EPACT Simulations Questions

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Building simulations for EPACT credits require that the building energy
and power costs be reduced by 50%. The tax credit has been extended to

The energy and power cost savings must come from a 16-2/3% reduction in
three categories: Building envelope, HVAC and SHW, and Lighting. There
is a guideline called "Energy Savings Modeling and Inspection
Guidelines for Commercial Building Federal Tax Deductions" Second
Edition, which is Technical Report NREL/TP-550-40467, May 2007.

In this guideline, they describe the technique on pages 3 and 4 to
calculate the costs and % cost reductions due to the Lighting, and
HVAC/DHW electricity use. Nowhere does it describe how they want you to
calculate the cost and cost reductions due to the building envelope,
despite the fact that 16-2/3% of the energy savings are required to come
from this category.

Does anybody know what to do for the building envelope and the EPACT

Has anyone seen a spreadsheet available already created to do the cost
allocations based on the outputs from a simulation program (in my case
Trane Trace 700)? There are quite a few available for the simple
"Interim Lighting Rule" but none that I have found for the full model.

Also, in April 2008, an IRS Notice 2008-40 called "Amplification of
Notice 2006-52" describes being allowed to change the portion of the
savings for the building envelope to 10% if the Lighting and HVAC/DHW
savings are increased to 20% each (for a total remaining at 50% energy
and power cost reduction).

Has anybody seen this used? I have searched around for examples of
EPACT and all places still reference the 16-2/3% thresholds.

Nick Anderson

Nick Anderson's picture
Joined: 2011-10-02
Reputation: 0

When making a partial qualifier analysis, the other aspects of the proposed building are relaxed to match the baseline building.

If you are attempting an HVAC partial qualifier for instance, the proposed and baseline building would be identical for lighting design and envelope design, and you'd have to achieve 20% under the newer rules. (16-2/3% for a building partially qualifying under the old rules.)

The 20% (16-2/3%) will then be wholly attributable to the HVAC systems. To partially qualify for envelope, you'd repeat this process in a second set of simulations with the proposed envelope, but baseline lighting and HVAC while claiming 10% savings (16-2/3%). Etc.

If your client had a whole-building qualifier, then you would have all different aspects of your proposed design incorporated, but have to achieve 50% savings. The savings do not have to be allocated to each partial area in this case.

It won't be too hard to make a spreadsheet to show the savings. Similar to what you might have done for any other ECB or Appendix G analysis.

David Eldridge, PE, LEED(r) AP

David S Eldridge's picture
Joined: 2011-09-30
Reputation: 2000

Hey Nick:

The baseline for building envelope is 90.1-2001. Construct your building as
built to that standard and calculate usage. Your 50% (or whatever
percentage) savings is calculated based upon energy usage reduction
generated beyond that baseline not your actual building.


Andy Hoover

Andy hoover's picture
Joined: 2011-10-02
Reputation: 0

How do you rectify the unmet load hours for a two pipe system? Such
that there will certain periods of the year where the heating only is on
but cooling is required due to internal and skin loads, hence the unmet
load hours.

Timothy Howe, MS, LEED(r) AP

Howe, Timothy's picture
Joined: 2011-09-30
Reputation: 0

Anyone have experience with Indirect Evaporative Cooling (i.e.
Coolerado) in EnergyPro or eQuest?

We have a an office retrofit and are trying to model and quantify the
benefits of this system in the mild San Diego climate.
Any help is appreciated, thanks.

Douglas Kot, AIA, AICP

Kot, Douglas's picture
Joined: 2011-09-30
Reputation: 0

Dear Doug,


I'm not familiar with EnergyPro or EQuest. (EnergyPlus is my
analysis tool.)

I AM familiar with Coolerado.

The key to a reasonable model, in my opinion, is to get the cooling
performance suitably high (much better than typical indirect evap) and also
the fan HP correct, which tends to be higher than an indirect evap.

The Coolerado folk have tested the heck out of their HMX and have
very good equations for it's performance. You might be able to curve-fit
within your software....

Finally, Coolerado is normally a blow-through application and thus
treats fan heat differently than indirect evap.

Good luck!

James V. Dirkes II, P.E., LEED AP

James V. Dirkes II  P.E.'s picture
Joined: 2011-10-02
Reputation: 0