Passivhaus Consultant and Designer, Bristol.  Very Low Energy Buildings.  Domestic and non-domestic.  New build and refurbishment. 

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Bristol, UK

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External Wall Insulation - airtightness strategy

Week 5

The boards went up in 2-3 days.  We stuffed rockwoll into the eaves to ensure continuous insulation from the Diffutherm boards into the roof.

Boggest problem was in congested areas around pipes and windows.  In some place the board T&G jpints between the boards were cut off to enable small pieces of board to be fitted in.  The joints were taped with expanding fom tape (Compriband type) between the board and airtightness tape over the junction.

The boards form the air tightnerss layer and the T&G joints in the boards are integral to this, so wherever there is no T&G joint airtightness tape is used over the join.  Wherever possible the aim is to maintain an airtightness layer continuously with the boards, but this hasn't always been practical so I have taped on the render below the boards or internally eg around the new window.

Around services we have used Rissan tape which is flexible to seal the pipe to the underlying render.  We will also stuff the gap between the pipe and board with board fragmentys and tape over with Wigluv tape.  Wherever tape goes onto masonary the surface is primed with Dockskin - a PVA based primer.

We have also taped the window frames to the underlying render.  The tape had to be cut down so it didn't overlap the fares too far.





This window was taped internally due to lack of space externally.  Note taping along the mortar joints.

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