Granite (stone) house wall insulation

[Daniel C]

As I mentioned in my first post, I will split the tasks which I need to work on.

 

I hope I am posting at the most relevant location, this post would be about insulation of a granite house walls internally.

I have been advised that granite houses should not be insulated directly on the granite, it needs to have a cavity so the granite can breath and dry.

I am wondering what would be the best way to insulate the walls internally while they still keep their breathibility.

 

I come across a product which called Bauwer light, anyone used this before, reviews does not seems to be incredibly conclusive?

Would it worth to go for that type of insulation?

[A_L]

1 hour ago, Daniel C said:

I hope I am posting at the most relevant location, this post would be about insulation of a granite house walls internally.

I have been advised that granite houses should not be insulated directly on the granite, it needs to have a cavity so the granite can breath and dry.

I am wondering what would be the best way to insulate the walls internally while they still keep their breathibility.

 

I come across a product which called Bauwer light, anyone used this before, reviews does not seems to be incredibly conclusive?

 

The cavity will be so that water vapour passing through the insulation can be carried away by air movement before/after condensing on the cold granite

You need to be confident that warm room air cannot bypass the insulation and get to the cavity, this can be difficult with intermediate floor/celings

The idea that granite is breathable is well ............................

Internal insulation in this situation requires an effective vapour control layer (VCL) on the warm side of the insulation and/or an insulation with a significant vapour resistance itself

To achieve e.g. current building regulations you would require at least 300mm of Bauwer light!

 

If I had to I would use PIR/PUR insulation hard onto the granite with a VCL

 

External Wall Insulation is much simpler although I can understand if you want to/have to keep the external appearance in the 'granite city'

[Jeremy Harris]

6 minutes ago, A_L said:

 

To achieve e.g. current building regulations you would require at least 300mm of Bauwer light!

 

I really don't know how companies like this can try and sucker people into thinking they have some sort of "miracle product", that apparently defies the laws of physics.  It seems that no matter what regulations we put in place regarding advertising claims, snake oil salespeople will always find a way around them.  Thankfully, there is a fairly widespread body of knowledge around on forums like this that can go some way towards debunking the use of products like this as supposed insulation.

[Daniel C]

18 minutes ago, A_L said:

To achieve e.g. current building regulations you would require at least 300mm of Bauwer light!

 

10 minutes ago, JSHarris said:

 

I really don't know how companies like this can try and sucker people into thinking they have some sort of "miracle product", that apparently defies the laws of physics.  It seems that no matter what regulations we put in place regarding advertising claims, snake oil salespeople will always find a way around them.  Thankfully, there is a fairly widespread body of knowledge around on forums like this that can go some way towards debunking the use of products like this as supposed insulation.

So no Bauwer, OK

 

20 minutes ago, A_L said:

 

The cavity will be so that water vapour passing through the insulation can be carried away by air movement before/after condensing on the cold granite

You need to be confident that warm room air cannot bypass the insulation and get to the cavity, this can be difficult with intermediate floor/celings

The idea that granite is breathable is well ............................

Internal insulation in this situation requires an effective vapour control layer (VCL) on the warm side of the insulation and/or an insulation with a significant vapour resistance itself

 

If I had to I would use PIR/PUR insulation hard onto the granite with a VCL

 

Is PIR and VCL is the best option?

If yes just a couple of questions:

• How thick PIR boards should I use?
• Does the crawls space insulation effect any decision here?

 

20 minutes ago, A_L said:

External Wall Insulation is much simpler although I can understand if you want to/have to keep the external appearance in the 'granite city'

Yeah, I would like, and maybe even must keep the granite look

[Jeremy Harris]

For under the floor I'd go with 120mm bare minimum PIR thickness, ideally 150mm or so.  It really comes down to how much you're prepared to spend, but if you're doing the labour yourself (which is far and away the most expensive bit) then I'd say that I've never heard anyone complain that they've used too much insulation!  It's one of those "fit and forget" things that keeps paying for itself forever.

[Daniel C]

28 minutes ago, JSHarris said:

For under the floor I'd go with 120mm bare minimum PIR thickness, ideally 150mm or so.  It really comes down to how much you're prepared to spend, but if you're doing the labour yourself (which is far and away the most expensive bit) then I'd say that I've never heard anyone complain that they've used too much insulation!  It's one of those "fit and forget" things that keeps paying for itself forever.

I will do the labour myself, or at least try...

As you suggested in my other thread, I will try to go with minimum 150mm between the floor joists, my question is the thickness for the walls, should that be the same?

[Daniel C]

I went for a walk (gorgeous weather even in Aberdeen) and bumped into a building site where I had a chat with a guy who was doing to walls for a granite house.

He advised the following: granite wall, 10mm gap, 2L2, 10 mm gap, then put mineral wool on the inside and finish with plaster board etc. 

He said insulation boards tend to sweet and they are expensive compared to mineral wool, I am better of spending the difference on 2L2.

 

Any suggestions?

[A_L]

The absolute minimum is a 25mm cavity, with battens to carry insulation and 75mm of PIR (to achieve U=0.3). Mineral wool will be 50% thicker to have the same effect.

I would not use 2L2 on the cold side of the insulation as it is a plastic sheet and when taped at the edges a vapour barrier and in the wrong position. I think 100mm PIR would be reasonable but it may depend on how much floor area you are willing to lose.

[Daniel C]

I was just looking at their brochures and installation guides, It does not seem the best as they state minimum 75mm cavity, then they shaw a drawing for just 60mm... but they install it between brick wall and aerated block (I assume this is serves insulation purpose):

 

I assume I need to seal the cavity from the roof and crawl space ends, am I right?

[Daniel C]

Realised some (probably) leak damage in one of the rooms, removed some of the horse hair plaster thingy and this is how the wall looks like behind it:

There is no insulation at all, I hope there is a wood structure where I can put in some insulation, if there are not any I might need to build one, or go with alternative insulation methods like Lime plaster mixed with hemp directly to the granite wall.

 

What do you guys think about this method, I got this suggested:

Build a stud wall leaving an air gap between the external wall & any insulation. Use rigid rockwool batts, and finish off with a wood wool board

[Daniel C]

So yeah, as I suggested, the walls are built the way like that, I do not know what that technique called. This is how I think I could insulate it:

 

Questions:

• Do you think this is generally viable? 
• On the photo below the nails are rusty, not sure if they require any treatment/replacement?
• 100mm PIR for wall, sounds good enough?
• Thickness suggestion for wallboard/plasterboard
• Thickness suggestions for wall vapour barrier?

 

Update, These are the thickness for the regulation (0.3 Watts / m²K):

• EPS – 88.6mm thick
• Mineral Wool – 108.6mm thick
• PIR board – 65.7mm thick

Edited July 4, 2018 by Daniel C

[scottishjohn]

On 04/07/2018 at 22:30, Daniel C said:

So yeah, as I suggested, the walls are built the way like that, I do not know what that technique called. This is how I think I could insulate it:

 

Questions:

• Do you think this is generally viable? 
• On the photo below the nails are rusty, not sure if they require any treatment/replacement?
• 100mm PIR for wall, sounds good enough?
• Thickness suggestion for wallboard/plasterboard
• Thickness suggestions for wall vapour barrier?

 

Update, These are the thickness for the regulation (0.3 Watts / m²K):

• EPS – 88.6mm thick
• Mineral Wool – 108.6mm thick
• PIR board – 65.7mm thick

I have been looking at a similar built house --some what more delapidated  though .

the suggestion I have been given is to clean interior of granite outer wall and get contractor to  sprayfoam with PUR closed cell type   behind the studs covering all of the outer wall at a thickness of 30mm min

this will totally water proof and separate outer wall from inside of building  --then 100mm min of pir and vpl +plasterboard