Cavity wall insulation + Thermal Looping.

This is my first post on Boards so hopefully this posting goes okay. Im in the planning and design stage at the moment as site is not confirmed yet.

Regarding cavity insulation reading the dozens of forums for the past few weeks it appears clear that every insulation method has faults.

I had planned on having a cavity. using 150mm of this product from Xtratherm, http://www.cavitytherm.com/CavityTherm2011.pdf .I wanted to go cavity as im not convinced on full fill insulation not conducting water on an exposed site.

1) I know this would not reduce thermal looping fully but should it not help that it almost full cavity.?

2) Will a cavity closer on the top of the wall and window not stop thermal looping anyway ?

3) Its said that if there is a 3mm gap or more between the warm wall and the insulation it renders it useless. But if i used a grout to ensure complete seal to the wall would it not fix this problem ?

4)As 150mm of this product gives a U value of .12 in a block cavity wall, do you think further insulation is needed on the inside wall ?

5)If you were to leave the inner leaf of the external walls bare of insulation and use them as a heat bank for passive solar, would you only do this for walls that were exposed to south facing windows ?

Thanks in advance

BryanF

1. it ain't necessarily so
2. it ain't necessarily so
3. useless? who said this
4. IF it actually gives a 0.12w/m2k U-value then I would say that's adequate.
5. no all the house

a lot of what your asking assumes great detailing/ professional involvement and great builders..

archtech

I'm aware of a dwelling that the cavity is been insulated with the 100mm version of that product. The inner leaf is 225mm wide, which allows the outer leaf be left down so that the insulation can be taped & sealed at cut joints where is not t & g with the outer leaf built up afterwards. having seen the insulation I don't think the wall could successfully be built with 2No 100mm conc leaves.

Speaking with the block layer, the work is considerably slower than the typical cavity insulation installation, however to be fair he is doing a very good job.

I certainly wouldn't consider it, if the builder/blocklayer weren't up to scratch.

archtech

archtech wrote: »

I'm aware of a dwelling that the cavity is been insulated with the 100mm version of that product. The inner leaf is 225mm wide, which allows the outer leaf be left down so that the insulation can be taped & sealed at cut joints where is not t & g with the outer leaf built up afterwards. having seen the insulation I don't think the wall could successfully be built with 2No 100mm conc leaves.

Speaking with the block layer, the work is considerably slower than the typical cavity insulation installation, however to be fair he is doing a very good job.

I certainly wouldn't consider it, if the builder/blocklayer weren't up to scratch.

Thanks for that. Why would it be more difficult as you are still building it against a block wall ?

Would this have to be taped and sealed at all corners ?

Out of curiosity why is the builder building the inner leaf on the flat ? is it for thermal mass ?

BryanF

BryanF wrote: »

1. useless? who said this

Bryan, it came from a discussion on this article
http://www.josephlittlearchitects.com/documents/cavity_wall_paper.pdf

and this one.

http://www.greenbuildingpress.co.uk/product_details.php?category_id=9&item_id=174

BryanF

from the green building one

Harrje, [1986] describes thermal bypass as heat transfer that bypasses the conductive or conductive-radiative heat transfer between two regions. Defined in this manner, convective loops, which can include both air infiltration and wind washing, constitute a form of thermal bypass. In this context it should be recognised that the term thermal bypass is being applied to largely unfamiliar, and often unregulated, heat transfer. Furthermore it is an acknowledgement that air movement can lead to a significant increase in the heat loss when compared to predicted values.

I couldn't find the word 'useless'