Air to Air Heat Exchangers

heat recovery ventilation schematicWe are living in a time when home energy costs are climbing at an unprecedented rate. Many home owners are looking for ways to reduce these costs by maximizing the efficiency of the heating and cooling systems that they already have in place. To increase efficiency, many homeowners are utilizing air to air heat exchangers.

An air-to-air heat exchanger is a small cabinet containing a core, two fans and some ductwork. It brings in fresh air from outside your house; during the winter it preheats the incoming air by transferring the heat from the stale air being passed to the outside. During the summer it preicools the fresh, incoming air stream. Air to air heat exchangers are also known as Heat Recovery Ventilators (HRV).

Stuffy Air

Modern homes are designed to conserve energy by sealing the indoor environment off as much as possible from the outside air. This maximizes your heating and cooling energy efficiency, but it also can cause health problems due to the lack of fresh air in your living space.

Humidity, dust and pollutants are trapped inside and the air can have a "stuffy" feel to it. Sure, you just open the window, but that would waste a lot of energy. An air to air heat exchanger can provide fresh clean air year round while helping you keep energy costs low.

Climate Check

The first issue that you need to address is whether or not this type of system could be applicable to the climate. Since the system operates by extracting the heat from the air that is in the exhaust from you home, it may not work well in extremely cold climates.

The air that is being drawn back into the exchange unit must be above freezing temperature, or else the humidity in the air will create ice in the system and block air flow. There are ways to combat this, such as piping the air underground at a depth that is below the frost line, but this can be expensive to create and troublesome to install in houses or buildings that are already constructed.

Is it Worth It?

One benefit of air to air heat exchangers is a decrease in how hard your central HVAC system has to work in order to heat the air that it is forcing into your home. Obviously, the more warm air that you can capture from your home’s exhaust the better.

The noticeable decrease in your heating costs will be determined by how much of this warm air you are able to recycle. In order to maximize efficiency, a large building or multi-zone home will require the installation of several smaller exchange units.

The initial investment required to get the system up and running properly can be substantial, but over a period of years, and by anticipating a continued rise in heating costs, you will see that the investment will slowly begin to pay for itself.


While the benefits are numerous from air to air heat exchangers that are designed and installed properly, the only real pitfall is the inability of the system to recover air at the proper temperature. In climates where severe sub-zero temperatures are prevalent, it may be better to consider an earth to air heat exchanger. This system offers the same benefits and functions in the same way; it just utilizes the heat from the ground in an effort to warm the recycled air from the homes exhaust.

Ultimately, the air to air heat exchange system is a great way to provide a constant flow of fresh air, add much needed humidity, and to help reduce the heating costs of your tightly weather sealed home. While it is not the answer for everyone, it is certainly an option that you should take the time to look into as you consider all of the options available to you.