Energy recovery ventilators, heat recovery ventilators, and total recovery ventilators can play a large role in creating a safe and healthy home. These units improve the overall indoor air quality by bringing fresh air into the home.
When you bring fresh air into a building, that air must be either heated or cooled to the temperature of the inside.
Without a heat recovery ventilator, this can put an extra load on the furnace or air conditioner and therefore significantly raise your utility bills.
In areas where it is necessary to control humidity in the home, an energy recovery ventilator is used.
A heat recovery ventilator uses the air being exhausted from the home to preheat or cool the incoming air. These units are recommended for hot/dry climates. The system is usually activated by a timer control. In the typical system, the control starts and stops an intake and exhaust fan on a scheduled basis. The two different air streams pass through opposite sides of a heat exchanger where heat is transferred from the warmer air to the colder air. This fresh air is then distributed through a duct system to the home. Typically, the system uses the existing hvac system ducts.
An energy recovery ventilator is usually used in warm /humid areas where it is desired to lower the humidity of the incoming air as well as cold/dry areas where it is a priority to retain the moisture in the home. These units work in much the same way except the heat exchanger is replaced with a special membrane called a core. This core allows moisture to pass from one air stream to the other as well as the heat. This is necessary in warm/humid climates to minimize the increase in humidity during operation. The excess humidity would otherwise have to be removed by the homes' air conditioner. In cold/dry areas, the ERV is used to preserve the indoor moisture so that the operation of a humidifying system is minimized.
Total recovery ventilators combine both types into one unit. They are normally used in areas with cold winters and hot/humid summers.
The right type of unit for your home will depend on your location. They can be an independently ducted system, integrated into an existing ducted hvac system, or window/wall mounted units.
The units have a TOTAL RECOVERY EFFICIENCY (TRE) rating. This is a measure of the units' ability to save energy. The typical unit can recover 70-80% of the energy required to condition the incoming air. Some high efficiency units can recover over 90%.
When shopping for a unit it is important to get the proper size. They are typically sized to provide .35 air changes per hour. That means that for about every three hours of operation, the unit will completely replace the volume of air in the home.
To find the proper size you can multiply the square footage of the home by the ceiling height. Then divide your answer by 60. Finally, multiply that answer by .35 and you will have the unit size in cfm.
Once you have found the proper size unit, you can compare the brands to get the most value for your money. We have used our hvac service experience to compare the products and it is like taking a repairman with you while you shop.
They require monthly maintenance which includes filter cleaning. Also, each year, the core, condensate drain and pan should be cleaned.
Without proper cleaning, mold can grow in energy recovery ventilators. This can occur on the core as well as in the drain pain.
These units are expensive usually over $1000. It can take a long time to pay for them with energy savings. But, the added benefit of healthier indoor air makes them worthwhile.