Insulating old (1790s ) house - conflicting opinions
Discussion
I have an end terrace house, built around 1790
It was renovated sometime in the 1960s, when new walls were studded out, and gyproc boarded. Essentially created a box within the existing stone walled room.
I think the main reason for this was to make the rooms squarer; the original walls vary from front to back as much as 10"
At that point they didn't add any insulation, which I want to add now to the two external walls (front, and end terrace side)
So.. I have an original wall, then a cavity, and then 1960s plates and studwork, then gyproc. The cavity varies in depth from about 2" to about 12 "
I've had a couple of builders round, and had varying opinions, which roughly split into two camps-
- vapour barrier, then celtotex, then gyproc (i.e. keep moisture in the house)
- no vapour barrier, rockwool, then gyproc (i.e. allow the walls to breathe, and let moisture move through the wall)
Both suggested keeping the existing studwork line.
Any thoughts ?
It was renovated sometime in the 1960s, when new walls were studded out, and gyproc boarded. Essentially created a box within the existing stone walled room.
I think the main reason for this was to make the rooms squarer; the original walls vary from front to back as much as 10"
At that point they didn't add any insulation, which I want to add now to the two external walls (front, and end terrace side)
So.. I have an original wall, then a cavity, and then 1960s plates and studwork, then gyproc. The cavity varies in depth from about 2" to about 12 "
I've had a couple of builders round, and had varying opinions, which roughly split into two camps-
- vapour barrier, then celtotex, then gyproc (i.e. keep moisture in the house)
- no vapour barrier, rockwool, then gyproc (i.e. allow the walls to breathe, and let moisture move through the wall)
Both suggested keeping the existing studwork line.
Any thoughts ?
How I’ve done it in the past is line the walls internally with a rigid insulation (as the celotex example below). The only thing I would say is that the vapour barrier should be to the “warm” side of the insulation - I.e between the insulation and plasterboard, not between the “cavity” and insulation - you could run into issues with interstitial condensation issues.
As above, VCL should be warm side of insulation to stop condensation when warm air hits the solid wall surface.
Have you thought about using insulated plasterboard with integral VCL?
https://www.kingspan.com/gb/en-gb/products/insulat...
Have you thought about using insulated plasterboard with integral VCL?
https://www.kingspan.com/gb/en-gb/products/insulat...
Jumpy Guy said:
Thanks, so foil backed celotex sheet insulation ( foil on room side ) and then foil backed gyroc ?
That was another suggested route ..
I wouldnt need separate vapour barrier then ?
I did that on a couple of walls and it’s been ok. That was another suggested route ..
I wouldnt need separate vapour barrier then ?
But the best result I’ve had is with insulated plasterboard (as above) dot and dabbed onto the masonry wall or fixed to battens. They’ve really lifted the temperature of the room.
I used insulated plasterboard on a outside bedroom wall, I used low expansion foam to attach it making sure there was a bead across the top and bottom to avoid any draughts behind the boards ,we have that problem with dot and dab boards in the
kitchen
I also did the same in our under kitchen garden room, cavity block walls with rockwool in the cavity, same system used down there it`s a 6x4 mtr space ,even in winter with no heating it`s never cold
kitchen
I also did the same in our under kitchen garden room, cavity block walls with rockwool in the cavity, same system used down there it`s a 6x4 mtr space ,even in winter with no heating it`s never cold
Jumpy Guy said:
Ok, so just insulated plasterboard ? Onto the studs?
And did you have celotex behind too? And vapour barrier ?
And apologies for the 20 questions; every time I ask, I get a slightly different answer, which is great, but leads to more questions..
Insulated plasterboard onto brick, nothing else no vapor barrier 1930's lime morter brick wallsAnd did you have celotex behind too? And vapour barrier ?
And apologies for the 20 questions; every time I ask, I get a slightly different answer, which is great, but leads to more questions..
You’ll probably get a mix of answers here just to confuse you more!
I’m renovating an old stone cottage in Scotland just now and, like yours, it had renovation work in the late 60s to add a wooden framework internally. I was advised to try to keep everything away from the old stone walls which did involve rebuilding some wooden framework which had touched the walls but was a bit rotten anyway.
We used Recticel PIR insulation in the wooden framework, it comes in different depths which is useful if you have framework that isn’t today’s standard size. This was then covered with foil backed plasterboard.
The cottage spent half last Winter unheated so I was a bit wary once I got the heating system in place. Happy to say with heating on there has been no issues with condensation and the cottage is super cosy.
Best of luck.
I’m renovating an old stone cottage in Scotland just now and, like yours, it had renovation work in the late 60s to add a wooden framework internally. I was advised to try to keep everything away from the old stone walls which did involve rebuilding some wooden framework which had touched the walls but was a bit rotten anyway.
We used Recticel PIR insulation in the wooden framework, it comes in different depths which is useful if you have framework that isn’t today’s standard size. This was then covered with foil backed plasterboard.
The cottage spent half last Winter unheated so I was a bit wary once I got the heating system in place. Happy to say with heating on there has been no issues with condensation and the cottage is super cosy.
Best of luck.
Catz said:
You’ll probably get a mix of answers here just to confuse you more!
...and the reason for that is that there simply isn't a 'good' option.Old stone-built properties worked (more or less...) in period because:
a) the envelope was massively more draughty than we would dream of tolerating these days, which dispersed most of the internal moisture from cooking and respiration before it caused a problem (and people were having a bath once a week, instead of showers every day, so they were generating massively less internal moisture, too) and;
b) there was a constant battle going on between external damp trying to force its way in, vs. heating of the thermal mass of the walls driving it back out. So long as you kept the external walls heated, by living in the place, the 'dew point' within the wall structure would be far enough toward the outside that it was fine.That's why if you leave such a property unlived in and unheated for any period of time, it deteriorates very quickly - the damp penetration wins and finds its way all the way through the walls to internal finishes and timbers.
If you add internal insulation in any shape or form, you move the dewpoint much further in toward the internal face of the masonry wall, which is never a good thing.
You then have a choice between the 'breathable' route (which forces the higher moisture load of modern living into a wall that you've just made more vulnerable by relocating its dewpoint further in), or the 'vapour control layer' route (which forces the vapour toward the next bunch of weak points and cold bridges). EIther way is not good.
MVHR or PIV can help, by dispersing some of the internal moisture before it gets anywhere near the bits of the thermal envelope where it could cause interstitial or surface condensation, but it's a bit of a sticking plaster job.
TL:DR version: there isn't an ideal solution, because solid wall construction is basically a bit crap.
This is all useful, if confusing.
One thing i should add; this is ground floor, and there are various air bricks into the void under the floorboards.
I live on the edge of a moor, with europes largest wind farm, so normally it's pretty windy.
As a result, under the floorboards , and the void behind the 1960s stud work has a whistling gale whenever I've investigated.
One thing i should add; this is ground floor, and there are various air bricks into the void under the floorboards.
I live on the edge of a moor, with europes largest wind farm, so normally it's pretty windy.
As a result, under the floorboards , and the void behind the 1960s stud work has a whistling gale whenever I've investigated.
Olivera said:
Isn't the best solution arguably to do nothing, ergo leaving the original construction unchanged and accepting higher heating costs?
It's one solution, certainly.But few people are willing to swallow either the fuel bills or the discomfort that would incur (remember that when new, apart from heating, people would wear extra layers of clothing, housecoats etc., to keep warm from the draughts - not many people prepared to do that, these days).
The best solution would be to demolish and replace with housing that is fit for modern purpose, but we're too obsessed with nostalgia for most people to accept that.
LaurasOtherHalf said:
Someone's jaded this Saturday eve!
Not really. It's just building science: it's simply not possible to upgrade the basic envelope of these sorts of properties to anywhere close to the standards of thermal efficiency, airtightness and resistance to damp penetration that we'd expect today. It's like driving around in an upgraded Model T Ford... it looks quaint, and you might be able to fit mapped ignition and fuel injection, and hydraulic disc brakes without it detracting too much from the aesthetics, but at the end of the day the fundamental design and structure of the thing just isn't up to snuff by modern standards, and there's nothing you can do about that. You just have to live with the shortcomings for the privilege of everyone (sitting comfortably in their modern SUV's) saying: 'awww... doesn't it look sweet?' as they cruise past you...
Once you realise that, it becomes a simple matter of deciding how much you're willing to compromise, and in which areas. - and everyone's answer to that will be different.
I should add that I'm sitting in a19th Century estate worker's cottage (with uninsulated solid walls) as I type this.
Equus said:
LaurasOtherHalf said:
Someone's jaded this Saturday eve!
Not really. It's just building scienceBut my first thought when I hear it is of all those beautiful, hundreds of years old properties on the continent that retain their original facades in front of modern interiors.
If we can't do it, how can they?
LaurasOtherHalf said:
If we can't do it, how can they?
With the same limitations and compromises to efficiency that we have to accept.There is one significant difference, mind you: we are a maritime climate, with dramatically higher levels of average relative humidity than some European countries (the UK has an average RH of nearly 80%; Germany and Austria, for example, are both about 72%, Hungary 68%).
The 8% difference may not sound much, but in the context of a temperate climate, it's pretty dramatic. The monthly distribution is different, too. Northern France is almost as humid as us (78%) over the year, but only peaks at about 81% in January (coldest month; highest risk), where the UK peaks at 89% at the same time of year. Only the low countries (as you might expect, being pretty soggy) are as bad as us month-on-month.
We actually have software that makes allowance for the differences to monthly average RH even just for variations across the UK when calculating condensation risk, and I can tell you from occasionally having failed to reset the default location that even that makes a difference to whether some solutions will work or not.
Hence if you're talking about Europe as a whole, our buildings are much more sensitive to condensation risk.
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