HRV/ERV Question

jb9

Hello,

I understand the concept being an HRV and ERV, but I don't understand what the penetration to a building envelope looks like in practice. I can't find any pictures online. Can it come in below a rim joist? Is it a vent higher on a building facade? I am designing a 2 story house but the 2nd floor will not have a floor chase so I am trying to figure out how the intakes will work. 2nd floor will be 3 bedrooms so perhaps that is the best location for the intake. Sorry for the novice questions. I have a Zender catalog but I don't fully understand how a system gets installed.

Thanks.

Jamie Hall

Basically, what you want to do is extract air from the house and use the heat in that air to warm fresh air being drawn in to replace it. Zender suggests extracting the air from moist locations, such as bathrooms, but it doesn't have to be so.

So -- what you need is ductwork from your intake to your heat exchanger, then ductwork from there to your heating system return (if forced air) or where you want to discharge it. You also need ductwork from where you want to draw the air to be exhausted to the heat exchanger, and from there to where it gets discharged outside.

Within those limitations, your ductwork can go pretty much where you want it to go. It must be big enough for the air flow, of course, and it must be well sealed.

As to location. The exhaust should be as far as possible from the intake, and the intake, in turn, should be as far as possible from any possible sources of air pollution -- which might be a barbecue grill, a driveway, the street, the vent outlet from a boiler... and, obviously, well above any snow level.

I would add that I have had very very poor results with the sort of heat exchanger which recovers latent heat (humidity) as well as sensible heat, and I can't recommend using those, despite their efficiency being considerably higher.

BillW

Jamie covered about everything, all I would add is to insulate your ductwork, and place the discharges high on the wall to avoid blowing cold air on anyone on really cold days. ER/HRV's are only about 80% efficient.

Zman

If you happen to have a forced air system, it is easiest to tie the house side connections into the duct work as it easier to distribute and raise air temp if needed.

jb9

Thanks for the responses so far. I am planning on using a ductless mini-split to heat the 1st floor and my hope is the 2nd floor as well. I won't have any duct work in the 1st floor ceiling but I will be able to have some ducts in the basement if necessary. How does one deploy an HRV in a house when ductless mini-splits are being used? I am also considering one of the ducted mini cassette units that I could centrally locate (attic) and branch to the 3 bedrooms. I'm not sure if one of those units could work with an HRV. The basement sounds like the best place for one of these units with some ducting to the 1st floor. Not ideal for airflow to the bedrooms but noise is an issue I have heard to be careful about.

Hope that helps give folks a sense. I will probably put some Passive Returns up to increase air flow.

Jamie Hall

The ductwork for the exchangers doesn't have to tie into any other ductwork. See my previous comment for thoughts on where it needs to go.

jb9

Thanks Jamie. I will re-read what you wrote and maybe post a picture of my model with some possible airflow strategies. Thanks for sharing your knowledge.