Energy Recovery Ventilators work in much the same way as heat recovery ventilators (HRV). Warm air exits the home through a special ductwork and box. Cool outdoor air is brought in through another duct instead of gaps and cracks in the building. Ductwork for incoming and outgoing air are overlapped so that the heat from one duct will conduct across the metal and warm up the incoming air before it reaches the home. The air does not mix, so fresh air is not diluted, but incoming and outgoing air pass each other in special chambers that allow the exchange of heat energy. This reduces the energy required to heat the home by pre-warming incoming air before it must be further heated.
An energy recovery ventilator (ERV) goes a step further to transfer moisture from incoming to outgoing air, or vice versa, as needed. The choice between an HRV and an ERV depends on your climate and your household activity. If you find that your home is too dry in the winter, an ERV will maintain any humidity already in the home, while an HRV will make matters worse by venting moisture outside. In the opposite way, if your home is too humid in winter, an HRV will help you by removing excess moisture.
The energy recovery ventilator may cut out extra steps and save energy use by balancing incoming air’s temperature and moisture content instead of blindly dumping heat and moisture outdoors. While most publications talk about benefits in winter months while you are heating your home – they also work in the summer with no changes required. The system automatically handles the inverse: cold air that is being vented outside will cool down the incoming warm air from outside, thus reducing the effort needed to cool the new air!
Too long, didn’t read version: energy recovery ventilators save energy by tempering exhaust air with makeup air without mixing the air itself, as well as keeping humidity consistent.
-Marshall Tramp, CPI, RMP
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