Thickness of new cavity wall

[Perry525]

Year ago, it was quite common for wind blown rain to pour through solid brick walls. The cavity was invented to enable the rain to run down the inside of a poorly built wall (builders always try to use as little mortar as possible - regardless of its effect on the wall and the people living there) and therefore keep the inner wall dry. The problem with this was that in ventilating the cavity the homes insulation was downgraded to that of a single width brick.
Hanging tiles or slates on the outside is more expensive, but is guaranteed to keep a wall dry.

 

[mointainwalker]

@perry

can you back up your claim about Aero gel being 10 times better than polystyrene. i really would like to learn if that is true/

 

[^woody^]

Yes, and also to back up that it's performance does not degrade so that its initial high purchase cost does equate to actual cost savings over the life of the product

ie when is the break-even point compared to traditional insulation?

 

[JamesNorton01]

Aerogel has a conductivity about half of Celotex so you'd need 25mm. But Celotex has a BBA certificate and has been tested to need only a 25mm cavity depending on the exposure of the site. I assume Aerogel hasn't, so ur back to 50mm cavity.

ie. same thickness but more expensive and you get to test their product in situ to see if it works...

J