The U.S. Environmental Protection Agency (EPA) is inviting builders to adopt specifications for new homes that are “designed for improved indoor air quality compared to a home built to minimum code.” The EPA calls its new program Indoor AirPlus.
Builders who sign on to the program must adhere to Energy Star Homes requirements, as well as to a list of Indoor AirPlus specifications, many of which appear to have only a remote connection to indoor air quality (IAQ).
For example, the specifications require the installation of:
- Bituminous membrane at roof valleys;
- Pan flashing under all windows and doors; and
- Copper or stainless-steel screens installed at all openings that cannot be fully sealed (e.g., attic vents).
Most of the EPA’s specifications are sensible recommendations for builders interested in producing quality homes. But the program requirements are so specific that they raise an important question: do new homes with these details actually have better indoor air quality than homes without these details?
The answer: probably not. As it turns out, the EPA has no data to support a connection between the Indoor AirPlus specifications and indoor air quality.
The overwhelming factor is occupant behavior
There’s a dirty little secret undermining EPA’s new home specifications: the most important factor governing indoor air quality is occupant behavior, not construction details.
Here are some examples of things homeowners sometimes do:
- They smoke.
- They install and use humidifiers.
- They forget to operate exhaust fans.
- They bring home clothes that emit dry-cleaning chemicals like perchloroethylene.
- They spray pesticides indoors.
- They ignore routine cleaning and home maintenance chores.
Behaviors like these tend to overwhelm the IAQ effects (if any) of sill pan flashing or attic vent screening. Unfortunately, the EPA’s Indoor AirPlus program has fallen victim to a logical fallacy. The agency argues — correctly — that sill pan flashing can reduce the chance that water will enter a wall cavity. But the next logical leap is completely unwarranted: the conclusion that a home with sill pan flashing is a home “designed for improved indoor air quality compared to a home built to minimum code.”
Dragonflies and motorboats
Let’s compare indoor air quality to waves on a lake. The effect of sill pan flashing resembles that of a dragonfly skimming the water’s surface. The effect of occupant behavior, however, resembles that of a motorboat towing a water-skier. The Indoor AirPlus program wants to solve the wave problem by reducing the dragonfly population.
Actually, the EPA is aware of the effects of occupant behavior on indoor air quality. Unfortunately, however, that awareness was insufficient to kill the idea of the Indoor AirPlus program.
In an on online guide called The Inside Story: A Guide to Indoor Air Quality, the EPA notes, “Human activities can be significant sources of indoor air pollution.” Among the guide’s recommendations:
- “Keep the house clean. House dust mites, pollens, animal dander, and other allergy-causing agents can be reduced, although not eliminated, through regular cleaning.”
- “Keep exposure to perchloroethylene emissions from newly dry-cleaned materials to a minimum.”
- “According to a recent survey, 75 percent of U.S. households used at least one pesticide product indoors during the past year. … These products can be dangerous if not used properly. … It is illegal to use any pesticide in any manner inconsistent with the directions on its label.”
Unfortunately, the guide also includes bad advice: “Ventilate the attic and crawl spaces to prevent moisture build-up.” This EPA recommendation is directly contradicted by the agency’s own Indoor AirPlus program, which requires builders to “seal crawl space and basement perimeter walls to prevent outside air infiltration.”
A dearth of research
If adequate research funding existed, it would be interesting to build 100 new homes — half built to minimum code standards, and the other half following the Indoor AirPlus specifications. A year after the homes were occupied, it’s probable that researchers would either be unable to detect any measurable difference in IAQ between the two groups of houses, or that measurable differences would be easily traced to occupant behavior.
The person responsible for the Indoor AirPlus program is Sam Rashkin, the EPA’s national director for the Energy Star Homes program. As it turns out, Rashkin has a very accurate understanding of the weak link between new-home specifications and indoor air quality; however, Rashkin’s conclusions don’t appear on Indoor AirPlus brochures.
“There is no single study that definitively calculates IAQ metrics for homes with and without the complete IAQ package,” said Rashkin in a 2004 interview. “I don’t think it’s good tactics to try and define IAQ impacts. It’s far too contentious and easy to obfuscate by opposing interests.”
“You’d have to be insane”
Interviewed a year later, Rashkin elaborated on the same theme. “It’s important for builders not to make healthy-house claims, or to make claims of better air quality,” said Rashkin. “We can’t say there is a cause/effect relationship between these measures and indoor air quality. Of all the factors that can hurt indoor air quality, occupant behavior so dominates air quality conditions — there are so many things than an occupant can do to exacerbate poor air quality — that you would have to be insane to make claims that these homes have better air quality. All we are saying is that we are reducing the risk.”
Martin Holladay’s previous blog: “Toxic and Non-Toxic Houses.”