We are following the option 2 ASHRAE AEDG presciptive path for a project. One of the AEDG requirements for HVAC is for a heat pump >135 kBtuh to be at minimum 10.1 EER or above. We have specified a 20 ton unit at 9.7 EER which does not meet the requirement.
However, we believe that the requirements are inconsistent with ASHRAE 90.1-2007, which the AEDG is supposedly based on. ASHRAE 90.1-2007 has their requirement for a heat pump >=240 kBtuh at 9.5 EER. This size category doesn't appear in the LEED requirements. Could we use the IEER rating instead because of this discrepancy? The IEER rating for our unit is 11.5 IEER. Please advise.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5924 thumbs up
March 7, 2013 - 12:25 pm
You must meet each of the prescriptive requirements of the AEDG in order to be eligible to use it. The idea behind the AEDG is to exceed the 90.1 minimums and the two are not always going to be compatible. So a discrepancy between the two is not a reason to not meet the AEDG requirements (sorry for the double negative).
Heather Holdridge
Sustainability DirectorLake|Flato Architects
111 thumbs up
March 7, 2013 - 12:41 pm
Thanks for the prompt response. I'm also realizing that we are running into issues because option 2 specifies office occupancy and we are technically public assembly (with some office occupancy).
Scott Bowman
LEED FellowIntegrated Design + Energy Advisors, LLC
LEEDuser Expert
520 thumbs up
March 7, 2013 - 12:45 pm
We have tried using the AEDG a couple of times, and have one project that was certified using it. However, our experience has been that showing compliance can be as or more difficult than doing the energy modeling, and no longer recommend our clients proceed this way. That is our experience, and we have normally been able to gain more points through the modeling than the AEDG.
Now, that being said, we like the AEDG’s, especially the newer 50% versions, as great starting points in system selection and guidance. They provide great starting points.