[Bldg-sim] EPAct 179D Envelope Credit

Patrick J. O'Leary, Jr. poleary1969 at gmail.com
Sat Dec 1 17:07:18 PST 2012

1.  i would recommend obtaining 90.1-2001 and 2004 as the requirements 
of 2001 and the methodologies of 2004 differ from 2010.
2.  don't forget 179d requirements over-ride requirements of 90.1.
3.  do you have the 179d energy simulation guide?  this one is free from 
the nrel website. 40467.pdf is the name of it.
4.  the irs bulletins on the revisions for partially qualifying have 
changed over the years.  most recently (02/12) with an option to use two 
different percentage sets if the building is not fully qualifying until 
12/31/2013.  i.e. 10% building, 15% hvac/swh, 25% lighting OR 10% 
building, 20% hvac/swh, 20% lighting.  the old 16-2/3% for each 
discipline expired at the end of 2008.
5.  and if you're looking at partially qualifying don't forget a 
partially qualifying is each discipline by itself so you can't have a 
partially qualifying hvac/lighting only or hvac/arch.  it would be one 
simulation partially hvac, another partially bldg, or lighting.  and in 
the case of lighting you can use the interim lighting rules which 
doesn't require simulation.
6. can't help you with the use of phase change materials.
7.  the simulations start the same between leed and epact but a) you'll 
see more savings with epact, b) the baseline requirements are different 
(see the 179d simulation guide), and MOST importantly the 179d 
certification is a certification of what is installed on the project.  
i.e. who is field verifying what is there?  you are.  and you're 
certifying this to the irs.  this can make a large difference as far as 
hvac due to your having field measure fan flow, motor volts, and motor 
amps used.  as these should be less than nameplate data you'll see more 
energy savings.  yes, i realize some of the language in 179d reads 
equipment "that will be installed" but if you're using only catalog data 
(which can differ from nameplate) due to trying to certify before the 
building is constructed you won't see as much 179d savings.  don't 
forget you're also certifying building envelope installation and field 
measured lighting levels (there are lighting contractors that can 
provide this) per the 179d requirements.
8.  the 179d savings are an energy cost savings basis.  you have to 
break out the percent cost of energy used by each discipline from the 
total cost of the building based on the percentage energy used by each 
discipline.  see page 9 of the 40467.pdf from nrel.

9.  remember you're only comparing energy for building envelope, 
hvac/swh, and lighting.  as misc/other energies are energy neutral they 
don't impact your savings directly (unlike in leed).
10.  solar pv savings do not apply to 179d, and neither does external 
lighting (it's all internal lighting).  we could have a lot higher 
savings where i'm at if we could include external lighting due to 
stringent site lighting reductions trying to keep our skies dark and 
federally funded telescopes having great views.  solar thermal (swh) 
does apply.


On 12/1/12 2:44 PM, CleanTech Analytics wrote:
> Dear List-
> I am researching the EPAct §179D Energy Efficient Commercial Buildings 
> Tax Deduction, specifically the segment for $.60 per square foot 
> building floor area for building envelopes that contribute to %50 
> better than ASHRAE 2001.   The main question I am attempting to figure 
> out is if Phase Change Materials could be used in conjunction with 
> ASHRAE 90.1 2007 or 2010 prescriptive insulation and fenestration 
> requirements (or better) to achieve the tax credit. The projects that 
> this would apply to are currently going for LEED but may not be going 
> for EPAct.  I am trying to figure out how the envelope contribution to 
> the %50 better than ASHRAE 2001 requirement is segmented to understand 
> if these projects could be applicable for the credit due to the 
> advanced Phase Change Material envelopes.
> I understand that the procedure to follow is ASHRAE 90.1 2004, and the 
> baseline to be 50% above is ASHRAE 90.1 2001.
>   *  Question 1: Is the calculation for %50 reduction similar to the
>     LEED % of cost approach or if it is a % of energy basis?
> The part I do not know is the multipliers to segment the envelope only 
> portion and associated modeling procedures.  If this is based on 
> minimum R values and maximum U values than our product would not 
> contribute to the %50, while if it is based on %50 energy reduction 
> from the baseline envelope energy use than phase change materials 
> could contribute to the credit and receive the $.60 per square foot 
> building area.
>   * Question 2:  How is the envelope segmented from the HVAC and
>     lighting systems when applying for envelope only EPAct?
> I have a budget to buy any required literature, but do not want to 
> misuse funds by buying unnecessary publications.
>   * Question 3: Should I get ASHRAE 90.1 2001 and ASHRAE 90.1 2004, or
>     can I find this info in the ASHRAE 2010 version I already own?
>   * Question 4: Is there any other reference materials that are
>     advised (free or purchased) to better understand EPAct rules and
>     requirements?
> Thank you in advance to anyone who shares their insights..
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