If you've ever heard that the air inside your home is more contaminated than the outside air, it's true!
Today's buildings are built more air-tight tight than ever before and great care is taken to prevent air from leaking in or out.
Such tightly enveloped buildings are designed with the intention of keeping as much conditioned air inside as possible in order to save energy while reducing heating and cooling costs.
This technique, though, has some unintended negative consequences. While drafts are typically thought of as unwanted, indoor air quality can suffer from a lack of air exchange.
Nobody likes to breathe in old, stale air and without proper ventilation, humidity and other airborne pollutants can build up and damage your property and your health. Luckily, there are several solutions to this problem.
The Old-Fashioned Way
Sure, the simplest way to increase ventilation is to open a window or door. As air is sent out through one window, the negative pressure brings in a fresh breeze through the other window.
However, unless the temperature and humidity levels are just right outside, this isn't the best option. Not only will will the incoming air be too warm or cold for your own comfort, you’ll be wasting money heating or cooling your indoor air, which is swiftly being sent outside. Also, because you have little control over what air is coming in or leaving through these openings, you may not be exhausting the pollutants from inside your home, and might even be introducing new contaminants from outdoors along with pesky insects!
The New Way
A great solution to all of these problems is using a heat recovery ventilator (HRV) or an energy recovery ventilator (ERV). Both ERV and HRV ventilators can provide the same principal function, but ERV’s can have additional benefits when they are installed in certain climates.
At a basic level, the purpose of either system is to provide fresh outside air while exhausting stale indoor air. As we mentioned previously, introducing fresh air could affect the comfort of your home and increase your heating and cooling costs. The main benefit to using an HRV or ERV is that it transfers much of the heat from one air stream to the other.
This means that in the winter, your hot, stale, indoor air is being used to preheat the fresh, cold air from outdoors. With the incoming air now much warmer than it began, you will use much less energy conditioning it once it gets inside. During the summer, the cold air from indoors steals heat from the incoming, hot air, cooling it, and reducing the cost of cooling your home to a comfortable level.
How ERVs and HRVs Work
The physics behind ERVs and HRVs is related to the second law of thermodynamics, which generally states that energy will spontaneously move from areas of high energy to areas of lower energy.
What we know as temperature is actually a measure of the average kinetic energy of molecules of a substance. Therefore, when two substances with two different temperatures meet, energy (i.e. heat) is transferred from the high temperature substance to the low temperature substance.
The transfer of energy is never complete, but if given enough time, heat will be transferred to the lower temperature substance until the two have equal temperatures (think about mixing one cup of hot water and one cup of cold water to make two cups of warm water).
In HRVs, two sources of air are brought into the system with different initial temperatures. Let’s talk about when the outdoor air is cold and the indoor air is relatively warm (especially when being heated).