Do You Know How To Make An Old House Airtight?

[@apleasantchap]

I have worked on a few deep retrofit projects and will aim to share some of my experience. I apologise in advance for the word salad! Mvhr can be difficult to incorporate in an existing building so needs planning at an early stage to keep it efficient and minimise duct runs. Remember that longer runs require the fans to work harder (and therefore louder). If the building layout allows, keeping the unit close to the stairs can allow most of your ducting to be hidden in a drop ceiling in the landings with wall mounted outlets in your rooms. If its a smaller house you can use a decentralised system (I've used the blumartin freeair before) without any ducting. With any MVHR you need to make sure you have adequate air movement between rooms (I prefer either larger gaps at the base of doors or hidden vents at the top of the architrave). These gaps/vents need intumescent strips or some other solution in a fire partition. Ducting through fire partitions can be handled by specialist modules that seal in reaction to fire. With a solid wall IWI, my favourite approach has been a breathable woodfibre insulation with lime plaster as the principal airtightness layer, as this allows moisture pass through but also achieve good airtightness. I would strongly recommend a condensation risk analysis with most IWI (a 3D model such as WUFI as the glazer method isn't really robust enough for this situation). For floors a great option is a thicker t&g osb decking with joints taped. On continent, osb is used internally to timber frame walls a lot in passivhaus and it's a more robust solution for the floor than a vcl membrane. Original boards can be overlaid if you're aiming for an exposed aesthetic. Bonus points for a perimeter tray for services inset and taped in to the osb. Grommets are great but have to be installed properly and cost more than tape (so contractors often try to skip them and use tape instead). Still, they are the best solution for performance. Pro Clima have a fantastic range of products thst covers almost every situation. Highly recommended. Airtightness considerations often pair well with thermal bridge considerations and in both, minimising and eliminating penetration is generally preferable. You can go wild with this so it's important to understand the clients budget vs performance aspirations. Keeping electrical sockets to internal walls is an easy win in this regard, and if you can accommodate service cavities at the ceiling and floor, they make a world of difference. Apologies again for the slightly untamed list of experiences but I hope it's helpful!

[@robinheydon]

We have an MVHR system but it only has a single 'in' or 'out' per room. You place the 'in' in rooms that you live in - living room, bedroom - and you place 'out' in rooms that create wet / bad air - kitchen, bathrooms. The only alteration to our house to accommodate this was adding a small boxed in area for three pipes that goes to the living room (two 'in' pipes because it is large, and one 'out' pipe in the downstairs WC). 1980's solid brick walls / two story. Installed by Solarcrest in Macclesfield.

[@lazygardens]

Yes - we have a MVHR plan for this house (Montana, USA, VERY cold, low humidity) that involves putting fresh air inputs into rooms on one side and the outlet collectors at the other end. It won't be as effective as a new build and fully piped, but it's better than nothing. The house is "air tight" which means STALE AIR. Double pane windows, gaps caulked, piles of insulation in the attic ... needs air changes.

[@ooslum]

I understand the subject of your video is airtightness but im pretty certain that your research has pointed to the fact that this will only work in a very limited number of properties that by their very location make their completed value worth the cost and effort to implement such a process. Given this, its ironic that the purchasers of these buildings would probably be the most able to withstand virtually any cost of heating. What i dont know, and you may well do,😂 is how this process would compare in price to something like throwing solar and batteries at the properties to reduce energy costs to a similar level. On a practical level a more average home owner would benefit more from the saving without the retrofit to Passive House levels of air control. Ultimately it doesnt matter what we say if someone dictates what is to be done but building 5 million Passive House's in 5 years will be fun to watch. Cheers

[@lazygardens]

It doesn't have to be a huge project. You retrofit where and what you can, because each bit helps. I had a huge Victorian in Norfolk Virginia. Insulation was sparse because the top level was an apartment. The biggest improvement in comfort and energy savings for all the apartments was installing "storm windows" (expensive!) and filling drafts all around the old ones, caulking gaps around skirting boards, and weather-stripping the doors. No walls were opened. In several small houses the target was attic insulation (blown in fiberglass chunks), caulking gaps, and making storm windows of plastic greenhouse covering. Maybe $1000 per house. Comfort level increased, utilities decreased.

[@ooslum]

@@lazygardens I totally agree but there are those that renovate to a high level that an architect will be used, They hose that would use Pinterest and then the remainder that either don't or can't. The purchase price of 4kw of solar and a battery could get in at a very reasonable cost with no fears of condensation damp or mould etc. My guess is retrofitting energy saving measures when no other upgrading is planned and to a level that save 6000 KW/h of energy is fat more that a solar fit under those circumstances but perhaps I am wrong. Cheers.

[@nicholaswaring8393]

We dont want airtight homes. We want our homes to breathe . Seal gaps of course ; ventilate and control draughts.

[@alanfoulkes9383]

Not used them but I have seen a lot about Aerobarrier who suggest they can help with achieving airtightness. Feedback in the UK is limited, but seems to have been successful in the USA?

[@RealLifeArchitecture]

Thanks, I saw a video on this but I don’t understand how it works. They seem to spray a vapour throughout the house and it congeals in the gaps? I could be wrong.

[@alanfoulkes9383]

I did get a quote of about 2k for a 60s 135sqm bungalow I am extending. Their comments were In terms of improving airtightness scores, we certainly can help - in these situations, we often see reduction in draughts from 40-70%, which certainly helps to make all your other improvements work at their maximum potential! To provide a quotation, we just require the location of the project, gross internal floor area and how ‘involved’ the retrofit in the project will be? The ideal time for an AeroBarrier installation is at a dry shell stage, just after first fix (once all external penetrations have been made) - post screed but pre plaster usually. I would be very interested if anyone has hands on experience.

[@lazygardens]

@@RealLifeArchitecture I've seen this: It uses microscopic particles carried by airflow into the leaks, and they (chemically) collect like sticky dust and cure in the gaps. AeroSeal is for ducts, AeroBarrier is used for sealing the building envelope. Needless to say, it's best used on new construction.

[@robinheydon]

Aero Barrier has been used successfully on old buildings too. kzbin.info/www/bejne/eYeYlp-Jq8amn8Usi=oDeUUz14U4BUK9__

[@andrewriley4204]

I run a family heating business. Prior to installing a new heating system ALL properties should have a Heat Loss Survey undertaken prior. As a professional business we undertake these. However, we are possibly in the minority ! The best software for this is by a former heating engineer and called 'Heat Engineer'. Related to this, we refer to the core building and use the phrase:- 'Fabric First'. This simply means that before you fit any type of heating system, the building Fabric is key to the success and failure of the end result. Put simply, if for example, you have new double glazing throughout and 150mm loft insulation and 100mm under the Ground floor, your heat loss will be minimal and you won't need much to get a property to 20⁰c. However, reverse this and you're peeing in the wind ! So:- "Fabric First" 🤩 Hope this makes sense 🙂

[@RealLifeArchitecture]

Yes, I have encountered fabric first and agree it makes sense

[@lazygardens]

Getting a new HVAC system in New Mexico, and the estimator made it VERY CLEAR that his sizing was 100% dependent on upgrading the insulation ... the building inspector's first words were "You need more insulation in the attic!"

[@EnigmaticRealms1]

Aerogel insulating plaster seems malleable and thin

[@RealLifeArchitecture]

I know what that is but haven’t used it. I suspect it requires skilled trades to apply and takes time to dry out. Plus a flexible membrane or spray on vapour barrier will cover joist penetrations.

[@carlb401]

I haven't done it but i had read a few articles on a Victorian semi detached houses that where converted to passive house standards, however the cost is prohibitive for most people. If i remember correctly it cost over £1 million to convert both houses.

[@RealLifeArchitecture]

Good grief! I don’t care how high the gas bill is, it’s not worth it.

[@carlb401]

@@RealLifeArchitecture I just googled it again and it's on Zetland road in Manchester. It cost £1.75 million to buy the houses/ land and convert them to enerPHit plus certification. The details are on the Passivhaus trust website.

[@YodhrinsForge]

Interesting, I live in Edinburgh and have been reading up on the subject from two perspectives - my current Victorian tenement flat which I initially considered renovating but instead intend to sell, and the cheaper small home I intend to buy to retrofit which will probably be a ~60's/70's era (hopefully end-)terraced blockwork cavity wall - and unfortunately after almost a year of digging I've come to pretty much the same conclusion as yourself: it's messy, convoluted, probably requires bespoke approaches on a property by property basis, and if someone is serious is going to need a back-to-brick level deep retrofit. I will say I'm wary of sprayable/paintable or wrap-based airtightness products because unlike more traditional materials or external solutions which from what I can tell will tend to experience point-failures that can easily be repaired, synthetic airtightness layers that are buried in walls will likely fail universally albeit slowly over time and will be much harder to fix; a house that is airtight now may leak like a sieve in 50 years which may not bother the person doing the retrofit for their own comfort, but kind of makes a mockery of the idea of retrofitting for sustainability. When I was considering the flat, I had settled on using membranes only in the floor and ceiling and then only the loose kind designed to be stapled to joists/rafters and then taped, for the walls I decided using a thick layer of Claytec clay plaster applied straight to the stonework(you can get special primer stuff that will let it stick to the floor/ceiling tapes for continuity) with rigid woodfibre boards embedded directly into it was the best approach giving airtightness(providing the clay is thick enough and continuious) while preserving the ability of the building to respire. Airtightness specifically didn't seem an objective, but Laura Kampf's series about renovating an old house in Germany(it's mostly in English) has a lot of interesting information about dealing with "heritage" malarkey, and I think illustrates that for such properties the reasonable objective is probably to *improve* airtightness just enough for superinsulation to make sense, rather than actually achieve it. Frankly one of the biggest problems with older properties especially up here are the windows, especially in the context of all the Cockburn Society/council nonsense peddled around this city; the thing that made me change my approach entire and decide to sell was the fact my flat is *just* within a conservation area and as such *must* have wood framed, rope & pulley sash windows that preserve the current pane layout, which A; can't be made even slightly airtight no matter what you do, and B; would have cost nearly 35 grand to be replaced with double/triple glazed units which would have had minimal benefit anyway thanks to the leakyness. My current plan is almost the exact opposite and my only concession to ecology other than the overall goal of an airtight superinsulated low-energy home is to minimise concrete use to the footings & blockwork for an engineered timber-built extension's foundation. I intend to use one of the "systems" where external, impermeable synthetic insulation will be applied directly to the blockwork/harl(if it won't come off) using adhesive render, with an additional layer of that same render with embedded meshing on top, and a final topcoat of finer silicone paint-based render material, with additional below-grade rated insulation dug down as deep as possible lining the outside of the foundation(with allowances made so as to not bridge the DPC). That outer shell, properly connected to the roof membrane, will provide airtighteness, weatherproofing, and moisture control, and can be refreshed easily with a simple application of exterior silicone paint every 10-15 years. The roof will get exterior insulation, watertight/airtight membrane, vertical battens and hopefully a vinyl-dampened metal roof(minimises the rise in profile compared to cross-battening for tile/slate, also easy to DIY repair), plus internal insulation between the rafters. Cavities will be filled with blown in EPS bead. Rather than faff around, and since both the external and internal leafs will be insulated from the exterior, I'll also seal the floor vents, top the joists with fire-rated ply boards for a subfloor, and also fill the floor void with blown in EPS bead(with superinsulation there shouldn't be any cold spots on the inner leaf to create condensation, the exterior shell doesn't allow moisture to penetrate from the outside, and the properties of the beads plus the higher vapour pressure within the dwelling space as opposed to below it should force any moisture from within the house - which should be minimal thanks to MVHR - to migrate down into the soil rather than hanging around to rot the timbers). A highly vapour-open insulated/acoustic wall on the internal side of the party wall, triple glazing etc and it should get somewhere close to EnerPHit without costing a fortune. That said, that's my plan as a layman after watching and reading probably too much information on the subject and has yet to survive contact with an architect, hah.

[@janwillem6953]

Very interesting Neil. I retrofitted an airtight suspended floor shown ecological building solutions in your video. I am set to use an air tightness paint in the attic over the next few weeks ( my approach may be a first on this), most ceiling air tightness applies a membrane and then adds an additional plasterboard. Blower door test follows that. Cambridge carbon footprint has a webinar you might want to look at on air tightness.

[@johnfreshwater3790]

The best person to watch regarding old properties is Peter Ward. Heritage House. My house is 220 years old and I have done everything possible to improve it within my budget and now heat it with an ASHP. Which all my friends said wasn't possible

[@RealLifeArchitecture]

I have been watching Peter Ward and he speaks a lot of good sense with respect to damp

[@aknorth1053]

the purpose of tight construction is to control the air changes that occur. By passing them over an erv/hrv you recover the energy you put into heating /cooling the air. combined with copious insulation you require very little energy to heat. Think of a thermos with the lid on vs a paper coffee cup with a bunch of holes in it

[@RealLifeArchitecture]

I understand the concept but I suspect this is much easier to control in a new build than when retrofitting an older property.

[@tcroall]

No all rooms need and intake and extract when using an MVHR - depends on layout.

[@RealLifeArchitecture]

Thank you, I didn’t know that. For house sized projects in the UK are there M&E firms who can provide design guidance?

[@tcroall]

Yes there are. This independant advice is especially helpful if you are also installing a heat pump. Most installers don’t consider the internal of MVHR and heat pumps - really needs a whole system view to get it right. I’ve messaged you on your website. Reach out and happy to give you more info.

[@ianbird4737]

Surely the focus should be on minimising heat losses. Yes, stopping draughts is part of this but I don't want a sealed home. I have trickle vents in all my windows which are left open all year round. A couple which are in locations where the wind strongly swirls around under certain conditions may be closed when it is very windy when there is a noticable air flow coming into the house. I don't suffer from closed rooms smelly musty, nor do I have any instances of mould in the bathroom or kitchen. One thing that (subjectively at least) did seem to make a difference to the warmth of the house was applying a waterseal coating to the exterior walls (solid double brick). My thinking was that this would reduce evaporative cooling of the walls particularly in the winter when the weather is generally wetter. A quick, cheap and (unless the sunlight and viewing angle are just right) invisible upgrade.

[@RealLifeArchitecture]

Like most people, I haven’t lived in a Passivhaus and I am skeptical that sealing our homes will work in the real world. Interesting that a water seal coating appeared to improve the warmth.

[@Red_King_88]

Thinking about it, a water seal coating the wall leading to increased warmth makes sense as a wet wall will be more expensive to heat. I can’t render / clad the exterior of my property so im interested in applying a similar coating.

[@Red_King_88]

I agree that nobody should want a sealed home. A draught is uncontrolled ventilation, whereas your example of closing and opening trickle vents is controlled ventilation. MVHR systems allow fresh air in too.

[@danrooke7372]

I'm not far off moving into a property I bought with the intention of reducing grid consumption to a minimum. My aim is basically to install triple glazing (need to decide on trickle vents or not), install air source heat pump and new hot water cylinder, install MVHR, solar and battery storage. I'll need to look at the fabric and decide the best approach so lots of research to do. There is wall, underfloor and loft insulation from the 70s so I suspect replacing this and sealing up gaps will be a reasonable approach, but I need to ensure I keep moisture out of the timber frame. As you say, building standards need to improve for new builds and good to hear Scotland are making this change. Retrofit is so hard and intrusive in comparison to the extra effort at construction time. It's a no brainer but lots of training needed. More resources to help with retrofits are always welcome so that DIYers can tackle this well informed.

[@Marv968]

@@danrooke7372 if you're definitely installing an MVHR system, then there's no need for trickle vents in your windows. The MVHR well taken care of the ventilation

[@HowardBurgess]

Air tightness is important, but it’s worth remembering the obvious: if there’s no wind on a particular day then it doesn’t matter how airtight your home is. (Ignoring for a moment the stack effect of heated air rising.) So, in a usually calm urban setting down south, a leakier building won’t be the end of the world. However, in a windswept country location, you’ll reap the rewards of airtightness work.

[@lazygardens]

Do you do much with wind breaks?