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Musings of an Energy Nerd

The EPA’s Indoor AirPlus Program

Will these features really improve indoor air quality?

Evidence is lacking to support the EPA claim that “homes with the Indoor airPLUS label are designed for improved indoor air quality compared to a home built to minimum code.”
Image Credit: U.S. Environmental Protection Agency

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:

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.

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:

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.”

Let’s compare indoor air quality to waves on a lake. The effect of sill pan flashing resembles that of a…

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