LEED review comments for System 5 heating source

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Lan,
I have always taken G.3.1.3.2 to mean the same FOSSIL fuel as the proposed design to prevent switching between natural gas, fuel oil, coal, and propane. Reading electric might feel okay until you get to the natural draft clause.

Assuming your Proposed electric heating consumption includes both your misc. heaters and VFR compressors operating in heating mode, I suggest your system is Fossil/Electric Hybrid heat and that you should model system 5 with natural gas boiler(s) and check the 'other' box noting hybrid heat. If you want to be compared against electric heated (system 6 with fan powered boxes & electric resistance), you need to get the gas in your OA unit set aside like an old CIR did for gas preheat.

The beta LEED interpretations database has elevated some CIRs to be precedent setting for LEED 2009+, maybe that gas preheat one made the list. Their website has been a bit skittish for me lately, so I suggest you to go USGBC.org, use the sign in link and then go to LEED - Certification Tools - LEED Interpretations. I say skittish because I get an error if I try navigate to the interpretations page and then log in.

Paul Riemer, PE, LEED AP

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Paul, Paul and Carol,

This sentence just jumps into my eyes. It is on ASHREA 90.1-2007 User's
manual page G-22.

Here is the interception.

The performance rating rules for the baseline building HVAC system are
shown in Table G-A. This table shows the baseline building system types,
based on building type (nonresidential or

residential), the number of floors, the floor area and the heating
source (electric or other). Note that a hybrid system refers to a system
with any combination of fossil and electric heat, and the baseline
system for this is a fossil fuel system.

I think I will stick with my gun and go for it. I will keep all of you
posted for the outcome of my review. Hopefully everyone will be clear on
this matter then.

Thanks!

Lan

Lan Li, PE, LEED AP BD+C

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Lan:

In the Advanced Energy Modeling for LEED Technical Manual v.1 page 28 under
ASHRAE 90.1-2004 common errors for HVAC System, primary system type, the second
error is 'Baseline HVAC systems use both fossil fuel and electricity'.

I assume this is why your reviewer requested that the baseline be changed to the
predominate heating energy source that was used in the proposed model.

Paul Diglio

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Paul - thanks for raising that.
Lan- If your ?misc. elec. heaters? are in zones that are also served by your VRF system, then they are akin to baseboards and should not be modeled in your Baseline. If they are in zones separate from your VRF, then you might have to revisit G3.1.1 and the exceptions to see if those zones qualify for separate system(s). If they are electric resistance heating in vestibules, restrooms, or stairwells, those cases are fuzzy to me and I need to do more research.

Paul Riemer, PE, LEED AP

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Lan:

No, I could not find a section that mentions the predominate heating source of
the proposed be used as baseline heating source.

The Advanced Energy Modeling manual costs $120.00 and is available only for
download. It is a secure document and cannot be printed as a PDF, it can be
printed to hard-copy.

Based on G3.1.3.2 and the Advance Energy Modeling manual extract below, my
understanding is that the baseline system can only use one source of fuel for
the HVAC systems and the baseline boiler plant for system 5 shall use the same
type of fuel as the proposed. Does ASHRAE consider electricity as a fuel? In
the 90.1-2004 definitions fuel is defined as 'a material that may be used to
produce heat or generate power by combustion'.

Another example of the lack of coordination between LEED and ASHRAE 90.1.

If I understand your design correctly, your DOAS is using a natural gas furnace
and you have a VRV system for the space heating and cooling requirements. So
your actual proposed heating source is electricity with a small secondary
natural gas use to precondition the outside air. Since LEED says you cannot
have two energy sources for the HVAC systems in the baseline, your reviewer is
requesting that you use the proposed predominate source for the baseline.

Would it not increase your energy savings to do as the reviewer requests?

Paul Diglio

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Yes, for sure it would give me more points as I tried on other projects
before. We are buying the book right now.

Thanks!

Lan

Lan Li, PE, LEED AP BD+C

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I have always interpreted it that when I have a major gas use, and heating
outside air is what I'd call major, in a building that otherwise uses heat
pumps, that my baseline will be a hybrid system. I think we've been through
this discussion on this website before, too.

It does not "feel" right to me to call the baseline version of a proposed
building that has heat pumps and a gas furnace an electric baseline. I is
too much like getting credit for a fuel switch, and yes from "electric" fuel
to a "fossil" fuel, and where I come from that's a no no of the first order.

I think ultimately you must use your best judgement, do what feels right to
you and defend it.

Carol

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The reference to the predominant condition is the third footnote under Table G3.1.1A.

Cam S. Fitzgerald, PE, LEED AP

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Which is really confusing isn't it, since they specifically list a
Fossil/Electic hybrid as a header on that table. Argh!

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Paul (and maybe others):
I feel like you might be asserting either ?just do whatever the reviewer tells you? and/or ?When the Proposed heating is a hybrid of fossil fuel and electric hybrid, the Baseline heating source shall be determined by whichever consumption is larger in the Proposed model.? And I just can?t get on board with either of those statements.

To the electric boiler suggestion, the whole right column addresses electrically heated baselines and each row results in either heat pump or electric resistance. I could infer scenarios where Lan could get all or parts of his baseline building to the ?electric and other? column but I cannot see any scenario that ends up with an electric boiler in the baseline of Appendix G model. I do recoil a bit that Appendix G always compares hybrid systems to a fossil fuel baseline but I do think 1) that is its intent and 2) to write that table another way seems like an rather daunting challenge.

Paul Riemer, PE, LEED AP

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I am with Carol on this one. I think my case is quite clear on Table
G3.1.1.A. Thanks!

Lan

Lan Li, PE, LEED AP BD+C

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To all,

We have gotten response from USGBC review team. We are correct to use gas as heating source for the base design. Thanks for all your inputs.

Have a nice weekend!

Lan

Lan Li, PE, LEED AP BD+C

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