed without you so thank you for that 👍

[@sibat777]

@@CharlieDIYte 👍 good luck, I did think about the Quooker instant hot water tap but that was too expensive, same concept but no need to refill.🧐

[@jotttn]

Sibat 777 - that’s fantastic! This is just what I have been looking for

[@mikee2773]

I've had my PIV fitted for about a month now. I live in a 3 bed detached bungalow with very bad condensation. This has been a game changer. Absolutely no condensation. Ive got the heated type PIV, so the cold zone is only marginal but when the main central heating is on you don't notice it. I have my PIV connected to a smart plug with energy monitoring. It's left on 24/7 and only costs 25p per week. The PIV heater pulses on every 3 hours to warm the unit and this is adjustable. With the running cost of £1 per month I'm more then happy and the humidity in the bungalow sits between 47 and 55% now, where before it was around 70% plus.

[@CharlieDIYte]

You and so many others have been delighted with their PIVs. Thanks for sharing. Is yours Nuaire or Vent Axia?

[@hannahswann747]

Thank you so much for this incredibly helpful and informative video. I’m renovating an old stone house in Wales with soaking wet cellar walls even after removing the cement render 8 months ago. Your advice on HRV systems was a eureka moment as I didn’t know they existed so many thanks for that! 👍

[@thejaxter6384]

De-mistify! Perfect unintended pun!!!😊 we struggle a bit in our old cottage. We have underloor heating in our bathrooms. As soon as the outdoor temp falls below 12 degrees the underfloor heating is set at 18 degrees 24 hours a day. This means that the rooms are kept at a level temperature and it prevents the room from forming condensation on the outside wall. We have double glazing but we put up pvc sheets attached with magnetic tape to the wooden frames and very little condensation forms. We also have a dehumidifier upstairs which we keep running 24 hours a day. In colder weather, I iron in front of the hob and turn on the extractor to pull the steam out. We have a tumble drier which drains the water directly into the same pipe the washing machine empties into. We keep furniture away from outside walls. We have a huge fitted wardrobe in a bedroom, it is mostly against an outside wall. It is lined with polystyrene and it isn't packed out. We leave the doors, and base drawers, open a couple of inches to encourage airflow. It has taken us about 20 years to get to the point where we have no damp corners and no mould.

[@CharlieDIYte]

Everything you've done there is spot on - as discussed in this update.kzbin.info/www/bejne/hJPXmp1-gN5ljNEsi=P-JkGxJlrq0czvg8 I just wish more people could take this approach.

[@heriothandyman3148]

Well done on going the extra mile, fantastic data collection and analysis. We moved into a property with a Heat recovery system, not knowing anything about it. 2 years on, very very thankful for it.

[@JasonPMartin]

I had a PIV unit installed last year. It’s stopped condensation on the windows but doesn’t appear to have improved the overall air quality that much. It’s supposed to get into every corner of the house but there are blatantly blind spots where the air won’t reach, namely the bedroom. In all I don’t think it’s worth the £1k price tag I paid. I’ve now installed powerful extractor fans in kitchen and bathroom and this has made a big difference. I’ve even put a silent one in the bedroom as the bad air affects my sleep. Other things that help are slightly cracking windows and venting bricked up chimney breasts. It can be a total mission sorting indoor air but these steps seem to have cured it. We’ll see how it goes. I’m at the end of my tether. If this doesn’t work I’m moving house!

[@GosforthHandyman]

Charlie - that's some serious work you've put in to that video! Awesome stuff! Fantastic video as usual. We're in a new build at the mo. and the total lack of any form of damp or condensation has been a nice change. In fact we sometimes get condensation on the outside of windows! Wouldn't surprise me in the rel. humidity was

[@chrispybus8741]

£

[@monevaluation4716]

Extremely useful video. Thank you. Only thing I'd add is when you cover the sciency bits, talk a bit more slowly please so I can process what you are saying before the next chunk of information. I've taken to draining boiled veg outside in the garden to avoid all that steam mixing with the indoor air in the kitchen. I always open window wide whilst showing. Open bedroom window in the morning, even if it's cold outside. Living in a 1870s house, some doors have gaps under them. Ive realised those gaps are my friends and not to get rid of them! Thank you again for your very good videos.

[@deftouch]

This was a fantastic video Charlie, and so informative and interesting that I wouldn't have minded if it went on another 25 minutes. Love your videos, thanks a million.

[@CharlieDIYte]

Thanks David, I really appreciate that, and it's quite timely as I'm working on a smart heating install right now and in spite of my best efforts it's 23 minutes long already with another 5 minutes to go...

[@Viewer765]

@@CharlieDIYte how long did smart mode on your dehumidifier run for the first time before it started shutting off mine seems to run constantly and when do you have your running for

[@InspiredByBrad]

Cling / shrink film can seal the glass from the air just like dual pane glass, and stop condensation and increase thermal efficiency. Easily applied and removed each season.

[@pavel9652]

I was thinking about it, but I don't think it will stop the condensation, unless it is dedicated product and the condensation isn't too bad.

[@dooovde]

Personally I chose a desiccant dehumidifier since it seems to work better in cold rooms. The amount of water that condensers pull from the air is based on the temp being 30° c. In temps less than 18°, it will put a lot less water from the air. In winter is when I’m going to want to use the dehumidifier and the rooms in my house would get down to around 12° during that period. The desiccant dehumidifier might run at around 350 watts whereas a condenser might run at 200 watts but the extra 150 watts will add heat to your cold room as well so it’s not all bad.

[@goosegog]

What an excellent video! I live in a 70 year old house with cold spots on the walls and persistent mould and damp problems despite having double glazing throughout and being careful to ventilate. I sneeze a lot and after cleaning the mould everywhere I could find it and running two compressor dehumidifiers in my home, I and my house are much better for it. My sneezing has massively reduced.

[@jonbarrie7002]

Hi Charlie, my parents suffered from high levels of condensation and mould growth in their bungalow a number of years ago. They had mould growth on the back of cupboards and cabinets that were against external walls as well as lots of condensation on windows despite them being double glazed. Despite opening widow's, fitting oversized air vents, using a dehumidifier, extractor fans in bathroom and kitchen (both very much over specced for the size of the rooms) incidentally if your fitting ducting to inline extractor fans remember to insulate the pipework or the water vapour could condense in the flexi pipe causing dips, blockages or worse of all a rather large ubend of water which could leak back into the house! Nothing seemed to work. Until after doing serious research i stumbled across the envirovent positive ventilation unit shown on another youtubers channel (fixmyroof) and as you have shown. We purchased one and fitted it in the loft above the hall central to all the rooms as per instructions. Although there is a continuous blow of air which is cooler my parents have not complained about it being too cold. It is slightly cooler so expext that.They leave their internal door in all the rooms open a couple of inches to allow the air to circulate. The results......after only a couple of days condensation gone! After replacing the backs of cupboards etc with new, no mould growth there....fathers breathing better! No more condensation at all. Completely gone! Its now been in for well over 5 years and the unit is going great. Ive just replaced the air filters on the unit (simple and relatively cheap for the time they've been in) Altogether an excellent purchase and highly recommended, provided you can locate the unit centrally and you follow the installation instructions and leave doors ajar etc. I must say along with the oversized ventilation bricks in the walls and the PIV this has fixed their problem and they cannot speak highly enough of it. A good result for them at least. Great video on the subject and as informative as ever. Keep up the good work.

[@CharlieDIYte]

Thanks Jon for that very comprehensive comment. Yes, I'm seriously tempted to install a PIV. I was hoping to get it in, in time for the winter but probably won't have time this year. As you say, you need to leave the doors open, or possibly, as they do in new builds that have internal ventilation systems, leave a 10mm gap under the doors. So satisfying to hear stories like that. You and your paretns must be delighted. I suspect all the earlier work like fitting the air vents will not have been in vain as it will also have helped massively to increase levels of circulation of the PIV - rather like the enhanced effectiveness you get from a kitchen extractor fan when you open a window. Thanks again 👍

[@barnholbol1262]

An excellent video. We're in New Zealand (emigrated 20 years ago from UK), where indoor HVAC is simply archaic; lots of uninsulated, poorly heated houses with single glazed aluminium windows. PIV is available but not compliant with ventilation regs, due to dust, allergens and even asbestos particulates present in roof spaces. Balanced pressure is much better, but requires more air tight building envelopes as well as being expensive.

[@caskwith]

So many videos and forums talk about this subject and get it either totally or mostly wrong. SO refreshing to see a video where somebody gets it right! A few things I would like to mention though if you don't mind. Desiccant dehumidifiers are more efficient at lower temps as you state, if you prefer a cooler house they are the best choice. A compressor type needs a higher temp will be inefficient below 20c, a desiccant will work fine and while it does cost more to run, it puts out heat as a byproduct so you get a bit of free heating at the same time as drying the air. If you can't afford to heat your house to around 20c (we can't) then a desiccant type will be more cost effective in the long run. Trickle vents. I wouldn't bother opening windows or trickle vents. While you are bring in drier air, it is also cold (with some moisture still) so your heating has to work harder and overall costs are increased. Unless your house is very modern and carefully built you will have more than enough gaps and leaks letting in fresh air so I say keep all windows and vents closed and just use the dehumidifier to keep things dry.

[@caskwith]

Oh also PIV units are a complete con and massive waste of money on a house over 20 years old unless you do thorough renovation and air sealing. The money spent will never be recovered in any savings on heating or improvements in humidity. For a new build house built with them in mind they are great but otherwise people are just wasting their money.

[@jackjones3657]

This fact of single pane windows being that much more susceptible to outdoor temperature fluctuations make perfect sense for causing condensation. It's time for me to get double or even triple pane windows! Good video, Thank You!

[@simonclarke6970]

I installed a Nuair Piv unit in a rental property several years ago after regular complaints about saturated windows and mouldy clothes. It is no exaggeration to say that it solved all the problems overnight. Fitted in the loft with the outlet at the top of the stairs. small increase in electricity costs but no complaints from tenants.

[@63phillip]

I am in the UK and I use a desiccant dehumidifier and it works great it lets me keep my place at 50% humidity all winter long.

[@CharlieDIYte]

Glad to hear that. Good work 👍

[@andyandy3506]

Fantastic video, thanks. I've had damp problems from time to time, and had dismissed the idea of bringing in more air from outdoors, as I'd assumed it would be too damp. Completely failed to consider that the lower temperature would reduce its capacity for moisture... A couple of things to add... a very good point about the water vapour from cooking, and I've found a good kitchen extractor fan to be well worth the money spent on it. Probably not worth worrying too much about the kettle though, as despite the noise and visible vapour, an average kettle will only lose a few grams of water when it boils. Insulated plasterboard can be a good way of topping up the overall insulation in a house, but ideally needs a thorough assessment to be undertaken before it's installed. The danger with this stuff is that you're moving the hot/cold boundary away from the surface, so it sits inside the wall itself. So any water in the air can end up condensing on the cold bricks behind the boards, which can be a disaster. Worst case is you get water penetrating from outside (can happen with older non-cavity houses) as well as water vapour coming in from the inside of a house, and this all ends up running down the wall behind the plasterboard. Anyway, thanks again for posting this excellent video. I will definitely be sharing it.

[@andrewhigdon8346]

Relative humidity is a very complex value to predict. Temperature is only part of the problem. For example, winter time can be just as high of relative humidity if not higher than summer time.

[@russelldunning294]

@@andrewhigdon8346 True, it can be raining outside but it can still be fine to open a window to let in the drier(!) air. Winter is the main problem due to cold temperatures leading to condensation and mould.

[@GOLDVIOLINbowofdeath]

I just came across your video after just commenting on other videos on other channels that if the person giving advice does not mention the word dewpoint they have no clue what they’re talking about. I have the advantage of having a degree in architecture although that was over 40 years ago And I never really worked as an architect since I emphasized structural engineering but I still remember this stuff. I am currently converting a sprinter van to be an RV and there’s a lot of controversy about how best to insulate to prevent condensation and or allow the condensation that occurs to escape because vans, unlike most homes, don’t have a permeable exterior surface. And I’m experimenting with a novel solution since I’m not that keen on the solutions that others are using. It’s the rainy winter season in the SF Bay Area so it’s the perfect time to test out new solutions

[@Niknak-noo]

I've had a number of those nuaire (Positive Input Ventilation PIV) units fitted and running for around 15 years. The walls used to drip. The windows used to be covered in damp and the window seals covered in mould. As soon the unit was fitted, the condensation immediately stopped. Didn't even need to wipe the windows in the morning. The original units did not have a heater element. I was happy to put up with the slight chill in the air. The second unit was fitted for free as a warranty replacement (just near the end of the 5 year warranty.) I am on the third unit now. One with the 400W heating element. Have never used the element. It came with a fan controller(wireless) to allow for boost function for use while cooking/ drying clothes etc. A switch for the heater element. Also a wireles. humidistat. There are also numerous settings that can be set from within the PIV unit itself once it is fitted. I wouldn't be without one!

[@CharlieDIYte]

Thanks so much for the comment invaluable! I think I'm going to have to find a way to install one of these at some point. The comments today have been unanimously in favour of them. 👍

[@gekcho]

Hi Furqan, can you tell me which brand of PIV you bought and what part of the world you live in?

[@Niknak-noo]

@@gekcho I live in the UK. The brand was Nuaire Drimaster.

[@leemajor1820]

We had a terrible mould and condensation problem when we moved into the house we still live in today, over 10 years ago. Everything was working against us. A terrible central heating system, no cavities in the walls, aluminium framed windows, lots of large rooms and no internal or external insulation on the walls. The house had recently had all the loft insulation replaced but with all these other issues going on it was a losing battle. And to make matters worse, not long after moving in our 4 year old son developed a cough through the night while sleeping in a room which had mould spores lurking in inconspicuous corners. Something had to be done. We called in a company called envirovent to talk us through the benefits of the positive input ventilation system. After being educated on the reasons why we had mould problems and what we could do to reverse the effects we were advised on installing their system which has 2 room inputs running off of 1 unit. This was because of the size of the house, a regular unit wasnt big enough to tackle the problem. We had the unit fitted and after 2 days we didn't notice any change in the condensation levels and the humidity levels were still sky high. We contacted envirovent and they advised us to switch the unit from the high setting and put it onto boost (maximum setting). 48 hours later we were seeing dry windows for the first time since moving into the house and humidity levels were coming down.... alot! And my sons cough disappeared. Heating bill's reduced due to not warming up all the moisture in the air. This thing was the best investment we made all them years ago. 10 years on, we have upgraded doors, windows, insulated 90% of the walls internally, replaced the central heating system and most of the horrendous radiators that didn't emit any heat but could burn your hand to the touch, and recently extended the house and had modern aluminium framed bifold doors and windows fitted. And the envirovent unit has quite happily sat in the loft for 10 years without so much as a hint of an issue. I have to add, due to all the work we have had done to improve the house and living conditions I have been able to reduce the setting on the envirovent unit to large house setting without any return of any condensation. Something that was an impossibility all those years ago! Conclusion- money well spent and you can't put a price on your families health.