Tightening a home’s building envelope can result in significant energy savings, but it can also choke off the air exchanged through the building shell, potentially contributing to the buildup of indoor air pollutants such as radon, dust mite feces, and volatile organic compounds (VOCs). A conscientious builder would address this potential concern as a basic quality control requirement. But knowing what to do to improve indoor air quality (IAQ) and prevent indoor air pollution requires a basic understanding of chemistry and a specific set of construction practices.

IAQ Basics

Improving IAQ requires a systems approach. Scattered tactics that target a few isolated components, such as specifying low-VOC paints, will not solve indoor air problems alone, and may even miss the mark entirely for some consumers. This is why the U.S. Environmental Protection Agency (EPA) responded to consumer demand for healthier homes by developing the comprehensive Indoor airPLUS label for new homes as a sister program to its Energy Star for Homes program. To achieve the Indoor airPLUS label, a builder must first qualify the home to Energy Star standards and then layer in more than 30 additional home design and construction features to help better protect a home from indoor air quality problems.

The prescriptive directions of Indoor airPLUS focus on seven general categories: moisture control, radon mitigation, pest management, HVAC best practices with whole house ventilation, proper combustion venting, specifying building materials with reduced chemical off-gassing potential, and home commissioning. Laureen Burton, a toxicologist and chemist for the EPA’s Office of Radiation and Indoor Air, describes the approach as a balance between proper ventilation and source control.

Moisture is one source of indoor air contamination, according to Burton. Controlling moisture helps moderate the development of many pollutants, from dust mites to mold.

Radon is another source of concern; the odorless and invisible gas is the only pollutant for which testing is required under Indoor airPLUS. Other indoor contaminants have no standards or regulated residential indoor air levels against which to check a building’s compliance. But as a general rule, builders should try to minimize exposure to potential sources of indoor air pollution by choosing the least hazardous products that are still effective for the job. For example, you will likely paint every wall in your project, so use low-VOC paint to reduce harmful emissions as part of your approach to addressing IAQ (but not as the sole effort). In conjunction, for floor sheathing and carpet selection, specify materials that minimize the risk of moisture damage and offer reduced levels of harmful chemical content.

Burton also stressed the importance of layering: It’s self defeating to install a high-quality, ultralow-VOC carpet over a low-quality, potentially high-off-gassing pad. It’s also important to properly ventilate a newly finished interior prior to occupancy, and then to continue ventilating the home at the highest practical rate for several months thereafter.

Special IAQ Concerns

As the technical director of the Indoor Air Quality Association and president at Indoor Sciences, Ian Cull is often called to troubleshoot and recommend repairs for intractable IAQ problems, even after all of the basic best practices are in place. The EPA approach will work for the majority of consumers, Cull says, but a second category of people exist: the hypersensitive. “They have sensitivity to low concentrations of pollutants. You may follow all the EPA guidelines to the T and these people may still not find the place inhabitable,” Cull says.

While no reliable estimates are available, some experts claim that nearly 20 percent of the population have higher-than-average chemical or allergen sensitivities. Builders promoting improved IAQ will likely attract highly sensitive clients hoping to find relief, but their job then becomes tricky.

To start, people have two different sensitivities, Cull explains: chemical sensitivity and heightened sensitivity to allergens. Low-VOC carpets won’t help those with dust allergies, and those with high chemical sensitivities may still react to low-VOC paint.

For a person with high sensitivity to dust—which indicates an allergy to dust mite feces—a builder would be wise to recommend hard surface flooring, a central vacuum system, and an HVAC system commissioned to maintain the relative humidity below 50 percent, Cull says. For a person with heightened chemical sensitivities, a builder should know that most low-VOC paints are tested only in their white base. As soon as tint is added, the profile changes and the paint may now contain sufficient VOCs to trigger an adverse reaction in a highly chemically sensitive individual. Here, Cull recommends products tested under the Greenguard Environmental Institute label, which are tested for post-installation emissions; Green Seal, meanwhile, certifies products based on their VOC content. It’s ultimately the emissions that matter.

When working with sensitive clients, a builder must first understand what type of sensitivity exists: Is it pollen, dust mites, pet allergies, or chemical sensitivities? Which specific chemicals trigger a reaction? The strategies differ with each element. It’s not realistic for builders to know what to do in every case, so it’s wise to involve an IAQ consultant.

Unfortunately, qualifications for IAQ experts are difficult to ascertain. A consultant’s pedigree can range from a home inspector with a one-day class to a toxicologist with a Ph.D. You can refer to a professional association, such as the Indoor Air Quality Association or the American Industrial Hygiene Association, but you’ll still have to do your due diligence. Cull recommends starting the screening process by asking the consultant about their background in the specific issue on the table. “It’s challenging to connect with the right person, but if you seek expert advice and issues come up later, it’s not you or the designer that has frontline responsibility, but the consultant representing themselves as expert,” Cull says.