DIY Network

Don't Forget About the "V" in HVAC

This energy recovery ventilator both pre-cools and dehumidifies the air before it's delivered into the home.

Sure, it's nice to open the windows and let in fresh air, but in the heat of summer or winter's frigid days, most of us choose to create a cozy environment inside our homes and keep the outside air out. Unfortunately, that means that air can get stale. If there are allergens or odors inside the home, they get trapped and have no way out. The good news is there's a way to have your fresh air and to be cozy as well. If you're having a home built, talk to your builder about having a ventilation system installed, since some builders don't automatically install ventilation systems.

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Ventilation (the second letter of HVAC) is an important component of the HVAC system, which also provides heating and cooling. To help keep the quality of the air inside your home fresh and clean, it's essential to draw in fresh air and push out stale air. Tightly sealing a home to prevent air inside the home from getting out, and outside air from getting in, is critical in keeping you comfortable inside the home, as well as keeping the home energy efficient. But in a tightly sealed home, if indoor pollutants can't get out they can compromise your health. In everyday living, we're exposed to a number of indoor air pollutants, including the following:

• Odors from cooking and other activities.

• Water vapor from cooking, bathing and breathing.

• Gasses called volatile organic compounds (VOCs), found in carpets and glues in cabinets, and other products made using organic chemicals.

• Vapor from cleaning products.

• Combustion byproducts from natural gas, propane and oil appliances -- and from wood-burning fireplaces.

One common way to introduce fresh air is through a direct ventilation system, where fresh air is forced into the air-handling unit (AHU) and distributed throughout the home. To exhaust stale air, fans are located in specific areas such as bathrooms and kitchens (known as local ventilation). These fans help to move moisture, humidity and odor out of the home. Exhausting moisture helps to protect the drywall and framing from the possibility of moisture damage. Be sure that local mechanical ventilation exhausts air directly to the exterior of the home. Models that simply diffuse air through the room or exhaust air behind your walls or above your ceilings don't remove pollutants and don't improve indoor air quality. In fact, moist air exhausted into wall or ceiling cavities can condense on framing members, lead to rot and eventually cause structural issues. It also can wet drywall and promote mold growth.

An alternate option to a direct ventilation system is a heat-recovery system. This type of ventilation pre-heats or pre-cools incoming air using outgoing air (hence, the "heat recovery" part of the term) depending on the season, which dramatically reduces the energy costs of ventilation. So, for example, it would pre-heat incoming air in winter and pre-cool it in summer. One type of heat recovery system that also dehumidifies the air is an energy recovery ventilator (ERV), which is beneficial in humid climates.

Unfortunately, a ventilation system isn't always a part of the HVAC system. We'll talk more about the features and benefits of ventilation in future articles, but remember: when your home is being designed, make sure you talk to your builder about your home's ventilation system and ask the following:

• Whether a ventilation system is being installed in your home and, if not, what additional costs would be incurred if you do choose to have one installed.

• What type of ventilation system is best for your climate location.

• Whether the kitchen and bath fans exhaust air to the outside of the home, and not somewhere within the home.

RESOURCES :

For more information on the topics contained within this article please reference The U.S. Department of Energy's (DOE's) Building America Program

The Building America program works with members of the home-building industry to produce quality homes that use less energy without costing more to build.

Website: www.eere.energy.gov/buildings/building_america/