# Sealing between windows and cavity wall



## Squidge (25 Feb 2010)

Has anyone any suggestions for sealing between windows and cavity block wall in a new build.  Expandable foam and tape have been suggested. If anyone has used either/both could you recommend a particular brand and if possible give an indication of costs involved. Thanks.


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## DBK100 (25 Feb 2010)

The two main issues are Thermal Bridging & Airtightness. 
Take a look at the Acceptable Construction Details.

http://www.environ.ie/en/TGD/

They are towards the bottom of the page. 
Proprietary insulated cavity closers are available from a number of companies.

DBK100


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## DBK100 (25 Feb 2010)

Squidge said:


> ...and cavity block wall in a new build.



I just re-read your post.
CAVITY BLOCK!!??  New Build House??
One word:  DON'T!

Have a read of some of the research documents on this website:
http://www.josephlittlearchitects.com/papers.html

_"The Irish hollow block, due to its material and its shape, is representative of the poorest performing hollow blocks being manufactured in Europe today. A different geometry where there are, for instance, many medium-sized staggered slotted cavities, or better still hundreds of small slotted or pencil-shaped cavities, will give a higher Thermal Resistance for the same total void area. This is because the route around the many small cavities becomes longer and longer forcing a greater portion of heat to travel through the voids._"  

_"we advise that the use of Irish hollow blocks as currentlydesigned
for purposes other than sheds or the inner leaf of cavity walls should cease._" Joseph Little Architects.

DBK100


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## seantheman (25 Feb 2010)

Any good?
[broken link removed]


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## Squidge (26 Feb 2010)

Thanks to you both for the links.  Will have a look at the websites.  It's actually cavity walls as opposed to cavity block so sorry about the confusion on that.


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## Sconhome (26 Feb 2010)

hollow block and cavity wall often confused but never the same.

@BDK100. It is interesting that the article stresses that:

"_the use of Irish hollow blocks as *currently designed*
for purposes other than sheds or the inner leaf of cavity walls should cease_"

My bold! There is an acceptable design use where the use of hollow blocks is exceeding the performance of cavity wall construction. Increasingly hollow block is being specified in conjunction with external insulation systems as an alternative to cavity wall construction.

The structure needs to be considered as a complete system with proper consideration given to specific ventilation controls that suit and work to achieve airtightness factors.

By hollow blocking you are creating a warm external envelope around a thermally massive structure which will store and radiate heat back into the home rather than diffusing into the garden!

Just to broaden the discussion . . .


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