Minimizing Indoor Air Pollution

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The Bower family needed a home that was free of indoor air pollution.

Our house was designed to minimize indoor air pollution. While such a house is probably a good idea for most people, it was an absolute necessity for my wife, Lynn, who is extremely sensitive to the many pollutants that our society takes for granted. She cannot tolerate such things as exhaust fumes, household cleaning products, synthetic fragrances, and printing ink. Scientists are in agreement that these substances are toxic in high doses, but the growing segment of the population that exhibits symptoms at low doses was largely unexpected.

In fact, a commission at the National Academy of Sciences recently estimated that about 15% of the U.S. population may have increased sensitivity to low doses of pollutants. Symptoms vary tremendously depending on the individual and the toxin. In Lynn’s case, diesel exhaust fumes cause her speech to become slurred, while gasoline exhaust results in hyperactivity. Polyethylene sheeting, also a petroleum-based product, can trigger instant depression. Other exposures bring on other symptoms.

In 1976, Lynn and I bought and remodeled a multistory house built in 1850. The building had asbestos-cement siding and lead-based paint — typical pollutants in old houses. We gutted the interior and brought it up to 20th-century standards by adding such things as synthetic carpeting and new cabinets containing particle board. By the time we were finished remodeling, she was confined to bed. Her system was overwhelmed, and practically every organ in her body was affected. Today, though her health is much improved, she remains sensitive to many things and, as a result, is severely restricted in what she can do.

Getting rid of all the toxic cleaning products under the kitchen sink was easy. Buying 100% cotton clothing without any chemical treatments was more involved. Finding a building site 500 feet away from traffic fumes and agricultural chemicals took time. But the real difficulty came in actually building a home she could tolerate.

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.

We used ceramic tile throughout for the floor of the house. It is inert (nonreactive) and has proved quite attractive. I mixed the mortar and grout myself from cement, sand and water, to avoid the synthetic additives common to most premixed commercial products. The thinset did contain some undesirable ingredients, but by the time it was covered with tile and the joints were grouted, it proved tolerable. Cotton and wool area rugs are used instead of synthetic fibers.

There are no 100% nontoxic insulations available. In order to avoid outgassing chemicals, we used foil-backed dry wall over fiberglass insulation and took extra pains to seal around doors, windows and electrical boxes. As a result, the insulation is totally separated from the living space. All exterior walls were insulated, dry walled, and sealed before interior walls were built, to make sure that the barrier was complete. We used extruded polystyrene insulation under the four-inch concrete slab, which effectively seals the insulation from the indoors.

All the water supply lines are copper, but the drains are PVC plastic, which does out-gas. Similarly, residential electrical wire has plastic jacketing. These materials are inside the uninsulated interior walls, and we were unsure if they would present a problem. So, as a safety measure, I wrapped all such plastic with aluminum foil to minimize outgassing.

The paper facing on dry wall is made of recycled newspaper, which presents a problem because of ink residues. Fortunately, we were able to find a primer that effectively sealed the dry wall. Most commercial dry-wall joint compounds contain vinyl, fungicides, and antifreeze — all potential problems. We were able to use a specially formulated nontoxic compound made in Texas. The paint we selected was imported from West Germany. It is made from “all natural” materials, but it outgassed for three months after the house was complete. Eventually, the house aired out and became tolerable. Because of the problematic materials involved in dry walling, unpainted plaster could be used instead. It is more inert, but it’s also more expensive.

Most kitchen cabinets are built with particle board or hardwood plywood veneered with an attractive wood, such as oak. These materials outgas formaldehyde. So, I built all of our cabinets of solid wood. We chose tulip poplar because of local availability, cost, and appearance. The counter tops are stainless steel, instead of the usual plastic laminate over particle board. An extra-powerful exhaust fan vents the electric range, and a sliding pocket door can be closed to separate the kitchen from the rest of the house should cooking odors become unusually strong.

We placed the washing machine and dryer in a closet in the bathroom to keep the major moisture sources in one room. Custom-made porcelainized steel panels around the bathtub prevent the mold growth that is inevitable in the grout of ceramic tile. The toilet tank is insulated to minimize condensation, which could lead to mold growth.

Because the insulation values for the walls (R-40) and ceiling (R-45) are so high and the house is so well sealed, we have very little need for heat. Only 4,000 watts of electric-powered hydronic heat is needed to keep us comfortable.

We’ve lived in this house for nearly two years now, and Lynn’s health is slowly improving. There are still many things that she is sensitive to, but our house certainly isn’t one of them.

John Bower writes and lectures on safe housing and is the owner of a residential design/construction company called Ecologically Safe Homes.