Dear Jim: I have tried to make my home more airtight to cut my utility bills, but the indoor air sometimes seems stale and musty. What is the best way to get some fresh air without increasing my utility bills? – Michael H.

Dear Michael: Using caulk and weather stripping and installing new windows and doors can lower your utility bills considerably. The energy improvements also reduce the amount of fresh air entering your home. The most inexpensive method to improve the indoor air quality is to open a couple of windows for a few minutes several times a day when the air seems stale. This will not lose a great amount of heat energy because the heat content of air is low and the house will not cool much.

Also, try to reduce the amount of chemicals and cleaners you use indoors. Another simple method is to install a damper that brings fresh outdoor air into the furnace return duct. There are various methods to control how much fresh air is drawn in. The most effective method uses a controller, which allows you to adjust when and how long the damper is open.

When the outdoor air is excessively cold, hot or humid, the damper stays closed. The best method to bring in fresh outdoor air efficiently year-round is with an ERV (energy recovery ventilation) system. These systems bring in fresh outdoor air and exhaust stale indoor air at rates that you can control. The running time can be operated automatically from a timer, humidity sensors, carbon dioxide sensors, etc.

What makes these units so efficient is they capture heat from the outgoing stale air and transfer it to the incoming fresh air. The reverse is true during summer. If you would try to bring in this much fresh air without an ERV system, your utility bills would increase significantly.

In a typical home, the indoor stale air inlets are located in the kitchen and bathrooms. The fresh air outlets are in the living room or hallways. These systems generally have their own duct systems separate from the furnace.

The blowers and heat exchanger are located in the main power unit. The most effective type of ERV uses a special enthalpic heat exchanger design and materials, which also exchange moisture content along with the heat. This is often most beneficial during the summer. In many climates, the hot outdoor air is also humid, so the enthalpic heat exchanger removes the moisture before the fresh air enters the home.

The best ERVs have filters to clean allergens from the incoming fresh air. They also use variable-speed ECM (electrically commutated) motors. These motors are expensive, but they provide the most precise speed control and consume less electricity. This allows the system to control the air pressure inside the home for the best ventilation and indoor air quality.

The following companies offer heat recovery ventilators: Aprilaire, (888) 257-8801, www.aprilaire.com; Broan, (800) 558-1711, www.broan.com; Fantech, (800) 747-1762, www.fantech-us.com; Renewaire, (800) 627-4499, www.renewaire.com; and UltimateAir, (800) 535-3448, www.ultimateair.com.

Dear Jim: I am having a new heating and central air conditioning system installed. The contractor is trying to sell me a cheap SEER-11 air conditioner. Isn’t this illegal with the new efficiency standards? -Sally F.

Dear Sally: The new energy regulations do not allow manufacturers to produce central air conditioners with efficiencies less than SEER-13 after Jan. 23, 2006. They can still sell what they have in inventory. If you do not air-condition often, it may make sense to buy an older model with lower efficiency. It will cost less initially, and if it is not often run, it will not significantly impact your utility bills or the environment.

Send inquiries to James Dulley, Bangor Daily News, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.