If you own a newer home, it is likely equipped with an HRV or an ERV system. That is because these systems are crucial in maintaining in-home air quality. Nowadays, homes are built to meet high energy efficiency standards. They are constructed in an airtight manner, in order to keep conditioned air from leaking out of the house and unconditioned air from making its way into the house.
However, with such an airtight structure, how do we maintain safe, fresh interior air? That’s where HRV/ERV systems come in.
HRV stands for Heat Recovery Ventilator. This is a mechanism that expels stale air out of the home and brings fresh air into the home.
What makes this system unique is that it uses the heat from the outgoing exhaust air to heat up the incoming fresh air. By using the already existing heat from exhaust air, the HRV reduces the amount of energy needed to heat incoming air to the desired indoor temp. In other words, an HRV helps you save money on your heating bill!
Along their journeys through the HRV, the two air streams are sent through a ventilator core (labeled as 3 in the picture below). This is where their heat exchange occurs. The stale, outgoing air does not mix with the fresh air. On the contrary, both air streams remain in separate channels, and the heat transfer occurs through conduction.
ERV stands for Energy (or Enthalpy) Recovery Ventilator. It functions the same way as an HRV with one key difference. An HRV system only deals with heat transfer, while an ERV transfers both heat and humidity.
ERV units will generally be ideal in more extreme climates – such as tropical, humid climates or very cold, dry climates.
Let’s say you live in a tropical environment. As the energy recovery ventilator draws in the humid fresh air, it will extract the moisture and expel it into the outgoing, exhaust air. That way, when fresh air enters your home, it will not be uncomfortably humid.
Conversely, when it’s cold and dry outside, the ERV will extract the moisture from the stale exhaust air and add it to the incoming air.
Which Unit is Best For Me?
Before you decide on a unit type, you must first determine if you even need a ventilation system. Most all new houses are constructed to have an airtight building envelope and will need some type of ventilator.
The best way to measure the air leakage of your home is by conducting a blower door test. During this test, a specialist assembles a large fan on an exterior door and seals up all other openings. The fan will then pull air out of the home in order to determine its level of air leakage.
If the blower door results come back at 3 ACH (air changes per hour) or lower, then a ventilation system is recommended.
As stated above, the right unit will generally depend on climate. In some cases, it’s pretty clear-cut. For instance, if you’re living in the deep south with super humid conditions, an ERV is probably the right choice for you. And if you’re up in the cold, dry regions of northern Canada, go with an ERV.
However, in the central parts of the US, climates are a little milder, with less frequent extreme conditions. In these areas, it’s not necessarily crucial to have one or the other. It’s more on a case-to-case basis, and sometimes a matter of personal preference.
For instance, Colorado has a generally dry climate, so a lot of CO homes have humidifiers built into their HVAC systems. This negates the need for the humidifying features of an ERV.
It’s best to consult with your contractor or an HRV/ERV specialist to determine the right unit for you.
OK, I have an HRV. What Now?
How and When To Use It
If your house is equipped with an HRV or ERV, it’s always a great idea to familiarize yourself with the unit. Have a chat with the specialist who installed it and read over the user’s manual.
These systems vary from model to model, but their controls are all fairly similar. There will always be a master control panel like the one pictured below. This is where you can configure all of the operation parameters, such as cycle frequency or maximum relative humidity.
Your system will generally have to run multiple times every day. You can usually set it on an intermittent, recurring schedule. For instance, you may want it to kick on for 20 minutes every hour.
Make sure to get in the habit of running the system each time a shower or bath is used. It is recommended to run the HRV (or ERV) for its maximum time (which is usually 60 minutes) to make sure all moisture has been removed.
Another common setting is the maximum relative humidity (often abbreviated as RH) setting. This is a handy feature when you want to make sure it doesn’t get too humid in your house. Just set the control panel to your preferred relative humidity. When the system detects the indoor relative humidity exceeding this limit, it will automatically start to run in order to expel the interior air and mitigate humidity levels.
Routine maintenance is an important way to ensure efficient performance and longevity – plus it’s super easy!
Make sure to reference your user’s manual to find out when and how to clean the unit, as this process varies slightly with each model. But again, they are all fairly similar; so maintenance procedures will generally be along these lines:
The ventilator’s filters will need to be removed approximately every 2-3 months. Rinse these off with water and allow them to air dry.
The ventilator core should be rinsed out with clean water. This should occur about every 6 months.
Make sure to wipe out the HRV unit every time you access it, as significant amounts of dust and debris can build up over time.
Heat (or energy) recovery systems are, indeed, a very important component of the home. So it goes without saying that proper use and maintenance are crucial in ensuring that you have fresh, healthy in-home air year round.
At Scott Home Inspection, it is our number one mission to help Colorado families live in safe, healthy, and comfortable homes. Being that ventilation systems are such a vital aspect of new homes, HRV and ERV inspections are part of our standard inspections.
Our inspectors will closely examine these units, checking to see that they are in good condition and functioning properly. If an inspector notes any defects or anomalies, they will be sure to call it out in the report for further evaluation.
Chris Kimmel worked as an Associate Home Inspector for two years, handling numerous services including sewer scope inspections, pest inspections, mold air sample testing, radon testing, and water quality testing. Chris now works with Scott Home Inspection as a Content Writing Specialist.