Jenny Blair
To save money on heating and cooling your home, air sealing is important. Every house has leaks and cracks through which a lot of air flows in and out. That can force your heating or air conditioning to work harder and waste money. Sealing those up as part of weatherizing your house can lower energy bills, particularly in leaky old houses. It can also help control humidity, which can in turn prevent mildew and mold.
“Good air sealing helps control the temperature, control humidity/moisture, and indoor air quality,” Matthew Smith, public relations manager of Efficiency Vermont, wrote to The Bridge in an email.
But plenty of things can foul house air, including combustion products from stoves, cleaning products, viruses, dander, gasses released by furniture, and so on. In a tight house, such pollutants may build up.
When it comes to improving indoor air quality, the three key strategies are removing pollution sources, cleaning the air with filters, and increasing the amount of outdoor air entering a house (ventilation), according to the Environmental Protection Agency.
Ventilation can happen in several ways. In houses with traditional forced-air heating and air conditioning — neither of which typically brings in outdoor air — fresh air enters through open doors and windows (natural ventilation) or cracks in the building (infiltration).
While the EPA recommends techniques for natural ventilation, such as opening windows to get a cross-breeze, it also warns that uncontrolled ventilation with outdoor air can allow contaminants in the air to bypass filters, plus bring in too much humidity.
There’s a third way: mechanical ventilation, such as through the outdoor air intake of a heating, ventilation, and air conditioning (HVAC) system.
Heat pumps, Smith explained, are all-electric, zero-emissions systems that also work as air conditioners and can reduce indoor humidity. Filters in the heat pumps remove harmful materials such as mold, allergens, and pathogens (such as viruses) from the air, he noted. Heat pumps can be added to almost any room or can use existing ductwork to replace, say, an oil furnace, Smith added.
The Bridge asked Efficiency Vermont about navigating the balance between a tight house and good air quality.
Controlled mechanical ventilation is the only effective way to introduce outdoor air, according to Li Ling Young, a lead engineer with Efficiency Vermont.
“Uncontrolled leakage is sometimes too much, resulting in overly dry or overly humid indoor air. And sometimes it’s too little, failing to adequately dilute pollutants,” she said. “In the past we have lived in leaky buildings that have relied on that leakiness to introduce outdoor air, but that doesn’t mean these older, leakier homes have been healthy. It’s faulty to believe a leaky building is going to result in good indoor air.”
Instead, Young advised setting up a “controllable environment,” minimizing or removing pollution sources within, then being deliberate about how much, when, and where outdoor air comes in — plus filtering and heating or cooling that air.
Efficiency Vermont can help Vermonters address air quality concerns as they navigate air sealing and ventilation, she added. The organization also offers free virtual home walkthroughs from energy consultants, weatherization rebates, and heat pump rebates, Smith noted.
For example, low-income Vermonters can get 90% of weatherization project costs back up to a total of $9500. Zero percent financing is available for some customers. The organization updates its income thresholds every year by county. Efficiency Vermont also offers incentives to businesses for custom energy efficiency projects.
“We’re very lucky that Efficiency Vermont’s programs are funded by ratepayers, so we are not affected by what’s happening at the federal level, “ Smith said. “Even at a time when other supports are kind of falling away, Efficiency Vermont is still here.”
