Though inactivity, smoking, and a lack of time spent in the great outdoors have all contributed to the staggering rise in asthma in past decades, some of the factors that contribute to asthma, which now affects an estimated 24.6 million Americans, may be aggravated by the way indoor air quality changes in green homes.
“Since the 1970s, asthma rates have tripled,” says Dr. Nathan Rabinovich, an asthma specialist at National Jewish Health. “It’s possible that we ended up increasing air pollution exposure because if you increase humidity then you increase house dust, mites, and mold. If you just do that, you may be getting into trouble. We have drastically changed how we’ve built homes. Energy-efficient homes causing sickness is a possibility I put forth.”
Energy-efficient homes became popular in an effort to save money, reduce emissions and conserve resources.
“Studies show that if you weatherize a home, your temperature and humidity go up, but also so do your allergens, like mold and dust,” Rabinovich says. “In green housing, if you do the insulation and make sure you have decent ventilation and fans where they are supposed to be, then that may balance it out. So just a word of caution: When you solve one problem you may create another one.”
The Environmental Protection Agency has confirmed that as homeowners work to save energy, ventilation systems are not bringing in enough outdoor air. Inadequate ventilation of a room can also occur when an air vent is blocked and outdoor air does not properly reach main areas like a living room. The EPA confirms that indoor allergens and irritants play a more significant role in triggering asthma attacks than outdoor allergens. Common triggers include cigarette smoke, pets, cooking smoke and molds.
But the rise in asthma cannot solely be attributed to indoor air quality.
“It depends on each environment, but Boulder isn’t Beijing, so pollution in the outside environment is not so much the issue,” says John Zhai, a professor in the University of Colorado Boulder’s civil, environmental, and architectural department.
Zhai says he agrees with Rabinovich that the correlation between new building techniques and asthma triggers is evident when looking at indoor contaminants, but the solution is not always as simple as opening or closing a window to let the bad stuff out.
“You don’t always want uncontrolled ventilation like an open window,” Zhai says. “You have to consider your surrounding environment. Are you in a rural area or an urban one? We did a study three years ago testing four buildings, two in Boulder and two in Denver. We focused on the type of particles concentrated inside and found that harmful particles coming from the outside were double the inside concentration.”
These particles mostly came from car emissions.
“In that case, we want a tight building, otherwise the contaminants will be sucked in through the windows,” Zhai says. “Tight” refers to how effectively a structure is sealed off.
Zhai and Rabinovich both said one guideline is to open a window when cooking, especially on a wood- burning stove. Contaminants generated from cooking, however, are more of an issue found in developing countries.
“There are a ton of factors that can explain lung health,” says Joe Collida, a home performance contractor and owner of Indoor Air Quality, Inc. “Materials, for instance, are important if you have a home that is truly tight. If people are concerned about the air they are breathing, a monitor can put a number to the dust. The house may need more mechanical ventilation.”
An EPA study concluded that modifying materials used to build energy-efficient homes could be a healthy and cost-effective fix.
Rabinovich says he thinks the solution will be multifaceted.
“We could really change things if we changed behavior,” he says. “We don’t focus on the environment enough because it is hard to convince people to change their behaviors. An effective approach will be a public health approach. How we are building homes, for example? How can we make foundations less prone to dampness? Things like this.”