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Air Sealing HRV

calum_wilde | Posted in Mechanicals on

First off, a little about my situation. I live in Nova Scotia, in an 11 year old split entry, ~1200 sqft per floor with a fully ducted HRV. I had an energy assessment completed a couple of days ago. The results of the blower door test were good, 1.91 ACH and Equivalent Leakage Area 335 cm2. I’ve started sealing up some obvious air leaks, but one thing that crossed my mind is that the HRV only runs 20 minutes per hour at minimum speed, and only during the day. Well, when we shower there’s about 40 minutes of full speed, but that’s it. So, then the HRV isn’t running it’s just a great big gaping hole (182 cm2 to be accurate.) in the side of my house, that leads right into each and every room. My HRV, a Fantech SHR1504, doesn’t have any dampers inside to prevent flow when it isn’t running.

So, my question is, should I add dampers to prevent flow when my HRV isn’t running? And if so, how and with which products?

Thanks for any help.

Oh, and before the obvious questions is asked; running the HRV at 20:40 for ~12 hours per day keeps the windows dry and I still have to cook with the lids off the pots to add a little humidity in order to avoid sinus issues.

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Replies

  1. calum_wilde | | #1

    It seems I can't delete a post, and now a feel like a tool. I searched google and my local hardware stores websites but couldn't find anything for an HRV vent hood damper, vent hood damper, ducting damper, etc. etc. I did find a bunch of things about motorized for use when ducting an HRV into a furnace, and I think once or twice I landed on something about back draft preventers, but somehow in my mind I assumed they were for fire regulations. Anyway, I found what I needed when I read a few posts down. If you're reading this, sorry for wasting your time, and this sites bandwidth. I'll go back to lurking now.

  2. Chaubenee | | #2

    Bandwidth crisis is almost as great as the landfill crisis.

  3. charlie_sullivan | | #3

    It's a legitimate question. Backdraft dampers with strong springs introduce resistance to airflow. Backdraft dampers with weak or no springs won't resist wind-induced flow in one direction. Motorized dampers usually power the motor to open, and continue powering the motor, wasting electricity, the whole time it's open.

    The airflow resistance of a strong-spring damper isn't an issue for something like a range hood or a clothes dryer, but for an HRV you want to run long hours, efficiency matters. If you have a good adjustable speed ECM fan, you can reduce its power draw if the ducting has less resistance. And if you don't have that capability, and are instead adjusting average flow by adjusting run time, you will need less run time if you impede the airflow less.

    One answer might be that there's perhaps at least a little heat recovery still going on when you have leakage through the HRV, so you can consider that as a part of your desired HRV ventilation.

  4. calum_wilde | | #4

    @Charile Sullivan

    Thanks, I was thinking about putting motorized dampers on. For the amount my system runs the power draw shouldn't be a concern. I'm going to see if my HRV is capable of powering them and then go from there.

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