Fixit: ERV would rid house of stale odor

Q Our house sometimes smells stale when we walk in at the end of the day. We were told that we need more ventilation. What exactly does that mean? Opening the windows is not always practical.

A Ventilation, exchanging indoor air with outdoor air, can be done by opening windows, but you'll pay an energy penalty for that. In addition, leaving windows open while you are gone can be unsafe and potentially damaging, depending on weather conditions.

A better long-term solution is to install a ventilation system, such as a high-efficiency exhaust fan in the bath (if furnace and water heater are the sealed-combustion type). These are very quiet and operate for long periods or continuously at low speed, pulling stale air out of the house. It's replaced by air from the outdoors that comes in naturally through gaps, cracks and spaces around doors, windows and other building components. The drawback to this type of ventilation is that the makeup air could come down a chimney or from an attached garage, bringing odors and fumes into the house.

An energy recovery ventilator (sometimes called an air-to-air heat exchanger, or ERV) solves this problem. A designated port controls the source of incoming air (another port handles outgoing air). ERVs ensure that the proper amount of fresh air is brought indoors in all seasons. They capture thermal energy, blunting the energy penalty, and transfer a high percentage of the water vapor to the airstream with the least amount of moisture. That means an ERV "kicks out" some of the incoming moisture in summer, keeping your home more comfortable, and retains some humidity in winter, again providing more comfort.

For a free publication on "Indoor Ventilation" from the Minnesota Energy Information Center, go to www.commerce. state.mn.us. Enter "indoor ventilation" in the search box. Or call 651-296-5175; elsewhere in Minnesota, call 1-800-657-3710.