POLLUTION-FREE HOUSING

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Many building materials release a variety of chemicals into the air as they age (this is called outgassing), and these fumes bother many sensitive people. New-car smell is a result of outgassing of upholstery and plastic. Formaldehyde is one of the major gases given off by carpeting, hardwood plywood, particle board and some insulations. Lynn is even bothered by the natural aroma of softwood framing lumber. Asphalt fumes from roof shingles are also a problem, as are most paints.

Though many experts blame high levels of indoor pollution on the trend to seal houses from air leakage, we decided to build our house as tight as possible. Every house needs fresh air. Some builders rely on random infiltration, but we have the advantage of being able to control and filter our air supply. Our house is well enough sealed that practically all exchanging air passes through a charcoal filter fitted to a heat-recovery ventilator capable of changing indoor air once per hour. Stale air registers are located in the kitchen, bathroom and all closets, and fresh air enters through a grille in the central hallway. In this way, good air circulation is assured, and all rooms are vented to the outdoors.

We usually run the fan on high for six to eight hours per day, and then shut it off in the evenings. But at times, as when a neighbor is burning trash, the filter can become overloaded. Then we simply turn the fan off until the outdoor air has cleared. Of course, the outdoor supply shouldn't be shut off for long periods, but we've had no trouble with it turned off for a couple of days at a time.

The frame of the house is made entirely of steel. Steel studs and joists are common in commercial construction, but they've never caught on for residential use. They have the general advantages of being lightweight, non-combustible and nonwarping. But from our standpoint, they also have no odor and eliminate the need to treat the house with toxic termiticides.

Aluminum siding and steel roofing further minimize outgassing. These products typically have baked-on finishes that are odor-free. Our windows are aluminum-framed. In the interest of energy efficiency, they are triple glazed, have thermal breaks in the metal frames, and most of them face south to take advantage of passive-solar heat. The entry doors are insulated with potentially problematic foam insulation, but their steel skins seem to seal very well.

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