If you’ve looked over the many services that we offer to homes to help them improve their indoor air quality, you may have noticed that we install and service heat and energy recovery ventilators in Woodbury, MN. Heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) provide similar benefits to homes through similar methods. In fact, they sound so similar that people are often curious if there’s any real difference between them. Is it maybe two names for the same device? And if there are differences, what are they and how will that affect the choice to purchase one?
HRV and ERV Basics
First, let’s run down what the two systems have in common. Both recover energy from a home’s exhaust air. This energy is then applied to an incoming current of fresh air to either pre-heat or pre-cool it. To put it another way, an HRV/ERV takes the air from inside your home and runs it through air from outside your home, allowing heat to move between them. The air that comes into your house is either cooled or warmed (depending on the season) before it reaches the living space. This lets you enjoy fresh air in your house without putting stress on the heater or air conditioner.
ERVs and HRVs have become popular in recent years because homes simply don’t “breathe” as well as they once did. To prevent heat loss and heat gain, homes have more powerful insulation. Although this helps make a home more energy efficient, it also can make it stuffy and filled with trapped contaminants. Putting in an HRV or ERV allows a home to breathe without suffering a plunge in energy efficiency.
The Difference between the Two
A heat recovery ventilator uses the heat in the stale exhaust air to pre-heat the incoming air. (In summer, the heat in the incoming air is lost to the cooler stale exhaust air.) The two currents of air don’t actually mix during the heat recovery process. The incoming and exhaust air pass through separate channels inside the HRV, and heat exchange occurs through conduction. The energy recovery rate is between 55% and 75%.
With an energy recovery ventilator, the system goes a bit further to also transfer humidity between the exhaust and incoming air, helping to balance indoor humidity levels around the year. The air currents actually do mix to allow for this moisture transference. An ERV tends to have higher efficiency than HRVs, although this depends on the humidity level. ERVs are better at raising indoor humidity than lowering it.
Which One Should You Have Installed?
The deciding factors for whether you should have an ERV or HRV for your house are specific to your home and local climate. An HRV is a better choice if you often have an overly humid house during winter, while an ERV is superior if your house is too dry. An HRV will tend to increase humidity during the summer, while an ERV will help control it. It is best to leave the job of making the choice to our indoor air quality professionals.