Thermal bridging at overhangs
I have seen this question asked, but never answered.
We are designing a house in climate zone 4A, North Carolina mountain area, and need at least 3 feet of roof overhang. This is necessary to keep the summer rains off the open windows, and to provide shading. The roof will be an unvented shed type, ceiling at the bottom of the rafters, about 4/12 pitch, with exterior foam board wrapping the whole house.
So the question is, how big a deal is the thermal bridging caused by say a 2×6, scabbed on to the interior of a larger rafter and extending out 3 feet? All well air sealed and insulated at the building envelope.