HRV / ERV Efficiency

With our new Passive House building standard a key component of our green brownstone renovations are the ERV or HRV, or Energy Recovery Ventilator and Heat Recovery Ventilator.

Both units perform the same task of clearing the house of stale air and providing it with fresh air from the outside. In a “normal” brownstone this task happens naturally through all the cracks in the house. But with a green brownstone we have sealed all those cracks up in order to reduce the heat loss. So we need to compensate for the tight envelope by helping the house breathe.

Once the ERV is a key feature in any green brownstone renovation it becomes important what the energy efficiency of the unit is since it will be running a lot. There are several on the market. Here we have listed the best HRV / ERV’s for fan energy in the range of .5W/cfm, meaning they use half a Watt of electricity for every cubic foot of air moved each minute.

At this point in the technology 0.5W/cfm is considered a good industry standard.

The units that meet this standard are:
Sterling is $1900 list $1300 contractor cost plus shipping & tax with no accessories.
It has the highest heat transfer (because it is an ERV and recovers the latent energy from the moisture in the air).
It’s electrical efficiency is great on low speed, but sucks on high (over 1W/cfm).
The biggest problem is it’s a rotary wheel, so there is a high likelihood of failure. I have heard of it failing. And the wheel also has higher maintenance (maybe twice a year checks). Despite this I still have a soft spot for the Ultimate Air.

Some think this is the only unit that meets Passive House Standards, but they are confusing getting a product “certified” rather than the building as a whole (no HRV / ERV Required). You can install a unit that is PH certified and still not get your house certified due to other problems. But I think in a house that tight it’s a must have.

Sterling Ultimate Air Recouperator needs to be on low speed only.  It’s electrical efficiency is great on low speed, but sucks on high (over 1W/cfm).  The sterling has good specs and is very popular in Passive House building, and it costs similar to the Eko. So you have to see if spending $1000-1500 extra over others to save around 100-200 kWh/yr fits the project needs. It has the highest heat transfer (because it is an ERV and recovers the latent energy from the moisture in the air) and that is one of its pluses.

Lifebreath 155 & 195 ECM 2 speed (5 ranges to choose from)
Fantech SHV704 & VHR704, single speed
Venmar Eco 1.5 2 speed (5 ranges to choose from), around $1400
vanEE 90H-V single speed
Partners Choice HRV-210
Powermatic of Canada (Direct Air)

This list is without swiming over the ocean to Europe for the Passive House Certified units which are also excellent but more costly. For example the parts for the industry leader Zender are more than the installed cost for any of the above, including ducts & labor. Despite that there are several Passive House projects in Brooklyn where Zender units have been specified. Germany being the source of Passive House technology is still very much the source of our knowledge and materials.

About the author: Gennaro Brooks-Church

Leave a Reply

Your email address will not be published.