Breaking thermal bridge to basement walls — how far down for exterior foam?
Planning to build a brick veneer “pretty good house” with 2×6 studs, blown cellulose, and 2-1/2″ or 3″ rigid foam on the exterior. I understand that I have to be careful with brick veneer being a big thermal bridge to the basement walls, so I am planning rigid foam on the interior of the basement walls which will run all the way up to the floor joists, connecting to cavity insulation between the joists.
I have been studying the brick veneer detail here.. https://www.greenbuildingadvisor.com/sites/default/files/images/Brick%20veneer%20detail%202.preview.png
I see in the detail that the foam drops down past the wall plate all the way down the same distance as the brick. The brick drop includes room for both the brick and the foam.
How far down past the wall plate does the rigid foam need to go? Does it just need to go far enough to break the thermal bridge of the wall plate, or does it need to go all the way down to wherever the brick stops? If the insulation on the inside of the basement wall is breaking the thermal bridge of the brick to the interior, aren’t I only concerned about breaking the thermal bridge of the studs and wall plate?
The reason I ask: I will have one wall of the house (the North East facing wall) that, due to the slop of the land, will be 5 or so feet above grade. It is our desire to bring the brick all the way down to the ground. If I can stop the foam at the bottom of the wall plate, then that is less foam I have to use and less brick drop I have to factor in.