Solid wall insulation

[housepuzzle]

Will you tell me what you think of a type of solid wall insulation which is made of expanded polystyrene with a render on top? The product has a BBA certificate, and can be put on the outside of a solid brick wall. My house is an Edwardian terraced. I do not like the idea of attaching polystyrene to the outside of my house, but maybe it is a better product than I think it is. Please advise me. Thank you.

housepuzzle.

 

[middi]

Attaching insulation to an exterior wall is very common and practical, all in the interest of home comfort and energy saving of course.
Polystyrene is a very good and cheap insulator albeit a very high risk flammable material. If polystyrene is trapped ( sandwiched) between two uncombustible maretials, ie, render and brickwork, it will achieve a good insulation factor. BUT--
When any insulation type is attached to the exterior of a building this will inevitably increase the wall thickness, this will in turn present problems encountered around doors, windows and/or eaves protrusions that need to be overcome. If preserving the aestetic appearance of the exterior building line is of primary concern these openings or protrusions have to be repositioned to keep the status quo. ( this is of extreme importance on listed buildings).
Before embarking on the " polyestyrene" decision for insulation, it is worth noting that the more dense and aluminium foil backed insulation boards available on the market will achieve an isulation factor 3 or 4 times greater than polystyrene for a given thickness, albeit more expensive.
It may be worth for you to make a bit more research as to what would be more suitable in your situation.

Middi

 

[Lime]

I've seen it done recently.
It makes the houses look as though they have been constructed out of lego.
God only knows where moisture in the brickwork goes.

 

[billybuntus]

From personal experience polysterene 'does the job' but the kingspan type products are unbeatable.

We lined an old ground floor north facing bathroom with 1 inch polysterene in our old house (then dry lined it) which made a world of difference to the property.

But that particular room only required a cheap solution to warm steam hitting an icey cold wall and condensing. In our current house we have used 1 inch kingspan on some problem walls and the difference it makes is unbeatable.

I hope to start next year on our north facing exterior wall and line it with 3-4 inch kingspan (or whatever).

 

[tobydog]

All that moisture has nowhere to go but inside.

Repositioning the openings and protrusions, etc, may bring the facade in line but wouldn't the whole house just look plain daft if it's terraced and stuck out from the rest of the row by 2 or 3 inches overall. Anything less and it's probably not worth the hassle. It probably means giving up a proportion of room size but I would prefer the internal options particularly as I'm guessing you would also be giving up the character on the outside.

 

[dans]

All this concern with moisture not being able to escape outside: Am I not correct in saying that if insulated as per Middi's previous recommendations, then the only moisture that will need to escape the brick is the moisture produced from the inside of the building; therefore escaping back inside again?? No moisture will enter from the outside, as the building will be sealed. Both Middi and my structural engineer recommeneded (IIRC) batons, external ply, insulation boards (eg Celetex) with joints ali taped, batons, breathable mebrane, mesh then rendered. This is a fairly common and proven method according to my veryu experienced structural engineer, and one we've chosen to use on our own timber framed farmhouse.

Dan

 

[tobydog]

Doesn't it come down to whether the Edwardian house has an effective DPC? If not, isn't there always a residual moisture in the lower wall that naturally dries to both the inside and outside? The process you refer to is exactly how our new extension was constructed - timber frame but sitting on an exposed brick plinth. Surely that behaves totally differently to a solid Edwardian wall to ground level?. Very interested because I have a solid 9" north facing wall I need to sort. Despite a dpc put in 19 years and 8 months ago (20 year insurance backed warranty!!) it's still saturated in places due to the cement render. Thankfully the damp company concerned is still very active and helpful.

 

[dans]

Which is why we have had to rebuild a brick plinth out of old breathable red bricks. so the render and insulation ends at the plinth.

 

[tobydog]

So with a solid old wall to the ground you would still need a bell drip at the bottom of the new insulation that stops a certain distance from the ground with exposed brick below? Depending on the floor level inside, could this cause a big cold bridge along the lower length of the wall? Sorry but just getting my head clear for when the 'damp' man comes round.

 

[plasticpigeon]

I also live in an Edwardian terrace, and there is no way I would do what you suggest apart perhaps at the back of the house. I don't know how big your house is but mine is only 15 feet wide. The area of the front of the house is dominated by 2 large sashes a front door with a large transom light and a large bay window. I would guess that the area of the facade that is brickwork is around 50% and this is pretty common on this type of house. One of the advantages of terraces is that there are so few external walls. I think on a cost basis, the energy saving would take forever to pay for itself, (it is possible to do this calculation quite simply, but I haven't done it so I cannot say conclusively) and in my opinion external insulation would totally ruin the look of the house and the street. However if your house is like mine there is probably a back addition, which has 2 external walls and as such is affected by outside temperatures much more, and this would benefit more from being well insulated. That is my 2 pence worth anyway.

 

[dans]

Correct, you would need a bell drip as far as I understand it. We have done the same.

I live in a completely detached 16th C farmhouse and the insulation project coincides with a complete renovation, including new doors, windows, roof etc, so changing the profile of the building was not an issue, as I could match everything else into it.

Most of my project is externally insulating a timber frame, but a small section does include Brick walls.

 

[billybuntus]

Good idea regarding the brick plinth. Our house is built of stone. Would it be advisable to insert a horizontal DPC inline with the brick? I couldn't go the full width of the wall but should should be able to manage to cut a horizontal line with a stihl saw in sections?

 

[dans]

I believe, If building in old soft reds then no dpc is required to the new plinth and laid in 1:1:6, with lime mortar pointing above ground level. I would advise talking to your own structural engineer though...

 

[tobydog]

Despite plasticpigeons economic justification for not doing it on the front wall, I would need some convincing to do it at all. We spend countless hours on PPUK justifying the merits of ripping off cement render on the outside of old homes because it allows them to 'breath' properly, so to recommend covering a wall in polystyrene feels totally counter-intuitive.

 

[dans]

That's only because cement lets moisture IN through cracks and then doesn't let it escape. What we're discussing is a completely impermeable barrier that doesn't let moisture IN. The bricks will still breathe internally, only releasing what it absorbs...

I'm no expert of course and can only comment what has been suggested to me by knowledgable people like Middi and a very good structural engineer who has cost me a lot of money!!

 

[plasticpigeon]

I feel like you Toby. I'm certainly not externally insulating any of my house, I like the look of the bricks with their thumb and finger prints all over them and blue brick arches and sills etc, that is why I bought an old house.

 

[Flyfisher]

Apart from the aesthetics (which is in no way intended to diminish their importance!), is it a good or bad thing to have the brickwork structure of the house brought into the heating aspects of the house?

Internal insulation would thermally isolate the brickwork so I'd expect the room temperatures to be raised quite quickly by whatever heating system is used because the brickwork wouldn't have to be heated up as well. For a house that's empty during weekdays while the occupants are out at work, this might be important.

On the other hand, external insulation would thermally include the brickwork within the house, so the heating system would have to also heat up the bricks. For a constantly heated house, the 'storage heater' effect of warm brickwork might be useful, or at least of little significance, but for an irregularly heated house (e.g. empty during workdays) it might be a hindrance in terms of the time taken to heat the rooms.

 

[Lime]

All this concern with moisture not being able to escape outside: Am I not correct in saying that if insulated as per Middi's previous recommendations, then the only moisture that will need to escape the brick is the moisture produced from the inside of the building; therefore escaping back inside again?? No moisture will enter from the outside, as the building will be sealed. Both Middi and my structural engineer recommeneded (IIRC) batons, external ply, insulation boards (eg Celetex) with joints ali taped, batons, breathable mebrane, mesh then rendered. This is a fairly common and proven method according to my veryu experienced structural engineer, and one we've chosen to use on our own timber framed farmhouse.

Dan

The assertions that the building will be sealed from external rain etc is based on what life expectancy?
10, 20, 30 years perhaps?
(Weren't the same claims made for stone cladding?)
"Joints ali taped, batons, breathable mebrane, mesh and rendered" and then fitted to a structure that needs to breath and often moves/settles over time?
I really don't think that is going to work for long, if at all.
I have lived long enough to disbelieve assertions that a building can be sealed for any reasonable length of time, full stop.

Treating older properties in this way is storing up trouble for the future.
One little crack where water can get in and the brickwork will be awash.
Rather like a tiny hole in the bottom of an old wellington boot will soak your sock.

 

[billybuntus]

All this concern with moisture not being able to escape outside: Am I not correct in saying that if insulated as per Middi's previous recommendations, then the only moisture that will need to escape the brick is the moisture produced from the inside of the building; therefore escaping back inside again?? No moisture will enter from the outside, as the building will be sealed. Both Middi and my structural engineer recommeneded (IIRC) batons, external ply, insulation boards (eg Celetex) with joints ali taped, batons, breathable mebrane, mesh then rendered. This is a fairly common and proven method according to my veryu experienced structural engineer, and one we've chosen to use on our own timber framed farmhouse.

Dan

The assertions that the building will be sealed from external rain etc is based on what life expectancy?
10, 20, 30 years perhaps?
(Weren't the same claims made for stone cladding?)
"Joints ali taped, batons, breathable mebrane, mesh and rendered" and then fitted to a structure that needs to breath and often moves/settles over time?
I really don't think that is going to work for long, if at all.
I have lived long enough to disbelieve assertions that a building can be sealed for any reasonable length of time, full stop.

Treating older properties in this way is storing up trouble for the future.
One little crack where water can get in and the brickwork will be awash.
Rather like a tiny hole in the bottom of an old wellington boot will soak your sock.

But what if the fundamental design of the building is flawed? You seem to be describing the protection of some ancient monument rather than just an old house that was badly built onto (like mine).

The only remedy on the rear of my property would be to remove the entire ground and 1st floor walls and rebuild it (ideally). I think we all know this would never happen so the next best step is to make good of the wall.

Providing attention to detail is adhered to (work done to a high standard) why would we have a problem in 30 or 40 years time?

If I do the work I'll guarantee that no water will penetrate. If I thought for a minute that the solution was flawed I would re-engineer it and find an appropriate and robust way around the problem at hand.

If I can stop water soaking into my stone wall for any length of time it can only be a good thing for the building. It currently holds onto water as well as I try and hold onto my wallet.

 

[Lime]

But what if the fundamental design of the building is flawed?

I concede some properties may have design flaws built-in but I think your assertion that an attempt to cover the flaw with a waterproof insulated layer will solve the problem takes a lot of believing.
Questions come to mind such as where is the damp in the wall coming from and where is it going to go eventually.
If you are proved wrong and water does get in, which I think it will, the "improvement" exacerbates the situation considerably.
Meanwhile, even if you are able to construct a completely waterproof layer that lasts 50 years, where is the water in the wall going to go in the interim?