It works like this: The ERV has two fans in the cabinet along with a heat exchanger and a desiccant. The outside air fan (1) draws air in from the outdoors; the Exhaust fan (2) draws air in from the home and the heat exchanger (3) heats or cools the incoming outside air while the desiccant removes humidity.
Okay, so what’s the benefit?
To help control indoor air pollutants and contamination it is essential to have fresh outside air. The problem with bringing in outside air is that it is either hot and humid or cold. If we didn’t pre-treat it we would need to upsize the HVAC equipment to handle the extra load; not a very good way to save money!
Since you have already spent the money to heat or cool the inside air we are going to use that to pre-treat the incoming outside air for temperature and the desiccant is going to remove the humidity.
Now for the details!
The ERV pictured above is in operation during the Heating season (Winter). Warm air (air that you have paid to heat) is piped in through normal exhaust locations like bathrooms and kitchens. This is air you are already exhausting to the outdoors with out recovering any of the energy used to heat it. IOW, every time you turn on an exhaust fan the air you have paid to heat or cool is just being wasted outdoors!
The ERV pulls in outside air through fan number 1. This cold outside air is directed through the heat exchanger along side the warm indoor air. The warm indoor air gives up some of its heat and warms the outside air; this newly warmed outside air is directed through a desiccant where humidity is greatly reduced and then it is piped directly into the return air of your central HVAC system!
The warm inside exhaust air and the outdoor air are never in direct contact with each other; so all the bad smells associated with bathroom and kitchen exhaust fans go outside where they belong but we “recover” some of the heat so it isn’t all wasted!
Fresh outdoor air is the single most important component to a healthy home; and an ERV is the most cost effective way to treat outside air.
During the Cooling season (Summer) the only difference is that the cool indoor air is used to cool the hot outdoor air. The airflow remains the same so there are no complicated mechanical systems to switch over or think about; in fact the only thing that needs regular maintenance are the filters.
As you can see the basics are very simple: