I’m failing IECC 2012 with the HRVs we’ve been using – Honeywell .  (See specs below that I entered into REM for another rating.)  I’m getting error/fail messages that the fan efficacy isn’t what’s required.

(My REM inputs:  sensible recovery efficiency 61%, 100 CFM, 24 hours/day, 106 fan watts).

I’ve been researching some HRVs that might, just might pass like the Zehnder 350.  So I tried modeling THAT in this house.  No go.  I even tried modeling like a PERFECT HRV – 100% sensible recovery efficiency.  STILL no go.


HELP!  I’ve got projects that are snagged at permitting b/c of this.  There is one thing I wonder about – these houses are BIG (5,000 s.f. or so), and my HVAC contractor says he has to use the Honeywell models to push enough air.  Hmm …   


Anyway, ‘really need some guidance here as soon as you can render it..  Thanks!

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commercial is 67% efficiency & 2.8 cfm per watt for residential as I recall on 2015 which looking at your numbers you are toast on both - with that are you sure about that wattage? Is this integrated into the HVAC, if so there is an exemption for that

"they are exempt from the efficacy requirement as long as they are equipped with an electronically commutated motor (ECM)"

I'm not sure if this will make a difference in your inputs but I found the above quote from IECC. Thought it might change how you are inputting your ERV numbers.

UltimateAir Inc has been using EC/DC motors for 20 years. I believe Venmar & RenewAire both have at least 1 model providing these now. The Zehnder unit you modeled should have had ECM motors as well.

It sounds like your (100cfm) may be too low for a 5000sf house. Are you following 62.2? Also, Zehnder wattage should be around 24W from my knowledge. These units have been installed in Passive Houses. The sensible recovery seem low as well.

I would recheck the spec's on your equipment.

Thanks, guys.   This is all really helpful.


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