Sal Lombardo is planning a new home in the New York-New Jersey area (Climate Zone 5) and is looking at a long list of high-performance construction options: double-stud walls, structural insulated panels, insulating concrete forms, Larsen trusses, and walls built with light-gauge steel framing.
Wait a minute. Steel framing, as in the stuff that leaks heat through the building envelope like a proverbial sieve? Maybe, Lombardo says, it deserves another look.
“Steel seems like a really good option,” Lombardo writes in a Q&A post at GreenBuildingAdvisor. “Almost unheard of in my area, despite being upwards of 60% recycled, it lasts forever (relatively speaking), is super strong, straight, creates minimal waste, is not affected by termites, pests, or mold, and is equal or close to wood in cost (depending on who you ask).
“I know it has very high thermal conductivity. However, there are configurations that can abate this significantly,” he adds, such as a double layer of 2-in. polyiso foam on the exterior.
“Why isn’t it more popular?” Lombardo asks. “Am I missing something?”
Those questions are the topic for this month’s Q&A Spotlight.
You’ll get a good, but not great, wall
According to GBA senior editor Martin Holladay, the main problem with steel framing is thermal bridging. Because the effect is so pronounced, all of the wall insulation should go on the outside. Insulation placed in stud cavities won’t accomplish much.
“You’re right that it’s possible to install two layers of 2-inch polyiso, giving you R-26,” Holladay writes, “That’s OK, but it’s not great.”
If Lombardo could add even more insulation on the outside of the wall — 6 in. rather than the 4 in. he has proposed — he’ll end…