[Bldg-sim] fossil hybrid or electric

Rosenberg, Michael I michael.rosenberg at pnnl.gov
Wed Aug 29 12:33:39 PDT 2012


The interpretation issued by the ASHRAE Standard 90.1 Committee agrees with Maria.

http://www.ashrae.org/File%20Library/docLib/StdsInterpretations/IC-90-1-2007-11.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
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<mailto: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<mailto: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> [mailto:bldg-sim-bounces at lists.onebuilding.org]<mailto:[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<mailto: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<https://www.usgbc.org/leedinterpretations/LIDetails.aspx?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>
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<tel:206-788-4571>
www.rushingco.com<http://www.rushingco.com/>

On Tue, Aug 28, 2012 at 5:41 PM, Bishop, Bill <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>> wrote:
Morgan,

My vote is for PTAC with hot-water boiler.

Regards,
Bill

 <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>
 <mailto:wbishop at pathfinder-ea.com>
Hi - 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>
 <mailto:wbishop at pathfinder-ea.com>
Proposed Building:<mailto:wbishop at pathfinder-ea.com>
 <mailto:wbishop at pathfinder-ea.com>

1.       Multi-family residential, amenity/common space < 20,000 square feet<mailto:wbishop at pathfinder-ea.com>

2.       Electric baseboard heat in the units<mailto:wbishop at pathfinder-ea.com>

3.       Condensing gas furnaces in the corridors and back of house spaces<mailto:wbishop at pathfinder-ea.com>

4.       VRF in amenity common spaces<mailto:wbishop at pathfinder-ea.com>
 <mailto:wbishop at pathfinder-ea.com>
My understanding is that because my 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>
 <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>

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--
Vinay Dev


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