Steel Framing and Mold in Houses

Steel Framing and Mold in Houses

I read your article “Steel or Wood Framing, Which Way Should We Go?” in the Volume 3, Number 4 issue of EBN with considerable interest and anticipation, but did not see a sufficient discussion on the major reason for building differently with steel studs: the problem of mold growth at the thermal bridge over studs. The requirement to avoid local cold spots so as to prevent mold growth (mold being the major indoor contaminant in most homes) is MUCH more restrictive than a heat loss calculation would identify. People should not live in moldy homes! Steel studs are not just like wood. Steel studs may end up being the way to build very energy efficient and healthy homes, but not by substituting them piece-by-piece for wood. Some considerable redesign is needed to compensate for the unique properties of steel. Your article stated that, of course, but did not give sufficient emphasis to the severe health implications in some climates. Local cold surfaces in higher-humidity houses could result in serious mold growth problems after the first few cold months.

People do not need more exposure to mold; they need less.

When we built our house for the environmentally-hypersensitive we went with a wall system that placed all of the insulation outside the wall studs. They were wood in our house but could easily be steel if it were properly degreased. If the steel studs are fully within the insulation, they operate at temperatures very close to indoor air temperatures and will not cause significant thermal shorting effects. They will not contribute to a heat loss problem nor a local mold growth problem. They will be no problem.

I have great hopes and expectations for steel studs in healthful homes, but the present thrust to do a piece-for-piece substitution may end up giving steel studs such a black eye (to go along with the black lines on the drywall) that this promising form of construction may go into permanent disrepute. That would be a shame, but just what the steel marketing people deserve if they do not take the local thermal anomaly problem seriously enough. If you don’t know your marketplace well enough, it can reach up and bite you. In this case, the bite could be fatal.

Finally, I would again like to make a plea to all of you who are working towards a better environment. Remember that the indoor environment always takes precedence over the outdoor/ambient one when people are concerned. It is indoors that we receive our worst exposures. Choosing ambient environment measures that make indoor environments worse is not right. I would never suggest that we ignore outdoor environments and the health of the planet that gives us life. I worked in manned space programs far too long to be unaware of how silly and exorbitantly expensive it would be to make our indoor environments healthy when the outdoors was no longer supportive of life. We would not survive as a species if we went that route. We must, however, choose ambient protective solutions that respect the need for better indoor environments as the over-riding priority.

Steel studs could make indoor environments much worse if they are not used properly. They can help make those indoor environments better if they are wisely used. The choice is ours. Let’s make the right one. While I have not discussed the problems of misuse of steel in hot and muggy climates, they too are of concern. Finally, keep up the good work!

Jim H. White

Senior Advisor—Building Science

Canada Mortgage and Housing Corporation

Ottawa, Canada