Canadians bemoaning the stress and frustration of renovating their homes may be amazed to hear that their construction nightmare is nothing compared to the problems faced by environmentally-hypersensitive individuals merely trying to create a living space that will not make them sick.

"So many things can go wrong along the way [during construction], but one mistake and an environmentally-sensitive person cannot live in the house," said Virginia Salares , Senior Researcher with the Housing Technology section at Canada Mortgage and Housing Corporation (CMHC). "Sometimes ideals may not be realized. A person building must be sure to know everything that goes into a house as costs escalate. There are so many lost opportunities when taking the usual, and cheaper route in construction."

According to the Canadian Lung Association, 20 per cent of Canadians have some type of lung disease including asthma, emphysema, or lung cancer. When those with allergies and environmental sensitivities are included, up to a third of Canadians may be affected by contaminants. For adults and children with environmental hypersensitivities, even low levels of contaminants in indoor air may cause debilitating illness.

Just as people with environmental hypersensitivity have exacerbated reactions to their environment, the problems they face in construction and renovation are aggravated by the challenges and frustrations that seem to have become commonplace for consumers.

When money gets tight or funds run out during construction or renovation, the resulting short-cuts and cost-cutting measures can destroy the environmental integrity of the house. This may cause problems for most property owners, but for those with hypersensitivity, disaster may follow. For instance, plaster walls are preferable for hypersensitive people compared to the less-expensive dry wall which may harbor molds if exposed to excessive moisture.

Sometimes problems are caused by inexperienced or negligent construction workers. One person with hypersensitivity found a suitable house, had it moved onto a new foundation to improve air quality and added a geothermal unit to create an environmentally tolerable place to live. However, the geothermal unit selected used highly toxic methanol instead of the more benign ethanol. Faulty installation caused this chemical to leak into the basement and to permeate the whole house. The homeowner became so ill that hospitalization was essential for recovery. In another case, plumbers delayed connecting a toilet for so long that mold entered the system and contaminated the house.

In a surprising reversal, interior air quality is often considerably poorer than the outside air. The principles commonly employed to reduce residential environmental contamination must be more rigorously applied when hypersensitivity is an issue, including:

• Select very low emission materials with the least toxicity (for instance, solid wood kitchen cabinetry instead of particle board) to reduce the release of chemicals like pesticides, formaldehyde, and adhesives.

• Install and maintain superior ventilation equipment. The ventilation system must supply well-filtered air to the bedroom and living room and remove air efficiently from any location that could have an offensive odor, or be a source of excessive humidity.

CMHC's Research House for the Environmentally Hypersensitive , a model home where the air is free of dust, mold, pollen, and chemical vapors, demonstrates affordable methods of achieving clean-air housing that are ideal for those with respiratory problems and environmental hypersensitivities, or anyone concerned about the air quality in their home. The demonstration house, built in Quebec when hypersensitivity research was funded between 1991 and 1996, was later moved to Ontario's Ottawa General Hospital grounds, where it will eventually be used to encourage asthma sufferers to make similar modifications to their homes.

Although site-built houses are designed, or modified to meet the special needs of those with environmental hypersensitivity, CMHC launched the demonstration because prefabricated houses were not being built in Canada to combat this problem. Factory-built homes offer production economies that can result in more affordable, individually-customized and consistent-quality systems, but this type of housing is still not being built on any scale.

Salares stresses that the burden of designing, financing, and building a home that does not cause reactions in environmentally-sensitive individuals must be carried by those who will live there. One strategy to balance off the added costs of creating homes to combat hypersensitivity is to build smaller, simpler homes that keep costs down and can be less vulnerable to contamination during construction. CMHC offers support in the way of research results and seminars on building to avoid mold, but consumers are otherwise on their own.

Experience has taught Salares some hard truths: "People have to be realistic about what they can afford, what they can build. If cost does not get out of hand, they can afford the cost of [environmentally-sensitive] materials. They cannot rely on a builder to make [choices] for them."