Turn on the fans. Leave the finishing to the factory. Plan those HVAC runs as if your livelihood depends on them. In case you haven't heard, there is an exploding number of asthmatics and people with allergies out there. It's time to come clean. By Matthew Power

New studies from the EPA suggest that one in three people who purchase a home today have someone in the family with allergies. With "tight" homes now essentially mandated in virtually every building code, and mold litigation on the rise, addressing indoor air quality is no longer an amenity. It's a survival skill.

Steve Klossner, technical consultant for the American Lung Association, has done extensive work on indoor air quality. Most of his work has been forensic: figuring out what fouled the air in an existing home.

"If you ask me to name the top three indoor polluters," Klossner says, "the first would be water intrusion, without a doubt. Next would be combustion by-products. And finally there are the particulates we all create."

Working the systems

Good indoor air quality starts with minimizing entry of water into the home and removing excessive moisture. Once that step is taken, it's time to address critical systems such as air distribution.

"Newer forced-air furnaces and water heaters are more efficient, but that means they burn cooler, and more of the heat is going into the house," Klossner explains. "It also means weaker drafting [up the chimney]. This makes it much easier for combustion gases to backdraft into the home."

Compounding the problem, he says, is the fact that homeowners have been sold on excessively powerful ventilating fans for range hoods and bath fans. "What happens is that even if the furnace is venting properly, there's not a sufficient source of fresh air that can enter the house. You know where most of the fresh air comes from in many new homes? The attached garage. As you can imagine, that's not a good situation."

"Given today's tight homes, these fans are too big," he continues. "We're back into the 1970s way of thinking that bigger is better. A small fan moving 25 cfm of air can adequately ventilate a kitchen if it's run continuously. That's in the ASHRAE standard."

Unseen evils

You've heard about all the bad stuff floating around inside homes: bacteria, pet dander, dust mites, mold spores, and volatile organic compounds (VOCs), such as formaldehyde, paint fumes, and components in household cleaners.

For common household dust and particulates, whole-house vacuums (see Whole-House Solutions) have gained favor. A new Health House demonstration project from the American Lung Association includes a Beam central vacuum system.

As a general rule, anything you can smell is probably a pollutant of some sort. And the smallest, most deeply respirable ones, such as VOCs, may be the most dangerous, according to Klossner, because they stay in the body. They're also the toughest to filter by mechanical means.

One solution: Dissipate them before they ever enter the house. Another solution: Make certain they have fully outgassed before occupation. This can be done by commissioning (heating the house and ventilating it adequately), but Klossner warns that this technique can vary from extremely effective to not effective at all. "A bake-out may not work at all, for example, if you're heating a house in the Southeast in the summer and using humid outside air to ventilate."

Yet another solution: Coat materials that outgas with a "vapor lock" sealer. "We have sealed cabinets for years as part of the Health House program," Klossner notes. "Research shows that 75 percent of VOCs from the adhesives come through the end grain of the cabinets, where they never get any paint."

He adds, however, that cabinetry makes up a very small part of the surface volume in a home. "You really need to look at square footage of surfaces and compare that to total air volume to get an accurate estimate of sources of pollution."

In other words, you can get a bigger jump on indoor pollution by targeting products that cover the largest surfaces in the home, such as hardwood flooring, carpets, and painted walls and ceilings. "The best solution is always to keep the pollution from ever entering the living area," Klossner notes. Allow the products to outgas at a factory or other location outside the home. When that's not possible, a vast array of less polluting coatings and products is available--but choose wisely.

Hard science

It's widely assumed that low-VOC or no-VOC paints, for example, don't perform as well as VOC-laden latex standards. In some cases, that's accurate, says Klossner.

"In one extreme example, I visited a woman's house where the low-VOC paint had literally come off the walls," he says. "It turns out she was wiping down the walls every week with a damp cloth."

On the other hand, says Cedar Rose Guelberth, owner of Building for Health Materials Center, a national green building supply center in Carbondale, Colo., "there are products out there that are every bit as durable as professional-grade latex paints, but you have to know the difference between those and the ones that are crap."

Guelberth adds that buying "healthy" paints and solvents is a complex science loaded with pitfalls for the uninformed .

"Some of the products that are sold as low-VOC or no-VOC are ones that we consider more unhealthy for indoor air than standard paints," she says. "They have simply replaced the chemicals with other ones for which there is no testing. That doesn't mean the components of the product are healthy. The same goes for water-based paints. They're not necessarily better for you than solvent-based products." (For more about Building for Health Materials Center, see "Goddess of Green".)

Mechanical means

Whether as the result of outgassing or from the regular daily routine, all homes contain some pollutants. A system needs to be in place to remove them by means of either filtration or ventilation. Typically, a good solution requires a combination of the two.

In order for any filtration or ventilating system to perform well, however, it must run more or less continuously, with good distribution throughout the home.

"Unless the fan is running continuously on a furnace or HVAC system with a filter, it's not cleaning the air," says Klossner. "The other problem with most forced-air furnaces or central air conditioners is that they're designed to work with 99-cent filters. When you add a HEPA filter for example, it may not work. Often the air just goes around it, because the flow of the air handler is 600 cfm, and the HEPA filter may [have an airflow capacity of] 300 cfm."

Many homes in the Northeast have the built-in additional problems of baseboard heat and no comprehensive air distribution system, making air cleaning dicey, especially in winter months. A number of homes have no air distribution to bedrooms at all, Klossner says. In that case, homeowners would have to rely on small room-sized air filters.

A better solution for any new house, says Klossner, is to install a tightly sealed air distribution system. "Even 100 cfm of well-designed spot ventilation, running constantly, can remove most combustion by-products and water from the home."

Beware water! Water intrusion is enemy No. 1. To protect indoor air, foundations need waterproofing, not simply water resistance. Along with attention to the usual suspects--such as gutter systems and proper grading--foundations and slabs must be completely sealed with capillary breaks and caulking. Below slabs, an impermeable poly barrier is mandatory. If a gravity-fed drainage system is impossible, add a mechanical one indoors with battery backup.

Return to sender In homes without central air or heat, consider adding a duct network strictly for air ventilation and distribution. Seal all ducts to prevent air leakage. Good options include a central fan system with adequate fresh air intakes away from the attached garage. Be sure to include bedrooms in the air distribution cycle. They are a hot spot for allergy sufferers.

Favor the factory A hardwood floor prefinished in the factory not only arrives at the site with a tougher, baked-on finish but it has also completed most of its outgassing. If you must finish floors on site, consider a bake-out period. For carpets, use only low-odor premium brands, and unroll them outside the home before installation. Give them time to lose much of their odor. Attach to the floor using mechanical fasteners rather than adhesives. If you do use adhesives, purchase non-polluting alternatives.

Smooth the finish Avoid especially porous surfaces in the home where dust can collect and become hard to remove. Advise the homeowner that rough plaster surfaces--along with fabric wall coverings, drapes, carpets, and upholstered furniture--will make the task of removing allergens more difficult in the home.

Even the flow Specify HVAC systems that provide constant, steady ventilation. To save energy, you may install a whole-house fan, provided sufficient fresh makeup air exists in the house. Another option is a heat recovery ventilator (or energy recovery ventilators in the South), but the entire duct system must be tight and efficient for these to work adequately.

Filter out trouble When selecting HVAC equipment, look for models with tight seals around filter compartments and models designed to accept better quality filters. As a second line of defense against particulates, electronic filtration systems can be highly effective if regularly maintained. Choose only whole-house humidifiers with automatic thermostats that monitor outside temperatures and automatically adjust indoor humidity to safe levels. Also, put whole-house vacuums on the standard amenity list.

Mind the garage Attached garages provide an easy route for pollutants to enter the home. One solution: Create an "airlock" mudroom between the garage and the home, and put automatic closers on doors. Vent whole-house vacuums in the garage to the exterior. Consider linking an exhaust fan system to the garage doors. When they close, it runs briefly, removing exhaust fumes.

Whole-House Solutions

Whole house-vacuums can improve indoor air, but be sure to vent them properly.

A study last year at the University of California Davis School of Medicine looked at the impact of central vacuum systems on the lives of people with

Clean Machines
Central vacuums reduce nasal symptoms.
Central vacuum vs. baseline: 47% improvement
Central vacuum vs. conventional vacuum: 49% improvement
Payoff: Based on a quality of life questionnaire, researchers established a baseline for air quality health symptoms. Patients using Beam central vacuums noted a significant decline in nasal problems, more so than those using conventional vacuums.
Source:Journal of Investigational Allergology and Clinical Immunology

a hypersensitivity to house dust. The findings: Those who used the installed Beam central vacuum systems described marked improvement over their previous experience with non-centralized vacuums (see chart below). The systems improved their ability to sleep, lessened their nasal and eye problems, and even helped their emotional well-being. "These are great maintenance tools for the homeowner," says Steve Klossner, technical consultant for the American Lung Association. "I have just one issue with them--that builders tend to put them in the garage. If you do that, you positively pressurize the garage, and the garage air gets sucked into homes. You don't want that. But there's a simple way to fix it: Provide an exhaust outlet for the vacuum that goes out through the wall. The same would be true of putting one in a home's cellar."