External Wall Insulation and Ability to Breath


Postby MikeGrahamT21 » Mon Jun 27, 2016 3:55 pm

Hi guys,

I'm trying to find some solid information (a lot of contradictory reports online) of which way to go with EWI in terms of breathability. Some sites, including kingspan suggest breathability is complete rubbish, but is that just because their insulation isn't breathable? Wood fibre manufacturers say its the most important thing!

We are refreshing a 1968 bungalow, which is cavity wall (brick, 70mm filled cavity, block), currently around 0.6U, to around 0.2U by using EWI, and also to refresh the outside appearance with brick slips.

Initially I had planned to do the most common method of EWI, using 100mm EPS, but I'm concerned about water vapour transmission into the structure.

I've ran everything through BuildDeskU and WUFI, and currently as it stands, we already have condensation risk, by applying 100mm EPS this risk goes completely. With Rockwool, the same happens, there is no risk present.

I honestly don't know which way to go, but Rockwool is harder to DIY install, and more expensive, so I'm bending toward the EPS, but I'm getting samples of them both to compare.

Does anyone have any experience with EWI?

Any info greatly received.

Regards
Mike
MikeGrahamT21
Rank: Labourer
Progress to next rank:
75%
Posts: 4
Joined: Mon Jun 27, 2016 3:47 pm

Sponsor

Simply Build It

Postby effingell » Tue Nov 29, 2016 9:16 pm

Ive had very mixed results with external wall insulation , theres no real proof it helps that much especially with all the thermal bridges you get , The rate at which it deteriorates surprises even me, the guarantee you get is valid as long as it has been installed properly which is from the company that installs it so their not confident it will last either.
i think the selling point is you get your house rendered and painted.Its much more effective to insulate internally you only need about 1inch thermal board.Its 10x effective 10x cheaper wont self destruct because its not exposed to the elements .
The whole point of breath ability is not talked about because if it breathes water gets behind the insulation which will cause it to blow. the render. You did say you were doing it yourself though so it would work out cheaper than the companys prices. As they say you pays your money you take your chances.
effingell
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Tue Nov 29, 2016 9:00 pm

Postby Bauwer » Wed Nov 30, 2016 10:01 am

effingell wrote:Ive had very mixed results with external wall insulation , theres no real proof it helps that much especially with all the thermal bridges you get , The rate at which it deteriorates surprises even me, the guarantee you get is valid as long as it has been installed properly which is from the company that installs it so their not confident it will last either.
i think the selling point is you get your house rendered and painted.Its much more effective to insulate internally you only need about 1inch thermal board.Its 10x effective 10x cheaper wont self destruct because its not exposed to the elements .
The whole point of breath ability is not talked about because if it breathes water gets behind the insulation which will cause it to blow. the render. You did say you were doing it yourself though so it would work out cheaper than the companys prices. As they say you pays your money you take your chances.


External insulation is generally always preferred to the internal. The reason behind is that external insulation would keep your walls warm and use them as a heat accumulator, while internal insulation would keep your walls colder. In many cases external insulation is not always possible, for example if you are not allowed and do not want to alter a view of your cottage. In such cases internal insulation is recommended. If your home got a solid stone or solid brick wall, permeable solution need to be considered, possible options:

Image

If your home walls have a cavity, impermeable insulation like EPS, Kingpan, Celotex generally works fine, unless there are humidity and condensation issues already exist. The possible reason could be filled cavities when external brick got minor defects, therefore water from outside could be traveling inside through a filled cavity.

Permeable insulation or renovation render plaster help you home being dry and warm.
Bauwer
Rank: Apprentice
Progress to next rank:
73.7%
Posts: 19
Joined: Mon Aug 22, 2016 2:36 pm

Postby Bauwer » Wed Nov 30, 2016 10:15 am

effingell wrote:Ive had very mixed results with external wall insulation , theres no real proof it helps that much especially with all the thermal bridges you get , The rate at which it deteriorates surprises even me, the guarantee you get is valid as long as it has been installed properly which is from the company that installs it so their not confident it will last either.
i think the selling point is you get your house rendered and painted.Its much more effective to insulate internally you only need about 1inch thermal board.Its 10x effective 10x cheaper wont self destruct because its not exposed to the elements .
The whole point of breath ability is not talked about because if it breathes water gets behind the insulation which will cause it to blow. the render. You did say you were doing it yourself though so it would work out cheaper than the companys prices. As they say you pays your money you take your chances.


Hi Mate,
External insulation as always preferred as keeping your wall warm and using them as a heat accumulator. Unfortunately external insulation is not always possible, for example if you do not want to alter your cottage stone view. If your home traditionally built, eg wall do not have a cavity permeable options need to be considered, for example:

Image

if your home walls got a cavity, more impermeable insulation options could be considered as well, like EPS, Kingspan, Celotex, etc
Bauwer
Rank: Apprentice
Progress to next rank:
73.7%
Posts: 19
Joined: Mon Aug 22, 2016 2:36 pm

Postby effingell » Thu Dec 01, 2016 7:16 pm

Hi appreciate your feedback always welcome .

"External insulation is always preferred to internal insulation" in your opinion
and i would disagree you can use stone walls to accumulate heat , they will absorb heat that's true but they dont release it back into the house because there's polystyrene sheets on the outside it slowly dissipates through the various thermal bridges, there's no need to heat your walls you insulate from them they stay on the cold side. You haven't had to pay to heat the walls .
I notice on your website you sell Bauwer light render for use on external insulation , could you possibly be a little bit biased?
effingell
Rank: Labourer
Progress to next rank:
25%
Posts: 2
Joined: Tue Nov 29, 2016 9:00 pm

Postby Bauwer » Thu Dec 01, 2016 10:16 pm

effingell wrote:Hi appreciate your feedback always welcome .

"External insulation is always preferred to internal insulation" in your opinion
and i would disagree you can use stone walls to accumulate heat , they will absorb heat that's true but they dont release it back into the house because there's polystyrene sheets on the outside it slowly dissipates through the various thermal bridges, there's no need to heat your walls you insulate from them they stay on the cold side. You haven't had to pay to heat the walls .
I notice on your website you sell Bauwer light render for use on external insulation , could you possibly be a little bit biased?


Hi Mate,
Bauwer vapour permeable insulation is applied both ways, internally and externally. So I am not biased this way.
Polystyrene sheets are not permeable to the water vapour and therefore not recommended to use in older, traditionally built breathable houses.

Regards, Alexander
Bauwer
Rank: Apprentice
Progress to next rank:
73.7%
Posts: 19
Joined: Mon Aug 22, 2016 2:36 pm

Display posts from previous
Sort by
Order by



  • DIY How to Project Guides

  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!



 


  • Related Topics