[Bldg-sim] fossil hybrid or electric
Morgan Heater
morgan at ecotope.com
Thu Aug 30 10:47:01 PDT 2012
Thanks for all the discussion. I think a literal interpretation of the
code would actually define the baseline as PTAC with a hot water boiler
for heating. The ASHRAE interpretation actually appears to be a
misinterpretation to me, but as the "misinterpretation" makes more sense
than the code, I'm going to go with it. It is a little quirky, as the 80%
electric vrs 20% gas seems pretty arbitrary. Can we use this on non-res
projects too?
The ventilation scheme described by Mr. Riemer doesn't meet the IBC,
you're not allowed to use a corridor as a duct. Dwelling unit or guest
room doors are supposed to be weather-stripped and make-up air is supposed
to come from the exterior through trickle vents or some other sort of
make-up opening. This doesn't mean that many buildings aren't built that
way of course.
Morgan Heater, P.E.
BEMP, LEED AP
morgan at ecotope.com
206-322-3753 ext 209
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Riemer
Sent: Wednesday, August 29, 2012 2:29 PM
To: 'Bishop, Bill'; Robby Oylear; Rosenberg, Michael I
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric
In the ASHRAE interpretation that Mr. Rosenberg highlighted, the
interesting thing that is missing is ventilation and exhaust. What if the
questioner had said 'exhaust fans in the guestroom toilets, no ventilation
at the PTAC, transferring air under the hallway door, outside air in
rooftop unit determined based on needed guestroom toilet make up'? Would
that have made it a "hybrid"?
I suspect the design did that and thus heated outside air at the rooftop
with natural gas. And the interpretation let the project use the entirely
electrically heated baseline with a good portion of electric resistance
heating. While USBGC/GBCI anticipated that (#2 in their list) and said
"hybrid".
It is increasingly tougher problem to avoid crediting fuel switching. We
will all just keep doing the best we can.
Paul Riemer, PE, LEED AP BD+C
DUNHAM
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Wednesday, August 29, 2012 3:39 PM
To: Robby Oylear; Rosenberg, Michael I
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric
Well that 90.1 Interpretation makes everything clear as mud. There is no
formal definition for "hybrid" system in the Standard, and it is only
explained in the User's manual. A "predominantly" electric-heated system
with some fossil fuel is still a hybrid. Otherwise, what is a hybrid
system?
<mailto:wbishop at pathfinder-ea.com> Senior Energy Engineer 28Jun2012
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Robby Oylear
Sent: Wednesday, August 29, 2012 3:57 PM
To: Rosenberg, Michael I
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric
Interesting. That is obviously the more logical approach, however we now
have two conflicting interpretations. The 90.1 interpretation is more
recent than the LEED CIR. I'm not sure how one would go about challenging
an existing CIR to get it corrected. Does anyone have any experience with
this?
Also, the interpretation does not shed any light on a fossil fuel
preheat/DOAS system serving an electric heating system. I would assume
that this system would still be classified as Fossil/Electric hybhrid and
thus compare to a fossil fuel baseline.
-Robby
On Wed, Aug 29, 2012 at 12:33 PM, Rosenberg, Michael I
<michael.rosenberg at pnnl.gov> wrote:
The interpretation issued by the ASHRAE Standard 90.1 Committee agrees
with Maria.
http://www.ashrae.org/File%20Library/docLib/StdsInterpretations/IC-90-1-20
07-11.pdf
__________________________
Michael Rosenberg, CEM, LEED AP
Senior Research Scientist
ENERGY & ENVIRONMENT DIRECTORATE
Pacific Northwest National Laboratory
2032 Todd Street
Eugene, OR 97405
(541) 844-1960 <tel:%28541%29%20844-1960>
michael.rosenberg at pnnl.gov <mailto:michael.rosenberg at pnl.gov>
www.pnnl.gov <http://www.pnl.gov/>
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Robby Oylear
Sent: Wednesday, August 29, 2012 12:30 PM
To: maria.karpman at karpmanconsulting.net; Vinay Devanathan
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric
Maria,
I'd have to disagree with you. No where in G3.1.1 exception (a) does it
say that you can ignore non-predominant conditions. In fact, if you read
the CIR I quoted it very clearly states an example where 90% of the
building is electric heat and the other 10% is gas-heat (less than 20,000
SF) and the baseline model is determined to be Fossil/Electric Hybrid.
You may be thinking of the footnote to Table G3.1.1A which states "Where
attributes make a building eligible for more than one baseline system
type, use the predominant condition to determine the system type for the
entire building." However, the CIR is counter to this, and since Table
G3.1.1A includes a category for Fossil/Electric Hybrid, your building
would only fall into one category.
Vinany - the CIR addresses that exact scenario and states that gas
furnace-fired DOAS puts you into the Fossil/Electric Hybrid category and
your baseline would be System 1 PTAC with HW.
-Robby
On Wed, Aug 29, 2012 at 12:13 PM, Vinay Devanathan
<vinay.devanathan at gmail.com> wrote:
What would be the case for a project with residences using Heat Pumps for
conditioning and a gas furnace-fired DOAS for ventilation to residences
and common spaces?
Vinay
On Wed, Aug 29, 2012 at 3:09 PM, Maria Karpman
<maria.karpman at karpmanconsulting.net> wrote:
I think that in Morgan's case using PTHP baseline is also justified. From
what I understand, the project is a residential buildings with
electrically heated living units and gas-heated common spaces. Applying
G3.1.1 to the project, predominant conditions are residential with
electricity as heat source; non-predominant conditions are non-residential
with fossil fuel heat. Based on G3.1.1 exception (a), non-predominant
conditions accounting for less than 20,000 SF may be ignored when
selecting the baseline system from Table G3.1.1A, thus the baseline for
the project is PTHP. If residential units were served by WSHP, then
predominant conditions would be residential with Fossil/Electric Hybrid
heating source, and the baseline system would by PTAC.
Maria
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Robby Oylear
Sent: Wednesday, August 29, 2012 11:14 AM
To: Morgan Heater
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] fossil hybrid or electric
Morgan,
I agree with Bill. I find this LEED CIR (see below) to be helpful in
determining how fossil/electric hybrid systems should be handled. Your
scenario sounds similar to item 5 under the examples of systems that would
be modeled with fossil fuel heating.
LEED Interpretations
11/1/2011 ID#10132
. MPR/Prerequisite/Credit: EAp2: Minimum Energy Performance
. Primary Rating System: Core & Shell v2.0
Email
Ruling
Clarification is requested regarding when a building heat source in Table
G3.1.1A should be identified as "Fossil/Electric Hybrid" versus
"Electric".
The ASHRAE 90.1-2007 User's Manual states that a fossil/electric hybrid
source "refers to a system with any combination of fossil and electric
heat, and the baseline system for this is a fossil fuel system".
Therefore, the heating source for the proposed building would be
considered "Fossil Fuel" or "Fossil/Electric Hybrid" if the building uses
any fossil fuel source for space heating (including backup heating or
preheating), and the baseline building heat source would be fossil fuel.
Exception: ASHRAE 90.1 Section G3.1.1 Exception (a) stipulates additional
system type(s) for non-predominant conditions (i.e.
residential/non-residential or heating source) if those conditions apply
to more than 20,000 square feet of conditioned floor area.
EXAMPLES OF BASELINE HEATING SOURCE DETERMINATION:
The Baseline heat source from Table G3.1.1A for the following Proposed
Case system types would be fossil fuel since the proposed system design
includes a combination of fossil and electric heat:
1. Variable air volume system with gas furnace preheat and electric reheat
2. Packaged terminal heat pumps with outside air tempered by fossil fuel
furnace
3. Water source heat pumps with fossil fuel boiler
4. Ground source heat pumps with backup fossil fuel boiler
5. 90,000 square feet is conditioned by a variable air volume system with
electric reheat, and 10,000 square feet is conditioned with fossil fuel
furnaces
The following buildings would be modeled with an additional system type
with a different Baseline heating source in accordance with Section G3.1.1
Exception (a):
1. 90,000 square feet is conditioned by a variable air volume system with
electric reheat, and 20,000 square feet is conditioned with Packaged DX
systems with fossil fuel furnaces. In this case, the 90,000 square feet of
area would be modeled with an electric heat source in the Baseline Case
(System Type #6 - Packaged VAV with Electric PFP Boxes), and the 20,000
square feet of area would be modeled with a fossil fuel heat source in the
Baseline Case (System Type #3 - Packaged Single Zone AC with fossil fuel
furnace).
2. 50,000 square feet is conditioned by water source heat pumps with a
fossil fuel boiler, and 25,000 square feet is conditioned by electric heat
pumps. In this case, the 50,000 square feet of area would be modeled with
a fossil fuel heat source in the Baseline Case (System Type #5 - Packaged
VAV with hot water reheat), and the 25,000 square feet of area would be
modeled with an electric heat source in the Baseline Case (System Type #4
- Packaged Single Zone Heat Pump).
Applicable Internationally.
Formal Inquiry
Table G3.1.1A lists two possible categories for the building heating
source:
(1) Fossil fuel, fossil/electric hybrid, & purchased heat;
(2) Electric and other.
In cases where the proposed building design includes both a natural gas
heating source and an electric heating source, when should the heat source
in Table G3.1.1A be identified as "Fossil/Electric Hybrid" versus
"Electric"?
Robby Oylear, PE, LEED AP
Mechanical Engineer
Senior Energy Analyst
D 206-788-4571
<http://www.rushingco.com/> www.rushingco.com
On Tue, Aug 28, 2012 at 5:41 PM, Bishop, Bill <bbishop at pathfinder-ea.com>
wrote:
Morgan,
My vote is for PTAC with hot-water boiler.
Regards,
Bill
<mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com> From:
bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Morgan Heater
<mailto:wbishop at pathfinder-ea.com>
Sent: Tuesday, August 28, 2012 8:12 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] fossil hybrid or electric
<mailto:wbishop at pathfinder-ea.com>
Hi <mailto:wbishop at pathfinder-ea.com> - I've got an appendix G baseline
system question. Here's the scenario, let me know what you think.
<mailto:wbishop at pathfinder-ea.com>
Proposed Building: <mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com>
1. <mailto:wbishop at pathfinder-ea.com> Multi-family residential,
amenity/common space < 20,000 square feet
2. <mailto:wbishop at pathfinder-ea.com> Electric baseboard heat in
the units
3. <mailto:wbishop at pathfinder-ea.com> Condensing gas furnaces in
the corridors and back of house spaces
4. <mailto:wbishop at pathfinder-ea.com> VRF in amenity common spaces
<mailto:wbishop at pathfinder-ea.com>
My understanding is that because my <mailto:wbishop at pathfinder-ea.com>
non-predominant condition (common/amenity space) is less than 20,000
square feet, I use a single system for the whole baseline building
(G3.1.1a). I've got a mix of gas and electric heat in the baseline
building, does this mean that my base system is PTAC with a hot water
boiler?
<mailto:wbishop at pathfinder-ea.com>
Thanks! <mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com>
Morgan Heater, P.E. <mailto:wbishop at pathfinder-ea.com>
BEMP, LEED AP <mailto:wbishop at pathfinder-ea.com>
morgan at ecotope.com <mailto:wbishop at pathfinder-ea.com>
206-322-3753 ext 209 <mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com>
<mailto:wbishop at pathfinder-ea.com>
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