Efficiency of ERV Units when Calculating Peak Load

I personally wouldn't advocate for adjusting load calculations for errors in ongoing O&M since we already have so many other factors typically included into the design to begin with... which contribute to oversizing. Hard to get our engineering brains to stop doing that, but really cricitical on a passive house project. Is this multifamily residential? What are they using for the load calc program? WUFI Passive or something else? Is this ERV serving the whole building? 

90.1-16 requires energy recover systems (prescriptive) to perform at an enthalpy recover ratio of at least 50% (change in the enthalpy of outdoor air divided by the difference between the outdoor air and entering exhaust air enthalpy, expressed as a %, calculated using units of Btu/lb-dry air). So I would assume that as an absolute worst case scenerio. Double check that airflows are balanced and that you all are thinking / looking / talking about / entering is in terms of total energy / enthalpy and not just sensible energy?

From Columbia's MEP Services Director:
"See attached and link below from the Heating & Ventilating Institute (HVI) for information on ERV & HRV efficiencies and effectiveness.  This is an independent testing agency and I have no reason to believe that they would manipulate values.  The attached sheet defines the values that are contained in the tables/ spreadsheets that they provide.  These are utilized for modeling purposes.  The data is current as of June 24, 2022.  They also offer the option of downloading detailed energy ratings in an excel spreadsheet, which I expect could be uploaded into an energy evaluation software program (eQuest, etc.). https://www.hvi.org/hvi-certified-products-directory/section-iii-hrv-erv-directory-listing/            Also, some information from ASHRAE for a project in Roxbury with HRVs that has been functioning for about 10 years:  https://www.hpbmagazine.org/roxbury-e-townhomes-boston/     Unfortunately, the energy monitoring link doesn’t exist anymore, but I would expect that resident satisfaction is still high.  My assumption is that the efficiency of the HRVs would have been modeled per manufacturers information and the building energy performance is better than was predicted by calculation. "

I'm checking to verify if this info is relevent for Large Commercial also. He may have missed that part of the question...

"Large commercial would be rated by AHRI.  This is the main page for commercial ERVs:  https://www.ahridirectory.org/NewSearch?programId=39&searchTypeId=3                        Similar interface to the HVI website but you need to enter the manufacturer."

I second Sarah’s last statement about balancing the airflows. The effectiveness of energy recovery can be derated significantly if the exhaust/relief airflow is significantly lower than the outside/intake airflow. Historically the reason for this difference in airflows has been due to building pressurization. As buildings become tighter, engineers likely need to reduce the assumptions for airflow leaving the building through cracks in the envelope, which should help these numbers. Patrick Murphy, PE, LEED AP BD+C, CPHC Associate Principal | Director of Sustainable Design R.G. Vanderweil Engineers, LLP T 617.956.4804 | C 607.621.8047 www.vanderweil.com [cid:image001.gif@01D895FB.CBD78A20] [cid:image002.gif@01D895FB.CBD78A20] [cid:image003.gif@01D895FB.CBD78A20] [cid:image004.jpg@01D895FB.CBD78A20] F