From Daizen News, March 2013
The photo below shows a thermal image from a blow door test, superimposed over a shot of the house itself. A blow door test forces air through the house to determine where heat is escaping. The tongue-and-groove decking and, especially, one triangle
along the roof are areas of air leakage. Since they are in the upper part of the house, the heat loss is tremendous.
The air-tight joints with gaskets that we use prove that our joinery is not causing the heat loss. In one spot, where a beam intersects the roof plate via a wood housing, we thought a gasket was not needed. But the photo shows a distinct air leak. What we learned from this test result will change our frame joint details immediately; and with this knowledge, the leak was easy to fix.
More on an air-tight joint.