Indoor air quality is the biggest factor in whether a house helps keep the occupants healthy or makes them sick. Attaining good indoor air quality isn't really so hard if you follow a few simple rules:
- Reduce or eliminate
- Isolate
- Ventilate
- Filter
The first rule is the most important. As with keeping water out for durability, keeping pollutants out is the first thing you want to do for good indoor air quality. That means not bringing in materials that offgas pollutants (e.g., urea formaldehyde). The heavier the pollutant load you have in the house, the harder it will be to have good air, so start here first. Along with that, make sure that pollutants from outside don't get in. In other words, make the house as tight as possible.
Second, there are always some materials you'll want to have on hand that could create a problem, so keep them isolated from indoor air. Paints, pesticides, gasoline, and other chemicals should be kept ideally in a separate building, such as a detached garage or shed. If that's not possible, then have them in a store room that's completely isolated from the house with a complete air barrier and no connection through the heating, cooling, or ventilation systems.
Third, after making the house as tight as possible, bring in fresh air. Mechanical ventilation with air brought into the house from a location where you know it will be clean is a great idea--and a necessary one for tight houses.
Finally, filter the fresh air coming into the house and the air circulating through the forced air heating and cooling system (if that's what you have). Notice that filtering is last in the list. Many people think of this as the first step in improving indoor quality, but you have to address the other issues first for maximum benefit.