Thermal bridging occurs wherever assembly components with low R-values relative to surrounding materials span from the inside to the outside of a building assembly.
What's the UK doing about energy efficient building, you ask? They have a zero net energy homes initiative, where all new homes in the UK are supposed to be zero net energy by 2016. Probably not going to happen on schedule, according to an article from NewStart magazine, described on the Barefoot & Gilles site. (H/T to Sue Butcher for the link, via Twitter.)
Flaws in the government’s zero-carbon vision have forced ministers back to the drawing board. Is there a realistic way forward?
One wall design that is sure to become more popular utilizes 2×4 studs, 2" foam board as a thermal break, 7/16 OSB or other structural sheeting using 3.5" screws for fasteners. Then the 2×4 stud cavities are sprayed with 2" of closed cell foam. The total wall thickness ends up to be 6-9/16", standard for window and door jambs. The R-Value of this quiet and comfortable energy wall is 24!
There are still questions about the GHG impact of making and spraying the foam, although The Foam Man also points out that all insulation techniques involve tradeoffs, and some spray foams have a high quantity of soy-based content, which lessens their footprint vs. petrochemical-based foams.