Reply With QuoteWould need a little bit more info tbh - single or double skin construction? Single or double storey? Pitched or flat roof? Etc etc
Anyone know the best way to insulate a
Brick built extension which in the winter months is so cold as to be unusable ?
Built in the 1920s, its single storey with pitched roof, rock wool insulated ,three exterior walls, pebbled dashed. It does not appear to have cavity walls although is a double layer of bricks and they are very cold to the touch - so is the best method to line interior with some kind of insulating board ?
Thanks in advance for yr advice
Last edited by eddie1; 19th January 2024 at 21:30.
Would need a little bit more info tbh - single or double skin construction? Single or double storey? Pitched or flat roof? Etc etc
Timber stud wall with cavity with 90mm Celotx insulation
Double skin pitched roof rock wool insulated
Just my unprofessional thoughts
Check the brick patttern on the outside will give you an indication of a possible of cavities
If your seeing 1/2 bricks it’s probably a ‘single skin’ (not single brick)You’ll need a breathable vapour barrier between the wall and any insulation so and moisture doesn’t get trapped
If you timberstud and cellotex consider a 20mm (or more) layer of cellotex affixed horizontally ontop of the studs to prevent cold spots
As stated above, be prepared to lose some inner room dimensions and build studding throughout with Kingspan/Celotex insulation between for maximum insulation.
Hi
You may be able to use the above, used in roofs so breathes and provides insulation, over a batten framework on the inside. Not cheap but likely less depth lost internally than celotex.
Maybe consider taking off the render and batten-frame outside, with UPVC cladding, keeping all the work outside the house.......
L-K
Last edited by Low-Key; 19th January 2024 at 22:22.
According to my architect friend, external insulation is better than internal.Originally Posted by Low-Key
Only need to overlap when fixing to rafters
Well, I beg to differ, for the UK and similar climates.....
If the insulation is on the outside it only becomes effective once the inside is heated up, which might take a bit of time and energy.
When you look long into an abyss, the abyss looks long into you.........
Not sure on that one, as by the time the heat has reached that point it's escaped. Internal its reflecting it back in
Will the studwork not transmit cold spots from the external wall?
Not particularly. BC stipulates in these circumstances what I mentioned. Loft conversions etc when direct to rafters is 145m rafer with 90mm Celotex, overlap with 40mm.
If existing plaster is sound then new phenolic plasterboards can be dot and dabbed to the walls- must be paper backed sort. Special care must be taken re air tight ness. "I am air can i get thru there" . Dabs must be continuous along all edges and around sockets and switches, i pack up the sheets from the floor and foam the gap, same at head and put a bead of foam along the vertical joint. Look hard at windows, renew if old, create a thermal break seal with foam all around perimeter before mastic, is floor timber? can you get underneath? get some quilt in, right in, tight in.Gotta stop the air moving round on its way out it just robs the heat out of the room.If there is a cavity, seal it from the room, look in loft get 300mm quilt in if you can, get it tidy and overlapping but dont block vent to above the insulation.
When we were refurbishing our old ashlar stone Victorian terrace we used celotex lined plasterboard (50mm celotex or thereabouts) as we didn't want to lose too much internal space and external insulation wasn't an option. It worked really well and made a massive difference to retained warmth in the house especially in the single skinned rear outrigger.
If external insulation to the walls is an option, I, like Draughtman above, believe it is the best option - in that case any heat that gets absorbed by the brickwork wall can't be transmitted to the outside and so once at ambient temperature contributes to the thermal mass of the house. The drawback of external insulation is that it is more expensive, but you don't loose internal space (or need to redecorate). For the roof, a warm roof solution is probably best, but may not be the cheapest - if the void is accessible 300mm plus of rock wool would be a minimum, bearing in mind the need to maintain eaves ventilation. We have 120mm of celotex in a flat roof on our present house.
It’s better to use foam adhesive than dot/dab, it’s quicker and far easier to use plus you only need 3 fixings per board which is far fewer than dot/dab (can’t remember the regs but its something like 9-12 per board for dot/dab) you must use fixings into masonry as that’s to stop the boards falling off and blocking your exit in case of fire.
You can ignore the regs but if you sell and need a new EPC you need documentary evidence of correct installation and receipts.
I have just done a DIY install of 65mm (72mm inc plasterboard) Kingspan K118 internally on my flat, it’s the best performing insulated plasterboard available, it’s made a massive difference to comfort and fuel bills.
65mm is the sweet spot as you are not losing lots of space but the gains are significant, adding more depth and it’s the law of diminishing returns for each extra cm.
You’re right of course in terms of how quickly the internal space initially heats up, but there’s more to it and I should have expanded my original answer.
Architect friend and I were discussing this in the context of solid (no cavity), precast and uninsulated walls- as it happened one of the famous Amersham sun houses owned by a family member of his. Internal insulation in the form of plasterboard with kingspan or similar backing applied directly to the walls is a certain route to condensation problems and not recommended. I’ve got around this in a large coastal building on the IoM by using a separate insulated stud wall so there’s ventilation, but in those Amersham houses, beautiful as they are, the rooms are tiny already so that solution isn’t viable.
Architect friend’s opinion is that while a building externally insulated takes longer to heat up, the walls will then retain heat better and maintain a comfortable ambient temperature, without the aforementioned condensation risk
As an aside external insulation wasn’t possible on those Amersham properties as they’re listed- in fact they present a real challenge to heat.
Good tip is to never take any advice off an architect they are genuinely clueless about anything other than drawings.
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Celotex is a brand, as is Kingspan. So too are Xtratherm and Recticel.
Recticel offers the best value and Insulation UK will be the cheapest supplier, probably by a massive margin.
Though they probably know as much as random people on here suggesting stuff.
It’s a wonder any architect manages to stay in practice if they are so useless.
I dug into this a little when I renovated my last house (mid-terrace so external insulation wasn't an option). With internal insulation there is a risk of developing interstitial condensation which can cause all sorts of damp and mould problems. The trouble being that it won't happen overnight as the condensation occurs within the wall and so will build up over time. Buy the time you realise there is a problem it is a serious one.
I chatted to people at the Green Building Store about it, I think I paid a bit for their advice, and finally decided against as we didn't have the funds to do a proper job which, in our case, would have included breathable insulation system and lime plaster.
Recent experience of dot and dab has left me very wary of that sort of system too. Most recent example was when I couldn't figure out why one whole wall of my kitchen was Baltic cold. I eventually concluded that, as it was north facing, perhaps that was to be expected. Then I decided to sort the kitchen extract as it didn't have a backdraft damper, when I took the hood off I noted that the 120mm hole for the vent passed through a layer of dot and dab plasterboard on its way through the outside wall. So the void between the plasterboard and original wall was effectively open to the outside. I also saw some research a while back that suggested that the air in the void between dot and bad boards and walls actually aids heat loss because the thermally driven currents aid heat transfer from the hot side to the cold side.
Eh ? they design buildings, that’s their job.
In terms of actual construction they are absolutely clueless.
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Dot and Dab is no good on solid walls. It's designed for cavity build.
The friend I mentioned is very much a “materials and methods” man. Like members of other professions, individual specialisms and areas of expertise and focus can vary.
To be honest I would expect an architect to perhaps have a little more knowledge about insulation than some of the other occupations holding forth on here as usual.
Started out with nothing. Still have most of it left.
That makes sense, thank you. I didn't know that but I wish the previous owner of this house did.
Thanks everyone some very helpful advice here
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