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Heat Recovery Ventilator (HRV) Buying Guide |
 Did you know that your home's indoor air may be more polluted than Los Angeles on a smoggy day? Cigarette smoke, dust, soot, bacteria, molds, carbon monoxide, formaldehyde, radon, pesticides, and vapors from scores of household cleansers and building materials are just some of the contaminants that may be tainting your home's air. "Sufficient evidence exists to conclude that indoor air pollution represents a major portion of the public's exposure to air pollution," states a report issued by the Environmental Protection Agency.
Indoors, air pollutants get trapped and build up, particularly in today's air-tight, super-insulated houses. When pollutants accumulate, some concentrations can exceed 100 times outdoor levels.
High indoor humidity can be a serious problem, too. Humid air encourages mold, mildew, and bacterial growth. In the winter, condensation collects on windows and can damage paint, insulation, roofs, and exterior walls. And in the summer, high humidity feels uncomfortable and strains air conditioning.
Aside from removing the source of the problem, the best way to keep a house from building up toxins and humidity is to provide plenty of ventilation. But how can you ventilate a house without letting costly heated or cooled air out the window? Meet the heat-recovery ventilator.
A heat-recovery ventilator (HRV), sometimes called an air-to-air heat exchanger is different than conventional vents and fans. With standard ventilation, air circulates through static, open vents or is expelled by fans, such as those used in bathrooms, kitchens, and attics. When room air escapes or is expelled, the energy that was used to heat or cool it is wasted.
An HRV can save 75% or more of that wasted energy. As it pushes out stale air, it pulls in fresh air, and—with little or no mixing of the two air streams—it transfers the heat or chill from the outgoing air to the incoming supply. The fresh air arrives pre-heated or pre-cooled and, with some units, pre-humidified or dehumidified.
Some HRVs mount like a room air conditioner in a window or wall opening` these are meant to handle individual rooms that have ventilation problems: bathrooms, laundry rooms, artist's studios, and darkrooms, for example. Larger, whole-house HRVs provide fresh air for all rooms. They often require routing ductwork to several places: to rooms where you want to exhaust stale air, particularly bathrooms, laundry rooms, and kitchens; to the outdoors; and often to the central heating and air-conditioning system's return air supply.
Though whole-house systems are installed primarily in new houses, they can be retrofitted into some houses that have good access for ductwork, particularly those with unfinished basements. To simplify installation, some systems can take advantage of existing ductwork—they're piped into the return-air system.
The cost of a ducted, whole-house HRV depends on the specific model, the amount of ductwork and accessory material needed, and the difficulty of installation. The units alone range from a low of $400 to about $1,500; most run from $500 to $900. The only way to estimate the total cost with installation is to get bids from air-conditioning contractors.
Mounted, room-sized models run from $350 to $450. Find out from your utility company whether or not they offer rebates for installing HRVs; some do. The amount of energy needed to run an HRV varies widely from one model to another and depends on the capacity of the unit.
A variety of sizes are available. Carrier, for example, makes 18 different models ranging in capacity from 150 to 1,270 cubic feet per minute (cfm). The right size to buy depends on the number of occupants and the cubic capacity of the rooms or house you wish to ventilate. For complete ventilation, the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) recommends replacing indoor air with at least 15 cfm per occupant. Sizes and lengths of ductwork runs can affect efficiency, so it's important to work with a contractor when planning a system.
Copyright. All rights reserved.
Photo courtesy of Honeywell
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