Mechanical ventilation is the key to indoor air quality in green homes
While it's not as sexy as choosing granite countertops or fine hardwood floors, designing for proper indoor air quality can make a bigger impact on a home.
It's a surprising statistic, but data from the United States Environmental Protection Agency shows that indoor air can be two to five times more polluted than outdoor air, including the air in your home.
Ventilation design is vital to ensure the proper amount of air changes in a home and ensure control of moisture and pollutants to improve indoor air quality.
"Especially in new homes that are being built tighter and tighter, mechanical ventilation becomes a lot more important than it was in the past," said Jim Shelton, director of sales and marketing, Panasonic Eco Products Division.
Shelton said there are two types of ventilation found in a home:
Spot ventilation occurs to remove moisture from a location such as a bathroom.
Whole house continuous ventilation provides air exchanges to improve indoor air quality.
"In the past homes weren't as tight and air infiltrated into the house through cracks and seams," Shelton said. "You had fresh air coming into the house and were removing the moisture from the homes via spot ventilation in the bathrooms. Now with homes being built so tight, that's great from an energy-efficiency point of view but bad from an indoor- air-quality point of view."
Older homes may not have a bathroom fan installed at all, which may have met building codes at the time. However, that can lead to mold growth as well as damage to paint and other finishes.
Some homes may have the smallest fans available, which may meet code but does not provide adequate ventilation for moisture from a large bathroom or steamy showers.
Shelton said Panasonic's WhisperFit series of fans is aimed at the remodeling market.
"It's designed to easily retrofit those small commodity noisy fans and use existing ducts," he said.
Control options make the fans more useful. For instance, a motion control will operate the fan when someone enters the bathroom, and turn it off after a set time period when they leave.
A condensation control ensures the fan runs until the air meets a pre-set moisture limit then turns off.
"On the remodeling side, we see lot of need for good quality ventilation and if you have a nice quiet Energy Star rated fan and it's controlled properly so people will use it," Shelton said.
There are three basic ventilation strategies that a home can use to ensure fresh air exchange.
"It's bad to not have that air infiltration so you so you have to make sure you're using mechanical ventilation to bring in that fresh air," Shelton said.
Ventilation Air Only Shelton said this is a common approach because "It's an inexpensive way to do it." A speed-control equipped fan can run continuously in the bathroom, speeding up to extract moisture-laden air during a shower and running at a lower speed to exhaust air throughout the day.
"One fan can solve both problems," Shelton said.
Balanced Air Supply A balanced supply bringing in fresh air and exhausts stale air. These systems use a heat recovery ventilator (HRV) or an Energy Recovery Ventilator (ERV). Which one depends on the climate, Shelton said.
"The only difference is the ERV also addresses moisture whereas an HRV is only a heat exchanger," Shelton said.
A home could use a fan in a bathroom and an ERV or HRV to handle spot ventilation and whole-house ventilation.
Panasonic's WHISPERCOMFORT ERV is the first of its kind that can be ceiling mounted. Other ERVs are typically mounted in the ceiling, which makes maintenance more difficult. It uses two 4-inch ducts, one to exhaust stale air and the other to supply fresh air from outside.
The ERV runs at a low speed, which helps ensure that volatile organic compounds (VOCs) and other chemical and biological indoor air pollutants are vented out and replaced with fresh air.
This ceiling-mounted unit can be used as a spot ERV or whole-house ERV to comply with IAQ standards (such as ASHRAE 62.2).
Supply Air Another option is to supply fresh air ventilation through the HVAC system. The problems with that design are the fact that the large motor for the whole house fan is operating, and there's no ventilation of stale inside air, Shelton said.
Builders are learning the value of the balanced system to meet indoor air quality standards, and low-power fans with DC motors provide energy-efficient options.
"Consumers are doing research and going to builders demanding green homes," Shelton said. "And even national builders are making the move to green homes."
Read more about indoor air quality.
Gary Wollenhaupt is an experienced writer and editor, with a background as a daily newspaper reporter as well as corporate and agency public relations and marketing. He is constantly looking for affordable green upgrades to make to his home in eastern Kentucky.www