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!

Views: 188

Reply to This

Replies to This Discussion

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.



  • Add Videos
  • View All

Latest Activity

Profile IconDamon Morales, Thermodyne Boilers, Michael Woodham and 1 more joined Home Energy Pros
3 hours ago
marius gherman posted a video

Winter conditions, perfect operation - ROTEX / DAIKIN heat pump

FIAMMA company, ROTEX partner in Romania, offering turnkey packages to improve energy efficiency, from supply to installation. With an experience of over 25 ...
3 hours ago
Profile IconJeffery Liang and Ellen Phillips Soroka joined Home Energy Pros
Charles Cormany added a discussion to the group Job Board

Energy Efficiency Incentive Program Manager - Efficiency First California (Berkeley)

Position Title: Program Manager Terms: Full time, available immediatelyAbout Efficiency First…See More
Charles Cormany joined Diane Chojnowski's group

Job Board

This group is for posting jobs related to all aspects of the home performance industry including…See More
Linda Wigington liked Home Energy Magazine's blog post Art Rosenfeld's Legacy
terry nordbye added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase

Combustion anaylizer Testo 310

This little beauty only has a few hours on it. Almost brand new in box.Sell: $350.Terry 415 669…See More
Barbara Smith's video was featured

Indiana HCA...On Location - Celebrating 40 Years of the Weatherization Assistance Program (WAP)

The Indiana Housing and Community Development Authority (IHCDA) interviewed two clients of Weatherization Assistance Program (WAP). Both homes were weatheriz...

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported by the U.S. Department of Energy) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service