For those homeowners in pursuit of a highly energy efficient home, a well-sealed house can create its own challenges. However, proactive ventilation is essential to maintaining healthy indoor air quality. Indoor air quality can be affected by a broad range of contaminants, some that can be avoided, others that need special remediation.
Types of Contaminants
- Biologic — This can be anything created by living things. Mold, bacteria, pollen, viruses, animal dander and waste from dust mites and cockroaches. These elements can cause allergic or asthma reactions, illness and other discomfort.
- Combustible pollutants — The ash, dust, and gasses caused by burning fuel for heat, domestic hot water and cooking, including tobacco smoke. Carbon monoxide, nitrogen dioxide and other gasses can be dangerous and potentially deadly if not vented properly. Particulate matter (smoke, ash, and dust) can also trigger asthma and other respiratory illnesses.
- Formaldehyde — Used in numerous common household items, including fabric, carpets, upholstery, particleboard and plywood paneling. Formaldehyde can cause eye and respiratory irritation, coughs and skin rashes.
- Radon — A naturally occurring radioactive gas element, radon can seep into homes through basement foundations and crawlspaces, and is a known carcinogen. Most states where radon is prevalent require testing for residential properties. The EPA recommends testing for radon based on certain zones, which can be identified here. If radon is common in your area, you may want to specify some conduit for a basement mitigation system to save on the costs of a retrofit should radon be an issue once the home is built.
The good news is that most of these indoor pollutants can be reduced, mitigated or eliminated via appropriate and well-designed mechanical ventilation. In the case of tobacco smoke and formaldehyde, exposure can be limited by opting not to bring these products into the home. There are many products available that are formaldehyde free and eliminate the worries that off-gassing can cause.
We spoke with Frank Gioffre, owner of Healthy Homes with Energy Solutions, Clinton Me., and a member of the Maine Air Quality Council, about what he sees as the biggest challenges for air quality in homes. “Moisture is the number one source (after its human occupants) for problems with indoor air quality in a modern, tightly sealed home,” he said. “And the missing piece of the energy efficiency puzzle is effective mechanical ventilation.”
Most newer homes are now equipped with heat- or energy recovery ventilation exchangers. These provide fresh conditioned air and exhaust moist or contaminated air without losing the heat or energy to condition it. They are sized based on the cubic feet per minute (CFM) that is exchanged over time.
Your HVAC contractor can assess the specific needs for your home, but Gioffre recommends sizing a fresh air intake system based on the following basic measurements: 30 CFM for a great room, 20 CFM for a master bedroom and 20 CFM per person per bedroom.
Rooms that are subject to high moisture or other contaminants—kitchens and bathrooms with showers and tubs—need specific amounts for exhaust to balance the intake flow and remove the excess moisture produced in these rooms. Kitchens should be sized for 60 CFM, while basement areas and bathrooms should get 20 CFM capacity.
“In general, once I’ve worked through the configuration, I try to size slightly bigger to accommodate those times when extra people are in the house,” Gioffre noted. He explained that the increased ventilation is only incrementally more expensive when sizing for a house.
The benefits of improved air quality through heat recovery ventilation in reduced medical costs alone may recoup the initial investment in the first year and certainly adds to the value of the home.