How to Reduce Heat Transfer Through Steel Wall Frames
Steel wall frames are lightweight and economical, as well as recyclable, should the frame have to be replaced. However, they are also terrible for insulating homes against heat gain or loss. The R-value of the insulation in the home (basically, the score that tells you how well the insulation will work) drops dramatically in steel-framed walls, much more so than in timber-framed walls. This phenomenon, called thermal bridging, can lead to both annoyances like higher utility bills and destruction like mould and corrosion. If you are considering having a construction company build a structure with steel wall frames, look for one that addresses thermal bridging directly.
What Is Thermal Bridging?
Thermal bridging is the transfer of heat from one side of a structure to another as the heat travels from molecule to molecule. In buildings, that translates to heat loss in winter and heat gain in summer, both of which make the interior of the building harder to keep comfortable in terms of temperatures. Thermal bridging is common, and even structures with timber wall frames experience some thermal bridging, but not to the same extent as steel.
Why Is Steel So Much Worse at Handling Thermal Bridging Than Timber?
If you've ever grabbed a metal door handle in summer, you'll know exactly why steel wall frames have so much thermal bridging: steel is a fantastic heat conductor. That's not what you want in your walls, however, as that conductivity will transport heat to cooler areas, which are usually on the wrong side of the wall in any given season. To stop this transfer of heat, you need to separate the steel from other materials when possible and add materials that act as additional barriers to heat transfer.
Combined Sheathing and Insulation Acts as a Barrier
One strategy that's in use is to add a layer of material that acts as a combined sheath with insulation around the frame, rather than in the middle of and in between the frame's sides. By surrounding the frame with insulation and sheathing, you place a barrier between the frame and the outer wall material, blocking heat from transferring. You may still have some transfer, but it won't be as much. You can still place insulation in the middle of and in between steel frames, but if that's the only insulation, then the steel beams and posts are still exposed and touching non-insulation material.
If Possible, Add Air
You may also see special spacers added between the steel posts of the frame and the next exterior layer of the wall. This space helps reduce the amount of heat that transfers in or out of the wall from the steel. Air molecules do heat up, but they are less of an issue than steel.
Steel wall frames are still good to use in construction; you just have to insist that the construction company take steps to block as much thermal bridging as possible. Check which strategies the company uses and ask about additional reinforcement if the tactics in use don't seem to be enough.