Asthma and Your Home
by Arnie Katz
Q: My wife and I are getting ready to buy our first home. Both of us had asthma as children, so we think it's likely when we have children they might suffer from asthma. What are the things we should pay attention to in terms of finding a house that won't be a problem?
A: There seems to be widespread agreement on the fact that childhood asthma is an epidemic. Nationally, the number of children with asthma is 6.1 million. Asthma is the third leading cause of hospitalization among children under the age of 15, and is the leading cause of chronic illness among children. Researchers estimate that there are over 10 million missed school days per year in this country due to asthma.
No one really knows what "causes" asthma, but physicians and health workers know a lot about what triggers asthma attacks. Various air pollutants, such as tobacco smoke, are known to trigger asthma attacks. Substances that often get into the air, such as dust, pollen, mold spores, cockroach parts, and dust mite parts, are known asthma triggers. There are a number of studies indicating that unvented combustion appliances also contribute to asthma. In millions of people who don't have asthma, breathing these substances causes allergic reactions ranging from mildly annoying to seriously debilitating.
In building a new home that will be will be a healthy place for your children, then, you want to make sure pollutants have trouble getting into the house, and that those that do can be removed or at least separated from the people. There are several basic things to do to achieve your goals, most of which are not commonly done.
Make sure the house is built tight by having it tested. The test, called a "blower door" test, uses a large calibrated fan to pressurize the entire house and measure how tight it is. There's no reason to guess about this any longer. Similarly, make sure the ductwork for the heating and cooling system is well-sealed with mastic (not tape) and is pressure-tested. Leaky ductwork often sucks pollutants into the house and can also increase the leakage in the house shell itself.
Next, make sure the insulation is done correctly. This means no gaps, voids, compression, or places where outside air flows through the insulation. Typical insulation installation often leaves cold spots where condensation can occur, leading to mold growth. Mold is one of the worst asthma triggers.
The most important thing to do to keep mold out of the house is to keep the house dry. Careful foundation drainage, damp proofing, gutters and downspouts, grading the land away from the house, and proper flashing all help to ensure water doesn't get into the house. A poly vapor barrier should be used on the ground of a crawl space or under a concrete slab.
Almost all the asthma triggers require relatively high moisture levels to grow and thrive. Keeping the moisture and relative humidity levels down are the most effective ways to reduce the amount of asthma triggers in the house. Properly building the house shell to keep water out is crucial. Designing the HVAC systems right to remove excess moisture from the house and to remove particles from the air is also crucial.
For instance, air conditioning systems are typically over-sized. This "Bigger is Better" mentality means that in many homes the units don't run enough to de-humidify the air in the house. Make sure your system has been designed using a real heat loss/heat gain calculation for your house. This is rarely done.
Similarly, most bathroom fans make lots of noise but move very little air. It's very important to get bath and kitchen fans that are quiet enough to use without irritation and that actually move at least 50 CFM (cubic feet per minute) of air out of each bathroom and 100 CFM out of the kitchen. These high-quality fans may cost 3-4 times the basic builder model, but they actually work and will remove the moisture from bathing and cooking. Recirculating range hoods do nothing to remove moisture from the air, which increases the risk of asthma. A whole-house ventilation system, with dehumidification, may be worth considering also.
Think also about using materials that are easy to maintain. Concrete, tile, wood, or vinyl floors are easy to sponge off, compared with carpet, which tends to collect dirt and dust and critters like dust mites. Surfaces that are easy to clean are less likely to hide crumbs that attract cockroaches. A central vacuum cleaner system exhausted to the outside removes a lot more particulates from the air in the house than standard machines, many of which spew fine particles out the back where they hang around in the air waiting for you to come by and breathe them in.
Once you've got a house that's tight and dry and easy to clean, install a good filtration system, such as a 6" pleated media filter on the HVAC system. Some electronic filters are also good, but they need regular cleaning and sometimes produce ozone, which is a lung irritant that may not be good for asthmatics.
Finally, make sure any combustion going on the house is vented to the outside. If the house has an attached garage, either the house-to-garage connection must be extremely tight or an exhaust fan should be installed in the garage to keep it at a lower pressure than the house. Gas ranges must have a range hood vented all the way to the outside. All furnaces, water heaters, space heaters, and fireplaces should be sealed combustion units vented all the way to the outside.