I’ve written about attention to detail regarding insulation and draft-proofing in previous posts. Today’s topic is a lesser-known factor in building performance but no less important. Thermal bridging. And attention to detail is key here as well.
This diagram does a great job of illustrating the cumulative effect of thermal bridging. Since wooden (or steel) framing has a much lower r-value than insulation, heat can flow (escape) through the studs and dwangs more quickly. In the example above, the framing makes up 1/4 of the total wall space where there is zero insulation. Since heat tends to rise, the problem of thermal bridging is even worse for ceiling insulation.
In other words, the r-value above your head is not simply the r-value as shown on the bag of insulation. If you have thermal bridging, then your r-value is lower.
We are dealing to this by using a suggestion from Ian Mayes, the Eco-Design Adviser for Hamilton City Council. (I reckon this is about the best use of rate-payers money there ever was or will be.) Ian suggests laying the batts perpendicular to the joists and covering them completely.
Even a small layer of insulation will break the thermal bridge enough to save energy. This is what we’ve also done in the bathroom behind our home-made medicine cabinet (future post). You can see the black building paper directly in contact with the exterior cladding. Brrr.
Voila! Eco, thrifty, attractive.
Peace in the Middle East (but keep the oil price high), Estwing