An Air-Tight Joint
From Daizen News, September 2012
We see two different types of timber frame. One is a frame covered with Structural Insulated Panels (SIP) for high energy efficiency: a highly insulated, air-tight house system.
The other has an infill wall system where the frame is visible both inside and outside. In the infill wall frame, we use full-size tenons so the air cannot penetrate, but we also started using a gasket that is slotted into the joinery and then fills at the frame raising. The HannoWerk seal from Germany is a closed cell seal that expands to block any air or water that might run into the space.
Since we use a seal, the tenon does not need to be full size. We couldn’t achieve this effect with a bead of caulking because timber can shrink and, if a gap occurs, the caulk doesn’t have the ability to expand. Here you can see a groove just to the left of the tenon, where the seal will sit.
The seal in its groove. The groove is necessary so that the seal is seated and is not crushed as it expands.
The groove, with seal, is outside of the joinery. Most likely, the seal will be hidden by a framed infill wall.
Seal arrives to us compressed in a roll that will expand to almost 10 times its original size, to ensure that the gap is sealed.