Does anyone have experience with CorkSol for insulation and air tightening?

I’ve just bought the world’s draftiest house with U values for the exterior walls of 1.5 or so. Supposedly 6mm of CorkSol will cut 0.5 off that U value (source is one of their case studies) and I’m wondering if anyone has any experience with this. It is solid walled so can’t just fill the cavities for a quick win.

Has anyone heard about this stuff, or used it? Is it worth it, and if you’ve had it, what did you pay?

CorkSol appears to be similar to Diathonite, which has a long record of application in EnerPHit and Passivhaus Certified retrofits. Whether CorkSol is as good as Diathonite I wouldn’t know.

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As an afterthought, if you fit insulation and/or render to the walls your current windows will become embedded. Far better to replace windows and doors before such a fossilising action.

That is an extremely good point. Really is murderous trying to get things in the right order - I’ve just moved somewhere and am trying to work out what makes sense when and dozens of things keep coming up. Is there a way to not box myself in with that? It seems odd when glazing units only have so much lifetime in them. I suppose the answer is re-render when the units are dead?

Corksol’s claimed lambda value is 0.058W/mk, while googling around Diathonite says 0.045 W/mK. Not really up on my numbers for things like breathability and air tightness though so need to do some more research there I think.

Cheers for the answers by the way. Appreciate being able to chat to people whose eyes won’t glaze over about this…!

Generally a depth of 2cm of wet applied plaster is considered airtight. Vapour permeability is not particularly affected by increasing depth beyond the minimum specified. U-value, of course, improves with depth.

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If possible find an independent source.

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Looking through my records I found this regarding Diathonite:

Diasen is an Italian company which develops and manufactures green building materials such as our cork-based plasters Diathonite, which represent a unique mixture of cork granulates, perlite, clay, cellulose fibers and natural hydraulic lime.

Please, feel free to contact our distributor in the UK for our cork-based materials for technical suggestions and prices:


Carlisle, Cumbria, CA5 6LF

United Kingdom

Tel 01228 711511

There is no real limit to the total thickness for our materials. It is important that each layer is applied with a thickness of 30 mm and that if the total thickness is higher than 50 mm you have to reinforce it by using a fiberglass mesh.
“natural hydraulic lime” helps balance humidity, so long as it isn’t covered with a vapour barrier like vinyl wallpapers or oil/synthetic based paints.


CorkSol being so proprietary I’ve ended up opting for 100mm or so of cork board for EWI and 5mm of breathable render instead. It is, at minimum, easier to source information about!