A Breath of Fresh Air

Keeping Indoor Air Clean and Comfortable

by Dana Bres and Peter Ashley, for the PATH Partners

by Dana Bres and Peter Ashley, for the PATH Partners
illustration by Heather Guthrie

Clearing the Air:

It happens to everyone. You get a little distracted, overcook dinner, and then all evening, someone's asking, "What's burning?!"

Cooking odors are just one of the many ways bad air can linger inside your home. But many contaminants are odorless and go undetected by the human nose. We readily adapt to smells anyway, so your nose isn't a very reliable indicator of indoor air quality.

Besides odors, your home's air may also contain moisture, dust, mold spores, chemical fumes, combustion products such as smoke and carbon monoxide, and other potential irritants. Although most people aren't significantly affected by this indoor air cocktail, the long-term effects are still being evaluated. As anyone with asthma or other respiratory problems can tell you, poor air quality can become a serious matter.

If you're planning to build a home, you're in the perfect position to make it a healthy one by considering several techniques for improving indoor air quality. These techniques are recommended by the Partnership for Advancing Technology in Housing (PATH), a program of the U.S. Department of Housing and Urban Development that promotes efficient technologies to improve the quality, durability, comfort, and health of your home.

Choosing an efficient filter and replacing it when needed,
will reduce dust, pollen and other contaminants in your home.

Ventilation:

Healthy air starts with good ventilation. Without it, everyday activities like cooking (especially with gas), showering, and even breathing often make indoor air more polluted than the air outdoors. New carpeting and fresh paint or varnish can make it worse.

In most older homes, ventilation happens the old-fashioned way: through drafty doors and windows and small leaks in the walls and ceilings. To achieve better energy efficiency, today's homes are built "tighter" - so tight, in fact, that you may need to incorporate additional ventilation into the heating, ventilating, and air conditioning (HVAC) system to ensure healthy air. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends a minimum ventilation rate of 0.35 air changes/hour, which means that about a third of the air in your home should be replaced by outside air every hour.

If your home is built tight, you may want to consider an energy recovery ventilator (ERV). This energy-efficient device brings fresh air into the home and recovers the energy from the heated (or cooled) air as it is vented out of the house. ERVs make more sense the more extreme your climate is - whether hot or cold. They also can be used to control humidity, which is important in hot, humid climates in the summer and in cold climates in the winter. (In cold, heating-dominated climates, better air flow and the introduction of humidity to the indoor environment can help control wintertime window condensation. In humid summer climates, which are cooling dominated, it can be critical to dry out incoming air so that mildew or mold do not develop in ductwork.)

Heating and Air Conditioning:

Your HVAC equipment can help you maintain good indoor air quality and comfort. Correctly sizing both the air conditioner and furnace will not only provide better air quality and comfort, but also save you money on the initial purchase cost and your monthly energy bills.

Correctly sizing the air conditioner will help you control your home's humidity in the summer as well. Air conditioners provide the greatest comfort when they run long enough to both cool the air and remove the humidity. An oversized air conditioner doesn't run long enough to dehumidify the air adequately. You pay higher energy bills to run a bigger unit, and the air feels cold and clammy. So resist the urge to go with the "bigger is better" sizing strategy or the rule-of-thumb approach of one ton per 1,000 square feet. The builder should calculate the size of the air conditioner using Manual J, published by the Air Conditioning Contractors of America.

Many homeowners opt for radiant floor heating, which provides heat with hot water coils (or heat-generating electrical wires) buried beneath the floor. The heat is more even and, because there is no forced air to move dust around, rooms stay cleaner. PATH research has shown that radiant heat is as energy efficient as conventional heat. It's also very comfortable.

Regardless of the type or size of the HVAC system, maintenance is critical. Changing or cleaning filters is key to the performance of the system. A good filter will minimize the dust, pollen, and other contaminants that are introduced into your home. Normal filters remove dust and some pollen, but more efficient filters, including electronic, are available. Maintain your filters by changing or cleaning them at least twice a year - once in winter and once in summer. (Some filters require more frequent cleaning or replacement.) Routine maintenance is also critical to keeping systems operating at peak efficiency and, for gas furnaces, preventing exhaust leaks that can release carbon monoxide into the home.

Ask the Builder:

• How did you determine the size of the air conditioner and furnace?
• Did you use Manual J?
• Does my furnace use supply air from the outside?
• Where can we locate the furnace to provide the most useable space?
• What choices do I have for filtering the air in the HVAC system?
• Does an energy recovery ventilator make sense for our home?
• How much would an ERV add to the price, and how much would it reduce our yearly energy bill?
• Will upkeep be more difficult?
• How will you keep the ducts clean during the construction process?

Using an exhaust fan while cooking
helps remove odors, moisture and grease.

Controlling Humidity:

In most homes, moisture build-up is related to the owner's activities. A family of four releases about 2.5 gallons of water into their home each day. During the winter in cold climates, this moisture is often beneficial because heated winter air can be very dry. However, in other seasons and in areas where humidity is high year-round, this moisture can result in excess humidity, less comfort, and possibly mold or mildew. An indicator of excess humidity in a home is water condensation on the windows.

For most homes, the easiest way to control excess moisture is at the source, typically the stove or the bathroom. Exhaust fans will remove that moisture - but only if they're used. Family members may be reluctant to use noisy fans, so be sure to select quiet models.

Dehumidifiers are great for controlling humidity, which can cause mold and dust mites and trigger or aggravate asthma. However, unless your dehumidifier is vented outdoors - and most portable units are not - it will actually heat your home. During periods of mild temperatures, a dehumidifier might provide all the heat you need in your basement. Keep in mind that you may want to shut it off during the heating season when your home needs more humidity.

A ventilation control system can also be installed to control the air flow into the home and maximize the home's overall HVAC efficiency. More elaborate central air purification/ventilation/dehumidification systems can do it all, but of course, they cost more.

Basements can be an important source of home moisture. Take measures to prevent water from entering your basement by making sure your builder slopes the ground away from the foundation and extends the downspouts so they discharge away from the home.

Read more about indoor mold and mold control in "A Brief Guide to Mold, Moisture and Your Home," available at epa.gov (click on "Air,""Indoor Air," "Mold"), and in "Mold in Residential Buildings," available at toolbase.org (click on "Mold, Moisture, and Leaks").

Ask the Builder:

• Will we need to dehumidify our basement?
• Will a portable ENERGY STAR® dehumidifier do the job?
• Is a central air purification/ventilation/ dehumidification system appropriate for our home in this climate? How much more would that cost?
• How did you determine the size of the exhaust fans?
• Are exhaust fans ENERGY STAR® qualified? How quiet are they?
• Can the fans automatically shut off after running for a preset time?

Cooking:

While stoves have fans in the range hoods, many homeowners do not use them because of the noise. This allows cooking odors, moisture, and grease to stay in the home, decreasing air quality and requiring more cleaning. For kitchens, options for quiet range-hood fans include hood-mounted, in-line, or exhaust-cap fans. Just like selecting bathroom fans, selecting a quiet fan with the correct capacity is important. Again, ENERGY STAR® qualified exhaust fans are usually a good choice because of their low noise and excellent efficiency.

Ask the Builder:

• Is the exhaust fan ENERGY STAR® qualified?
• If not, how loud is it?

Cleaning:

Because indoor air quality often depends on the cleanliness of the home, select building materials that are easy to clean. Smooth floors - such as wood, laminate, tile, bamboo, or pigmented concrete - provide such surfaces. Low-pile carpet is also easier to clean than deep-pile carpet. (See "Building Technology 101: Flooring for a Healthy Home and Planet" in the Winter 2005 issue of Her Home.)

We have all used a vacuum that leaves a dry, dusty odor in the room after use. That odor is the dust leaking from the bag back into the room. If you use a portable vacuum, choose a model with effective air filtration to prevent the release of small dust particles. Some models offer High Efficiency Particulate Air (HEPA) filters, which are among the most effective filters available. You can also buy more efficient ÒmicrofiltrationÓ bags for most household vacuums.

An alternative to a portable vacuum is a central vacuum system, which makes it easy to keep your home clean. Because the central vacuum system can be exhausted to the outside, the dirty air and dust that are collected are not released back into the home. If you select a central vacuum system, make sure the system exhausts outdoors, not in the garage or basement, and the exhaust does not affect your use of the yard. An added advantage: central vacuum systems are very quiet.

Ask the Builder:

• What options do you have for a central vacuum system?
• How will the system be installed and exhausted?

Outdoors to Indoors:

Homeowners can unknowingly bring chemicals and other contaminants into their homes from the workplace, workshop, or yard. If you have an outside door leading to a laundry or mud room, consider using it as a changing room so you can avoid bringing contaminants into the home. Also use doormats or remove your shoes when you go inside. This is especially important right after you fertilize or use lawn chemicals. Pets may also track such chemicals indoors. (The use of lawn chemicals, especially pesticides, can be reduced in most homes by matching properly conditioned soils with plants that require fewer chemicals. Always follow the label during applications.)

Your windows may be your most effective line of defense against polluted outdoor air. Contaminants can come in through open windows, so remember to close them if outside activities like barbequing, mowing, fertilizing, or painting may affect the indoor air. If your windows are open during such activities, don't operate exhaust fans since they draw air into the home.

Maintaining the quality of your home's air isn't difficult, but it does take a good initial design and a certain attention to detail. By considering these issues during construction planning, you can help design and build a home that is healthy for years to come.
Whether your home is built tight or not, you can always improve your indoor air quality by reducing sources of common contaminants:

• Air fresheners, especially oil-based fresheners that plug into outlets, contain chemicals that may irritate some individuals. Asthmatics may suffer attacks in homes with air fresheners.
• Candles produce soot that accumulates on furnishings, ceilings, and in your lungs.
• New carpeting, paints, and varnishes, if not chosen properly, generate significant amounts of volatile organic compounds (VOCs) that can be toxic, so ask for low-VOC paints and other coatings. The Carpet and Rug Institute's (CRI) "Green Label" testing and labeling program identifies carpet products that are truly low-VOC.
• Cooking or bathing without ventilation can cause humidity levels to become unacceptably high, especially in newer, energy-efficient homes. This excess moisture can lead to mold and mildew.
• Gas stoves and ovens exhaust combustion gases directly into the home.
• Fireplaces, wood stoves, gas and oil furnaces, boilers, and water heaters are potential sources of combustion gases. Many high-efficiency furnaces and water heaters, known as "condensing" furnaces, draw air from - and vent directly to - the outside of the home, rather than using air from the utility room or basement. These furnaces protect the home from the release of combustion gases inside and help prevent "backdrafting" of fireplaces and other burners. Because these systems do not need to use a chimney or flue in the traditional sense, you may have more flexibility in locating the furnace.
• Household chemicals such as cleaners, solvents, and pesticides can contribute to poor indoor air quality. Read the handling and storage requirements on the label when purchasing such products, use them appropriately, and store them in a locked cabinet to protect children. Alternatively, opt for natural cleaning agents such as lemon juice and vinegar.
• Cars, gasoline, paint, and other chemicals you store in an attached garage generate toxic gases that can leak into your home. Garages should be well ventilated, preferably with an exhaust fan. If possible, store chemicals, fertilizers, and gasoline in an outside shed away from home entryways. In cold climates, take care to prevent chemicals and paints from freezing since they may be damaged and then require disposal.

1 The net cooling effect of a young, healthy tree is equivalent to ten room-size air conditioners operating 20 hours a day. 2 One acre of forest absorbs six tons of carbon dioxide and puts out four tons of oxygen. This is enough to meet the annual needs of 18 people. 3 There are about 60 to 200 million spaces along our city streets where trees could be planted. This translates to the potential to absorb 33 million more tons of CO2 every year, and save $4 billion in energy costs. 4 Healthy, mature trees add an average of 10 percent to a property's value. 5 In laboratory research, visual exposure to settings with trees has produced significant recovery from stress within five minutes, as indicated by changes in blood pressure and muscle tension. Join The National Arbor Day Foundation Today & Receive: 10 flowering trees: 2 Flowering Dogwoods 2 Flowering Crabapples 2 Goldenrain trees 2 Washington Hawthorns 2 American Redbuds, or other trees selected for your area. You’ll also receive the Foundation’s colorful bimonthly, Arbor Day, a membership card, and The Tree Book, with tree planting and care information. Your six to twelve-inch trees are guaranteed to grow or they’ll be replaced free of charge. Trees are shipped when conditions are right for planting in your area, February through May in the spring, or October through mid-December in the fall. To receive your free trees, send a $10 membership contribution to: 10 Flowering Trees The National Arbor Day Foundation 100 Arbor Ave., Nebraska City, NE 68410 or join online at arborday.org Join now, and plant your Trees for America!