Last time I read the specification there was two methods for sealing DG wood windows.jfc wrote:My point is if the gap is filled with mastic there will be no moisture . As for equalizing air pressure , its a window not a space ship ;D
The two methods that compiled with British Standards:
1. leave a gap all around the sealed unit and frame of at least 3mm and drill drain holes in the bottom rail of the sash to allow any moisture to drain out.
2. Completely fill the the void between the double glazed unit and wood sash with the correct sealant so no water can ingress between the two.
I can't remember just which method but only one of the above is recommended for site fitting.
The sash should be sealed on both sides (internal and external and a bead of propriety sealant used to seal around the sash and double glazed unit on completion.
A lot of failures have been attributed to moisture between the frame and sealed unit breaking down the joint separating the glass unit. Some failures have occurred due to incorrect sealant being used which has broken down the seal in the DG unit.
It's all info obtainable on the net.And I just realised there was a few more posts after your comment Jase making the above obsolete
Nice job Jason