By Katherine Salant
When your mother admonished you to pick up, dust, vacuum and join in her semi-annual cleaning frenzy, she wasn't just being a stickler for order. Clean houses are healthier because biological contaminants such as molds and dust mites are far less likely to get a toehold and multiply.
What's the big deal about molds? Although much about molds is still unknown, research has shown they can affect human health, explained Sandy McNeel of the California Department of Public Health. The susceptibility of individuals varies, but some people who live in houses with extensive mold growth can develop persistent flu-like symptoms; others develop mold allergies that cause classic hay fever symptoms such as runny noses and itchy eyes. It is not yet known if molds can cause asthma to develop, but mold can bring on added attacks in people who already have it.
Some molds produce a chemical that can be irritating to the eyes and throat and some produce toxins that can, on rare occasion, produce symptoms such as diarrhea, headache and vomiting.
When mold grows, it releases spores into the air. Adult exposure is almost entirely limited to inhaling the spores, but children and toddlers can get rashes and eye infections from skin contact with mold in carpets.
Mold spores are ubiquitous. They can't be kept out of a house. They can exist in any climate, even one as dry and arid as Arizona or Nevada. When building a new house, however, you have the opportunity to incorporate several strategies that can help to keep them at bay.
With sufficient moisture, molds can grow on almost any building material, so the first line of defense against them is moisture control, advised Richard Shaughnessey, an indoor air quality and mold expert at the University of Tulsa in Tulsa, Oklahoma. Venting to the outside should eliminate the substantial amount of moisture generated in kitchen, laundry and bathrooms. Most builders are required to supply exhaust fans in these areas, but some vent the moisture into an attic or a crawl space where mold can germinate and reenter the house.
When you visit builders' models, look for the exhaust outlets on the outside of the house. Stove exhausts should go to the outside, but often they do not and dryers exhausting into wall cavities are not unheard of, Shaughnessey said. The builder may say all the exhausts are vented to the outside, but you should verify this, he advised.
While you're outside, check that the grade around the house slopes away from it. Not only can water penetration damage the foundation, it can get into the basement and provide "mold sustenance."
On your tour through the house, turn on all the exhaust fans to see how noisy they are. Builders often install inexpensive ones that are so noisy that household members don't turn them on. When you finally settle on a house and a builder, consider upgrading the fans to get quieter ones that will be used.
Good ventilation with a constant replenishment of fresh air will help to keep down molds as well. As new houses have become increasingly tighter to meet energy efficiency requirements, the only way to insure a steady supply of fresh air in many cases is to install some type of mechanical means. This needn't be elaborate, however. Installing a continuously running 100 cfm fan unit in one of the bathrooms instead of the one that the builder would ordinarily install will supply adequate fresh air for a 2,400 square foot, four-bedroom house.
An ultraviolet lamp that kills spores and other bacteria can be added to the air handling system, but indoor air experts including Shaughnessey question its effectiveness. Though the light may reduce the number of mold spores, dead spores are just as allergenic and they can still cause adverse health effects, he said. Installing a high efficiency air filter that removes the spores altogether is a more sensible strategy. The air filter systems installed by most home builders are not very effective, catching only about 7 per cent of the particulate matter. An electronic air filter will zap about 80 per cent of it, including minute, micron-sized particles. The only catch is that you have to clean it periodically, but maintenance is required with any air filter system.
Then there's "source control." Most mold spores enter your house on your shoes. Catching them at their point of entry with a "walk-off mat" and a hard, but easily cleanable flooring surface by the front door will keep their numbers down and most production builders include this in their basic house. Asking family members to take their shoes off will also help. Wall to wall carpeting can harbor mold spores, dust mites, and other biologicals, especially if the indoor air is very humid or if the carpet gets wet. Reducing the amount of carpeting by installing hardwood floors or ceramic floor tile with area rugs will eliminate much of the area where these biological can thrive.
The least appealing aspect of mold control, which applies to both old houses and new ones, is the regular maintenance. Not only should the air filters on the furnace be regularly checked and cleaned, so should the coils on the air handling systems and the drain pan that is located just below the coil unit on your air handler. If this pan doesn't drain properly, mold can grow and the mold spores can be distributed throughout your house through the ducts. The drain pan under the frost-free refrigerator should also be checked regularly to make sure that it isn't blocked.
Using a vacuum cleaner with a high efficiency particle arrestance filter, commonly called a hepa filter, will trap dirt and eliminate it. Most standard vacuum cleaners redisseminate much of the dirt through their exhaust, rather than eliminating it, Shaughnessey noted.
Dust mites are another allergen than can be kept at bay with regular cleaning. Too big to be airborne for long (though their feces can be), they feed on the millions of skin scales that we shed everyday and they tend to concentrate in bedding. An impenetrable mattress cover and pillow casing will keep dust mites from establishing a beachhead there. Changing the sheets once a week and washing them in very hot water will also keep their numbers down.
In temperate climates, basements tend to become damp and moldy in the summer. Using a dehumidifier to remove moisture from the air will hold down mold growth, but vigilant maintenance is a must, Shaughnessey cautioned. Otherwise, the humidifier itself can become a reservoir for mold. The pan where moisture collects must be emptied regularly; if a hose is connected from the pan to a drain, it must be periodically checked to insure that it is draining properly.
Humidifiers that add humidity to heated spaces in winter can increase human comfort levels, but maintenance is an issue with these as well. If they're not vigilantly maintained and cleaned, they can cause adverse heath effects, Shaughnessey said. A room humidifier must be cleaned every few days, not every few weeks or months, he emphasized.
Humidifiers can be installed on furnaces, but these must also be vigilantly maintained; otherwise, mold will grow and air blowing through the duct system will disseminate it through an entire house.
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