Detail: Fat-Wall Windows

Many superinsulated wall designs are well over 6 inches thick. Most window manufacturers, however, will only provide jamb extensions for up to a 2×6 wall. Moreover, wider extension jambs are prone to damage during shipping and carry all the headaches associated with special-order materials. An alternative is to trim out the window in place. The details described here can be adapted to fit a variety of thick wall styles. They represent a technique used by Neil Carter of Charleston, Maine, who builds very fat walls—sometimes 16 inches thick. Carter specs the highest Rvalue window available. Instead of using a jamb extension, he builds window wells with sides that angle out from the window into the room. He has found this detail to be