Importance of What We Breathe
The pandemic changed the way we think about many things. One important change is that it forced us to think of the importance of consistent air exchange in our buildings.
We focused on air changes and bringing fresh air into closed places because of the way the virus spreads indoors. We realized with growing certainty that breathing the same air as everyone else inside the building puts us at higher risk. Moving forward I hope we continue to frown upon breathing in everyone else’s “speaking moistly”.
Why Choose An HRV/ERV?
Here is where a proper Heat Recovery Ventilator (HRV), or Energy Recovery Ventilator (ERV) system comes in.
HRVs and ERVs both deal with the same basic question – how do we get fresh air into the home? When heating costs were low not much thought was put into making sure the building was air tight. It didn’t matter, we simply burned more logs to stay warm in winters. Now we build homes as tight as possible. The goal is to reduce air flow through various building parts to zero. But this means that the home’s occupants breathe the same air over and over. Needless to say, this is not ideal. HRV’s and ERV’s work to make sure that you are in control of your air in your home, and that you get fresh air every day. They are a critical component of building a healthy home.
How Does an HRV/ERV Work?
HRVs and ERVs both exchange the stale inside air with fresh outside air. But instead of direct replacement the inside air is pushed through a core that pre-conditions the incoming air from outside. Practically how this works is that your 20 degree interior air is exhausted through small channels that intermingle with the channels bringing in the -20 incoming air. Now instead of -20 degree air coming in, it’s closer to 10 degrees when it gets dumped into your furnace return air, heated the rest of the way and sent throughout the house. Consequently, the fresh air the home requires costs very little to heat compared to opening a door or window.
But What’s The Difference Between an HRV & ERV?
The difference between an HRV and an ERV is that ERVs will also reclaim the energy from the moisture in the air. So in winter when it’s dry outside and properly humid inside, your ERV transfers the moisture that would otherwise have been lost to the outside to the dry air coming in. And, vice versa, in summer your ERV transfers the humid air coming from outside to the dryer indoor air on its way out. In contrast, an HRV will always move your indoor air humidity level closer to the exterior humidity level. So generally in winter it will dry your home, and in summer it will moisten your home.
Can You Eat Your Cake and Have it Too?
This is where the benefit of having both cores in an exchangeable unit like the vanee unit we spec in our builds. This gives a bit more control over humidity. For example, in a new build there’s a lot of latent moisture in all the building products. Generally it takes a good year to get all that humidity out, so having an HRV core in winter to bring dry air in, and an ERV core in summer to keep humid air out makes a lot of sense.
At the end of the day the important point is bringing in fresh oxygen. When homes are sealed as tight as our blower door tests are showing, it is imperative to have a source for bringing in fresh oxygen. HRV’s and ERV’s perform well as the lungs of the home to make sure you’re breathing in fresh air at home, and non-covid laden air in restaurants, Jets games, schools, and other public places. Make sure the spaces you spend lots of time in on a regular basis have mechanisms for providing clean air. Whether you are building a new home and the HRV is required by code, or you are doing a renovation and have the opportunity to add a unit, they are well worth the cost to ensure you have healthy air in your lungs!