Wednesday, January 6, 2010

What Makes A Healthy Home? — Alan Gibson

Once at a building conference I heard about the results of a study on air quality. The study said the air quality inside the average new home in rural Wisconsin was 8 times worse than the air quality outdoors in New York City. This blew my mind. How could that be true? And then I heard more and read more about how toxins and pollutants can build up inside a home and, if there’s poor ventilation, reach unsafe levels in the air. Rates of asthma and other respiratory diseases have been on the rise in this country, and while industrial pollution is certainly a factor, the way houses are built and furnished is probably a bigger factor in the decline of respiratory health. As part of the team designing and building the homes for Belfast Cohousing and Ecovillage, I’m working to ensure all the homes are as healthy to live in as possible.

How can a home be less toxic? Conceptually it’s very simple—reduce the nasty stuff inside and bring in plenty of fresh air. Practically, though, it’s not that simple. On the material side, builders have gotten away from good old-fashioned building materials like solid wood, plaster and stone, and for some good reasons: they’re expensive and poorly insulating. But when these materials are replaced with particle board, fiberglass, vinyl and synthetic carpets, the home buyer is spending less money and probably using less energy for heating, but at the same time a lot of volatile organic compounds, formaldehyde, and other toxins have been introduced to the interior air. And in an effort to reduce energy use, builders have been trying to make buildings more air-tight and less drafty, which improves comfort as well as the utility bill. However, the combination of the tighter envelope and the off-gassing interior finishes is what leads to sick people in Wisconsin (and other places). So now we’re back to turning the conditions around, being aware of what we put in the house and making sure we ventilate properly. It is now relatively easy to find out if a building material is air-quality friendly. Several ratings agencies exist to test and determine the safety of various materials; an architect can specify formaldehyde-free or low-voc plywood and paints; natural linoleum is available as an alternative to vinyl flooring; people should know better than to put carpeting in a damp basement. On the ventilation side, agencies such as the American Society of Heating, Refrigerating, and Air Conditioning Engineers studies indoor air quality and issues standards for rates of ventilation. They have formulas for determining how much fresh air to bring into the house over time to ensure proper fresh air supply.

More specifically, in the homes G•O Logic builds, we install a complete, ducted ventilation system that delivers fresh air to bedrooms and living spaces and removes stale air from the kitchen and bathrooms. The incoming air passes through a heat-recovery unit that transfers almost all the heat form the outgoing air to the incoming air, which means there’s very little energy penalty for the healthy ventilation. We determine the proper ventilation rate based on accepted standards. For example, in the 1500 square-foot model home, we will ventilate at a rate of 70 cubic feet of air per minute, continuously. This means the entire volume of air in the house will be changed once every 3 ½ hours, ensuring healthy air quality for a family of 4 or 5. And on the material side, we specify only low or no-voc materials and finishes. The floors are either polished concrete or solid wood; cabinets are formaldehyde-free. The building is incredibly air-tight, which helps tremendously in the energy-efficiency and comfort of the home, and when coupled with the ventilation system, results in a home that’s both super-efficient and healthy to be in.

Alan Gibson


  1. I'd like to suggest that occupants should test their own indoor air quality. Why? Even if the home is constructed with low VOC materials and has proper ventilation, there is no way to know what people bring into their home. I have seen fuzzy hangers raise the formaldehyde in a master bedroom closet to 450 ppb. I've seen expensive name brand furniture raise room air to 350 ppb. Unfortunately, the examples are endless.

    Testing is easy and low cost, $39 including lab analysis. Simple do what the Sierra Club did to discover the FEMA trailer issue. Obtain passive acs badge for formaldehyde, slide the cover down exposing a series of holes, hang in the center of area being tested, wait 24-hours, slide cover close and mail. In a wee the occupant will get the results and know if they have a problem.

  2. So, opening the door(s) works fine too except it wastes the energy (fossil, solar, biomass as may be) stored in the structure as heat. And when the power goes out, we are back to opening the doors and windows anyway to ensure adeqate air exchanges. What if the house isn't built so airtight. What if we all just decided that living in an intelligently designed less than airtight home kept between 54 (nightime) and 64 degrees was OK? In that case couldn't we develop passive air exchange systems? Oh, just a minute, we got doors and windows :)!

  3. I feel weird about the foam panels used to construct homes. I don't want to live in a styrofoam box! Doesn't sound healthy, even if the window is open. Unless the foam is the new soy based one... then never mind!