Steel Doesn't Absorb Water?

Environmental Building News since there is always something new and useful to learn.

Indeed, your July feature article (

Vol. 12, No. 7), “Moisture Control in Buildings: Putting Building Science in Green Building,” gave me something totally new to study and reflect upon.

Joe Lstiburek of Building Science Corporation has, for years, vehemently complained about the thermal conductance of steel framing. This is an acknowledged characteristic of steel, but not one without remedy, by way of a thermal break or other solutions. Now I learn that steel framing has another characteristic to dislike—its inability to absorb water.

Wood framing, in contrast to steel, can freely absorb and dispel moisture, like a humidity flywheel of sorts. As reported in your article, “wood-framed walls can be superior to steel-framed walls” because “wood framing helps to regulate moisture in buildings.” The reader should be alert and responsive to such keen observations. We apparently heard it here first: Steel does not absorb moisture!

Obviously, this gives the steel industry a new challenge to overcome. The mind boggles with options. Right now, I am thinking of small sponges secured inside each steel stud. Perhaps for climates with especially rainy seasons, a Velcro strip could be provided so that, at certain times, a supplementary sponge could be placed in the wall compartment, via a special access door.

The mention of “door” reminds me of the basement door in my wood-framed house in Pittsburgh. The wooden door seals shut in the summer in its wooden sash, because it absorbs moisture from the air. This provides an added security benefit during the summer, when I might be away on vacation. In the other seasons, though, I have to rely on ordinary locks. Now, from this article, I know the swollen door is regulating moisture that would otherwise be lurking within the house. With more wooden doors, upstairs and downstairs, comfort would be even better!

Other thoughts come to mind, but I must close to pursue exhaustive scientific research that might yield a new moisture-absorbing steel or, at least, some inexpensive options (well beyond sponges!) to compensate for this new-found deficiency. For better building design, however, we will look to the other interesting and more valuable information on moisture control in the balance of the article that was, as always, thoughtful and enlightening.

Gregory L. Crawford

American Iron and Steel Institute

Pittsburgh, Pennsylvania

Joe Lstiburek responds:

The problem with trade organizations is that they tend to be one-dimensional. The steel industry refuses to believe that steel is conductive and rusts; the wood industry refuses to believe that wood burns, rots, and is dimensionally unstable; and the concrete industry refuses to believe that concrete cracks, shrinks, and spalls.

We at Building Science Corporation do lots of stuff with steel. We just don’t insulate within a steel-stud cavity: It’s a dumb idea. We love insulating the outside of steel studs with insulating sheathing. The most mold-resistant, practical wall assembly is an empty steel-stud cavity wall with Dense Glass Gold on the outside as a sheathing, covered by a drainage-plane membrane and semi-rigid fiberglass or rock-wool insulation and just about any cladding system (that is also back-vented). The interior cladding is a non-paper-faced interior gypsum board. We recommend this for commercial, institutional, and premium residential construction. And, by the way, this assembly works in virtually every climate: Mold does not grow on steel, and a little rust is not in the same league as a little mold.

The steel industry just doesn’t get it. They are never going to compete on a “stud-by-stud” basis with wood. The whole approach to wood framing is based on the unique properties of wood—some of which are good and some bad. Steel has different properties than wood, so systems optimized around the unique properties of steel should look different than wood systems.

Now, I would love to have a couple of beers with these guys. I actually want to reduce the amount of wood in buildings—and one of the ways is to use steel. I also want to reduce the amount of concrete in buildings—and one of the ways is to use steel. And I want things to be put together faster—and one of the ways is to use steel. We might actually be able to work together if they can be a little more open-minded. I’ll buy the first round.

Joseph Lstiburek, Principal

Building Science Corporation

Westford, Massachusetts

Editors’ Note: The above exchange was edited for length and to maintain our publication’s family-friendly rating. We’re pleased to report that the proposed meeting was agreed to and is slated to happen at the Energy & Environmental Building Association (EEBA) conference in Chicago this October.