Sick Houses: Using Diagnostic Tools to Improve Indoor Air Quality

These unusual mold species growing in a refrigerator tray are among the many indoor air pollutants found in an Energy Options Northwest audit. An environmental audit is one way to identify and eliminate the sources of such pollutants.

Dan Wildenhaus of Energy Options Northwest uses a Duct Blaster and stage fog to smoke out duct leaks. As in energy air sealing, environmental air sealing has to place special emphasis on defining the building envelope.

One client reported ongoing health problems related to his home, especially the living room. Energy Options staff found a 6-ft2 section of flooring under the carpet, covered with black mold that had built up over a number of years. A faulty window seal was the source of the moisture.

Environmental technician Gary Smith uses foil tape to seal the wall/floor joist behind the carpet. He sealed with tape instead of caulk because the client in this home was environmentally sensitive and unable to tolerate the chemicals present in caulking compounds.

James Estep uses a HEPA vacuum to clean a duct system. He is employing a special method of duct cleaning which uses a fan to force pollutants towards the furnace, where a powerful filtering vacuum is in place to remove them. This method is particularly recommended for people with environmental sensitivities.

An environmental technician uses hazardous waste containment procedures while removing carpet from this room. The room is separated from the rest of the house with visquene plastic and held under negative pressure, as protected workers wrap up each roll of carpet.

An increase in reports on the health effects of exposure to pollutants in the workplace, in schools, and in our homes is hardly surprising. Indoor air pollution has been ranked by the EPA as our most prominent environmental problem; a Massachusetts Legislative Special Commission has said that it accounts for 50% of all illness. Reports of sick building syndrome, a recent phenomenon, have been rising at an alarming rate.

Meanwhile, back in the world of energy conservation, the past decade has seen great advances in our understanding of building performance. The use of blower doors, pressure diagnostics, and targeted air sealing has evolved from a crude hole-plugging service to a holistic art and science that concerns itself not only with energy conservation, but also with comfort, building durability, and indoor environmental quality. Some of the diagnostic techniques and management tools developed for weatherization can be applied to solve indoor environmental problems.

At Energy Options in Seattle, Washington, we noticed early on in our weatherization practice that the homes we weatherized that had the worst structural and duct air leakage problems also tended to be the homes with most complaints about dirty air, allergies, and chronic illness. Long hours spent air sealing in crawlspaces and attics cannot help but impress one with the poor air quality in these areas, and how freely air moves between these spaces and the interior living space in many homes.

Bringing this training together with the experience from our energy conservation work, we established two simple guidelines in approaching home environmental problems. First, our role is to treat the building, not the occupants. Interested as our clients seem to be in describing their symptoms to us, the causes of diseases are very difficult to establish, and we are not physicians. However, knowledge of our client's specific allergies and chemical sensitivities can be important in determining how aggressively we need to pursue various pollutant sources. Our job is to listen attentively and objectively, separate preconceived theories from useful observations, and keep our focus on the house.

Second, we leave air sampling and chemical testing and their interpretation to the chemists and toxicologists. Often air quality problems can be solved by using simple environmental sleuthing tools--sight and smell, pressure testing, and sound building science. If not, then air testing will be more effective at uncovering a hidden pollutant after the obvious hazards have been cleaned up.

As in energy management, the key to solving environmental problems is control. Our approach is to gain control in three critical areas--air sealing, ventilation, and eliminating sources of pollution.

Environmental air sealing is similar to air sealing for energy conservation purposes, with special emphasis on defining the envelope at the point where air quality control is lost. A below-grade basement, for example, which would be included inside the thermal envelope, might be excluded for environmental purposes if mold could not be kept under control year-round. Controlling air quality requires knowledge and control of the amount, source, and distribution of fresh outside air which dilutes pollution concentrations in the home. Finally, our environmental audit is designed to identify all possible sources of pollution on the site--within the living space and in the zones connected to the living space, such as the crawlspace, basement, attic, attached garage, porch, and duct system.

Our investigation is designed to identify areas in the home environment that are not controlled. We find out what we can about the house from the occupants--its history, its problems, and how the mechanical systems are operated. We want to know about possible sources of pollution in the neighborhood--a main highway, a bus terminal, a dry cleaner, local use of pesticides. We need to know about any water problems--does the site drain, and are the basement and crawlspaces dry year-round? Have there been any leaks on the roof or in the plumbing? We measure the structural air leakage using a blower door, and run pressure diagnostic tests to determine the relative connectedness of the crawlspace, garage, attic, and any other zone to the living space. If the house has a forced-air heating system, we use a Duct Blaster to measure and analyze duct leakage. We check the relative humidity in each zone. We run combustion safety tests and measure the carbon monoxide level emitted from each combustion device. (Combustion safety tests include testing for backdrafting.)

This systematic approach has been successful in solving a number of home environmental problems, sometimes without positively identifying the source or sources. For example, Mrs. G. had tested positive for allergy to dust mites, cats, and mold. After researching the subject on her own, she had the bedroom carpet removed, excommunicated her cat, purchased a HEPA vacuum cleaner, and had an electronic air filter installed in her furnace. Still, she spent the winter sneezing and suffering from a chronic sinus infection.

Our audit identified some significant problems. There was severe air leakage (approximately 25% of the total) between the house and a very dusty attached garage. A large open cavity in the attic around the fireplace chimney accelerated infiltration through the basement and the garage. Squirrels had created a 4-inch hole in the roof, causing water damage and mold growth in an interior wall; and many books and knick-knacks on shelves in the master bedroom offered unnecessary horizontal surfaces for dust collection. Open fireplace dampers exposed the creosote-encrusted chimney throat to the home interior; an electronic air filter was inefficient because it was inadequately maintained, and furnace ducts and plenums were dirty.

In response to our audit, Mrs. G. got rid of the bedroom dust catchers, had the roof repaired, had the ducts cleaned, and our crew installed a fresh air duct to the furnace return plenum with a clock timer set to run intermittently for 12 hours per day. Though we could not say exactly what had been in the air that was bothering Mrs. G., a general clean-up of easily identified sources solved her problem. She reported immediate improvement in air quality and her symptoms subsided.

In an effort to escape the stress of urban life in Seattle, Mr. and Mrs. B. built their dream house in a quiet fishing village 60 miles north, on the pristine shores of Puget Sound. Ten years later and after numerous tests and doctor's visits, Mr. B. decided something in his house was making him sick. By the time he called us, the problem had forced him to spend most of his time on his boat. When he told us he particularly avoided going in the living room, we intensified our search there and found a 6-ft2 section of flooring under the carpet covered with black mold. This was caused by a faulty window seal that had allowed water to leak down the wall for years. We also found several species of mold growing in the crawlspace from previous plumbing leaks and poor ground cover.

The window leak was repaired by a glazing contractor. We removed and replaced the damaged wall, flooring, and carpet (using hazardous materials disposal procedures). We scraped and treated all moldy surfaces in the crawlspace, installed new ground cover, sealed the underfloor and foundation walls, and installed a fan to continuously depressurize the crawlspace. We also installed a fresh-air duct and timer on the furnace. When we checked back a month later, Mr. B. was back in his house and breathing comfortably.

Most ground cover/vapor barriers have been contaminated with mold and need to be replaced. We seal the crawlspace from the living area, using pressure to find the floor penetrations, and make sure it is well vented to the outside. In the event that the underfloor is un-sealable (for example, if it is shiplap or car decking), if moisture cannot be controlled year-round, or if an occupant is mold sensitive, we may opt to seal the crawlspace foundation wall as well as the underfloor, and ventilate mechanically.

This strategy, similar to the subslab depressurization technique used in radon mitigation (see below), creates a negative pressure in the crawlspace, preventing upward migration of mold spores and other contaminants into the living space. We have completed eight of these jobs to date, with generally excellent results in mold spore reduction in the living space and reasonable control of the relative humidity of the crawlspace.

Radon is a naturally occurring radioactive gas resulting from the decay of radium; it is the second-leading cause of lung cancer. The U.S. EPA estimates as many as six million homes throughout the country have elevated radon levels. Radium is found in the geologic strata of some areas of the country. Short-term testing is the quickest way to find out if a potential problem exists. Low-cost radon test kits are readily available in hardware stores or through mail order.

Corrective measures include sealing foundation and slab cracks, improving whole-house ventilation, and maintaining a continuous negative pressure below the slab. These strategies should only be undertaken by those who have had specific training in radon mitigation.

An unfinished basement is treated like a crawlspace. The control strategies are similar, except that since a polyethylene vapor barrier cannot be used to control moisture, different strategies are needed.

Wall and floor coverings in a finished basement can mask conditions, making investigation more difficult. Here is where we find a moisture counter very useful for measuring moisture content of drywall, wood, or concrete.

Most people are conscientious about storing their most hazardous materials--such as pesticides, gasoline, paint and solvents--out in the garage with the car. Unfortunately, most attached garages are 25%­75% as connected to the house interior as they are to the outside, primarily through the common wall, the joist cavities above it, and the forced-air ducts. We advise our clients to buy or build a detached storage shed for hazardous items, and to never start the car with the garage door closed or let the car idle inside the garage. Another solution is to store hazardous materials in a metal cabinet ventilated to the outside. Targeted air sealing can also reduce air communication between the home and garage to a minimum.

Attics

The most common problem found in attics is air leakage--from open chases, bypasses, and penetrations--which accelerates the stack effect, drawing air up into occupied rooms from the crawlspace, basement, and garage. We have also found the attic to be the source of many mold spore problems, from a leaky roof or from moist interior air getting in and condensing against the roof deck.

In the home's interior we conduct a thorough search in every room for signs of moisture or mold, pests, lead, dust, formaldehyde, asbestos, and hazardous household products. We look for damp spots or stains on finished surfaces, or use a moisture counter. Large amounts of mold can be detected by smell. Pests give their presence away by their burrows, nests, or most commonly, the pellets they leave behind. If the house was built before 1960, we assume that the bottom layers of paint contain lead, or we use a quick Lead Check® swab containing a compound that reacts to lead. We guess at the presence of formaldehyde based on the amount of exposed particleboard in the house. We look for light-colored cloth tape on ducts from the 1920s-1940s, cement board siding from the 1950s, square vinyl floor tiles from the 1960s and 1970s, and popcorn acoustic ceilings from the 1970s and 1980s. We often take samples of these materials and recommend testing for positive identification.

Special attention is paid to bedrooms, where most people spend about a third of their time and the ventilation rate tends to be the lowest. The most commonly recommended interior improvements include removing and replacing old carpet and sealing particleboard shelving. When removing carpet or building materials containing mold, we use hazardous containment procedures similar to those employed for asbestos removal. The HEPA filters used for asbestos removal are generally not deemed necessary for mold or carpet removal.

Mrs. P. developed rhinitis and a chronic cough soon after moving into her new house in West Seattle. Her symptoms subsided in the spring and came back in midsummer, when her air conditioning came on. Duct BlasterTM tests told us that the equivalent leakage area of the return duct (located in the crawlspace) was 201 in2, or about 1.4 ft2. With a 3-ft2 opening at the two return grilles inside the house, the furnace was drawing approximately one-third of its air from the crawlspace! Our inspection of the crawlspace revealed small pools of water fed by underground springs under the ground cover, and several types of mold growing on the ground, foundation walls, and floor joists. It didn't take long to figure this one out. We sealed the holes in the underfloor and reduced air leakage in the return duct to 17 in2. As soon as the drainage contractor installs a sump pump, we will return to remove the mold and replace the ground cover.

Exhaust ventilation draws replacement air from wherever the house leaks, (which may be from the crawlspace, from the garage or down a chimney). This makes it impossible to control the quality of incoming air, so we install supply-only whole-house ventilation, which brings air from the outside to the inside, rather than vice versa. Air is drawn in through a pleated-media or bag filter, creating a slightly positive pressure in the house and reducing infiltration of pollutants from outside. In our mild climate, we have seen no condensation problems resulting from this practice. For a person with multiple chemical sensitivity, we may install a powerful filtration system with activated carbon and a HEPA filter, which can stand alone or be ducted in parallel with a forced-air heating system. For those who prefer passive ventilation, we can help design a window opening strategy to match various weather conditions.

In some cases, the client may start by having only the highest priority improvements completed; we monitor the results and continue with lower-priority items as needed. We check back with our clients after three months and again after one year. If our control strategy has not achieved the desired results by then, we recommend air sampling or other testing to sniff out any remaining sources of pollution.

The health implications of the environment we have created can't be fully known or predicted at this point. But we've found that a systematic approach using the analytic tools developed for weatherization, along with common sense, may at least improve the quality of the indoor environment, and at best turn a sick home into a healthy sanctuary.

Scott Finley is an indoor environmental hygienist and the owner of Energy Options Northwest.

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