Energy Efficient Homes: Indoor Air Quality and Energy1
Quick Facts
Indoor air quality influences occupant health.
Some pollutants found in homes come from outside, but many indoor air pollutants are a result of volatile compounds produced inside by the structure itself, paint, carpet, furnishings, and many other sources.
Improper natural ventilation practices can worsen the indoor air quality problems and increase a home's energy consumption.
A properly designed energy efficient home can help you manage your home's indoor air quality.
Isn't indoor air healthier than outdoor air?
Many believe that the indoor air of typical homes is cleaner and healthier than outdoor air. And, many of us may presume that if we keep polluted outdoor air from coming into our homes we'll be able to maintain clean indoor air.
Unfortunately, this is not necessarily true. The U.S. Environmental Protection Agency (EPA, 2008) indicates that indoor air can actually be more polluted than outdoor air. This is because while some pollutants may come from outside, many of our indoor air pollutants are produced inside the home. These pollutants can come from your home's structure, paint, carpet, furnishings, or many other sources inside the home. To make things worse, if you fail to bring in enough outdoor air to dilute the level of indoor pollutants, and to take those pollutants outside, they can accumulate to levels high enough to cause health and comfort issues for the occupants.
Should I frequently ventilate the inside of my home to improve indoor air quality?
No, not frequently. Except for a few weeks of winter, outdoor weather is hot and humid almost year long in most areas of Florida. If you bring in the hot and humid outdoor air through frequent ventilation, it will raise your conditioned interior temperature and also increase indoor humidity. This can cause other indoor environmental quality problems such as mold, and it will increase your energy bill.
Do energy efficient homes have poorer indoor air quality?
Not necessarily. You can achieve both energy efficiency and healthy indoor air quality through (1) properly designed building construction and technologies, and (2) proper home maintenance practices.
In the 1970s, the world experienced a major energy crisis. Energy prices increased dramatically and energy savings became a critical factor of housing affordability for most families in the United States. Since then, people have focused on developing building structures and systems to maximize energy conservation. Now (2008) individuals are even more motivated to conserve energy due to soaring energy costs.
As a result, building structures have become tighter, which means there are less air exchanges between indoor and outdoor spaces. In Florida, conditioned air provided by heating or cooling equipment should be kept inside the building while unconditioned outdoor air intrusions should largely be kept from entering the building.
While energy savings have been a major concern for decades, it wasn't until the 1990s when many researchers started paying attention to its impact on human health, and only in the past several years have builders and homeowners followed suit. Because of that, some people still incorrectly assume that energy-conserving or "energy-tight" homes are more susceptible to indoor air pollution than less energy efficient homes. These people may be surprised to learn that, when properly designed and maintained, energy efficient homes may have better indoor air quality than leaky, drafty homes.
Simply put, new, energy efficient homes, and older homes that have had energy conservation features correctly installed, do not allow as many pollutants to permeate the home in the first place. Effective, properly designed heating, ventilation, and air conditioning systems, bathroom and kitchen exhaust fans, and a tight building shell not only remove excessive moisture and cooking odors in the building, but also such measures can ensure that most outdoor pollutants do not enter the home in the first place. Pollutants that do enter can be removed with controlled ventilation. Remember, in a drafty, inefficient home, there is no way to control the air that enters through cracks and other openings. That air flow is affected by wind speed, topography, vegetation, and many other factors.
When is the right time for natural ventilation?
To discourage mold growth while promoting energy efficiency, it is recommended to keep indoor relative humidity below 70% (ideally between 45% and 60%), and indoor temperature no higher than 68°F in the winter and no lower than 78°F in the summer. When natural ventilation is needed, you can use indoor and outdoor humidity and temperature monitors to judge if it is the right time to do so. If the difference between indoor and outdoor levels is extreme, you may consider another time. Also, keep monitoring indoor relative humidity and temperature levels during natural ventilation and stop when they go over the levels recommended. During times of high humidity, especially during rainstorms, the air conditioner often does not run long enough to adequately control the indoor relative humidity. However, even if the relative humidity goes higher than 70%, this doesn't present a problem as long as the relative humidity doesn't stay that way for an extended period of time.
Do you have any additional tips?
Along with reducing energy costs it is important to keep in mind the health of you and your household. Do not compromise your health for immediate money savings.
Here are some basic tips to control the quality of your home's indoor air and protect your household from many airborne irritants and/or health problems:
Seal up any air leaks.
Keep your home dry (indoor relative humidity below 70%—ideally between 45% and 60%.
Keep your home clean and free from bugs and excessive dust.
If you use pesticides, do so only as directed in the instructions on the product labels.
When building new or conducting home improvement projects, choose products that have no or little potential health impact (e.g., little to no off-gassing of VOCs [volatile organic compounds], no formaldehyde, etc.)
Replace your heating and cooling filters regularly with good quality single-use filters designed for your system. If you have additional concerns about specific allergens, consult with your air conditioning contractor about filtration options more appropriate to your situation.
Use biodegradable cleaning supplies that do not off-gas.
If you have an attached garage or a fuel-fired appliance, heater or fireplace, install carbon monoxide alarms as recommended by the EPA or the manufacturer. (“Fuel-fired” means a device that uses kerosene, propane, oil, natural gas, or wood.)
Do not allow smoking inside your home.
Install smoke alarms.
Resources
U.S. Department of Housing and Urban Development. (2006). Help yourself to a healthy home: Protect your children's health. Washington, D.C.: U.S. Department of Housing and Urban Development.
U.S. Environmental Protection Agency. (2008). An introduction to indoor air quality (IAQ). Retrieved June 17, 2008, from http://www.epa.gov/iaq/ia-intro.html .
Footnotes
This document is FCS3275, one of an Energy Efficient Homes series of the Department of Family, Youth and Community Sciences, Florida Cooperative Extension Service, IFAS, University of Florida. This material was prepared with the support of the Department of Environmental Protection, Florida Energy Office. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the Florida Department of Environmental Protection. Original publication date: June 2008. Please visit the EDIS Web site http://edis.ifas.ufl.edu.
Hyun-Jeong Lee, assistant professor, Department of Family, Youth and Community Sciences; Kathleen C. Ruppert, associate Extension scientist, Program for Resource Efficient Communities; and, Wendell A. Porter, lecturer and P.E., Department of Agricultural and Biological Engineering; University of Florida, Gainesville, FL 32611.
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For more information on obtaining other extension publications,
contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative
Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
