November 2025 EnergyWiseSM Tip: Clearing the Air
November 2025 EnergyWiseSM Tip: Clearing the Air
By: Energy Efficiency Program Manager Cory Fuehrer
In 2001, the Lawrence Berkeley National Laboratory published the results of the National Human Activity Pattern Survey. It revealed that, on average, Americans spend 87% of their time indoors and an additional 6% in enclosed vehicles. In 1800, 90% of Americans worked outside. 200 years later, less than 20% did. As more of our daily lives have been spent inside, the number of people with respiratory diseases, heart disease, certain types of cancer and/or other health problems has dramatically increased.
The U.S. Environmental Protection Agency (EPA) defines Indoor Air Quality (IAQ) as the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Understanding and controlling common pollutants indoors can help reduce the risk of indoor health concerns. While a great deal of energy can be used to purify indoor air, the EPA suggests three basic strategies to mitigate the problems while minimizing the impact on energy costs.
Source Control
Quite often, the most effective way to improve IAQ is to eliminate individual sources of pollution or to reduce their emissions. Some sources, like those that contain asbestos, can be sealed or enclosed. Others, like toxic and other byproducts from gas stoves or furnaces, can be adjusted or replaced to decrease the amount of emissions. Many activities such as cooking, painting, paint stripping, welding, soldering, or sanding can be taken outside or performed in a mechanically ventilated area. Smoking should never be done inside. Pets can be bathed to reduce their dander. Excess moisture in basements and other high humidity rooms can be managed with a dehumidifier, if necessary, to lower relative humidity to 50% or lower. In many cases, source control is also a more energy and cost-efficient approach to improving IAQ than increasing ventilation.
Ventilation
As long as the outside air is fairly pollutant-free, bringing fresh air into the home is an effective approach to lowering the concentrations of indoor air pollutants. However, ventilation often requires filtering, heating, cooling, dehumidifying or humidifying. Some homes, especially much older ones, are “leaky” and exchange plenty of indoor and outdoor air through gaps and cracks around foundations, windows siding and attics. But others, especially newer ones, tend to be sealed tightly and require additional ventilation. While opening a window and operating a ventilation fan is a simple way to bring in outside air, considerable energy use is necessary to make the air comfortable. For these homes, installing an energy recovery ventilator that replaces indoor stale air with fresh outdoor air while transferring heat into or out of the incoming air depending on the season is the most efficient and practical solution.
Air cleaning
Research shows that filtration can be an effective supplement to source control and ventilation. It turns out that 67% of U.S. homes already have a central heating, ventilation and air-conditioning (HVAC) system. If the system’s blower fan is powerful enough, a filter can be installed to create a highly effective whole house air purifier. Filters are rated on a Minimum Efficiency Reporting Value (MERV) scale that ranges from 1 to 20. The higher the number, the smaller the particles it
