ASHRAE 90.1 Window to Wall area definition

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Example 5-Q in the 90.1-2013 User?s Manual still uses both above-grade and below-grade walls as ?exterior walls? for determining gross wall area.

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

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The 'Standard Definitions of Building Geometry for Energy Evaluation'
technical report issued by NREL defines WWR as the ration of Wall
Fenestration Area and the Gross Above-Grade Wall Area.

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David is correct regarding prescriptive compliance with Section 4 in 90.1. However, 2010 Appendix G in table G3.1.5 clearly states that baseline WWR is limited to 40% of ?gross above grade wall area?. This is an important distinction.
__________________________

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Senior Research Scientist
ENERGY & ENVIRONMENT DIRECTORATE

Pacific Northwest National Laboratory
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The 90.1-2007 User?s Manual, example 5-K indicates the same rule.

[cid:image003.png at 01D09C46.E75BA0D0]
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Unconditioned parking garage would not contribute to your WWR. Only
conditioned underground space should be counted.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

ASHRAE interpretation IC 90.1-2004-1 dated June 25, 2005 states that gross wall area is ?the area of the wall measured from the exterior face from the top of the floor to the bottom of the roof?.

It goes on to say that buildings with conditioned below-grade space, the gross wall area includes below-grade space.

Cheryl M. Saldanha, P.E. (CA)
Senior Staff I - Building Technology
SIMPSON GUMPERTZ & HEGER
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Page 213 of 90.1-2010 says ?above-grade?

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Shaun Martin LEED-AP, BEMP

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Expanding on Michael?s and Elizabeth?s comments?
Note that Appendix G. specifically refers to ?above-grade wall area? for determining fenestration percentages (in 2007, 2010 and 2013 versions).
Also note that ?parking garages with natural or mechanical ventilation are not considered enclosed spaces? per 90.1 definition of space. Therefore, any ?walls?, whether above or below-ground, are not part of the building envelope, are therefore not technically walls per 90.1 and wouldn?t be included in WWR calculations.

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

[cid:image001.jpg at 01D1074F.03C72A50] [cid:image009.jpg at 01D1074F.03C72A50]

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T: (585) 698-1956 F: (585) 325-6005

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But to further complicate things, my understanding is that if you have an enclosed-conditioned space within the parking garage (elevator lobby, maintenance room, etc), and walls of that space that border the unconditioned parking garage you WOULD count that as above-grade wall.

The most complicated scenario is a conditioned room tucked along the perimeter of the parking garage. In that case you WOULD COUNT the walls that separate the space from the unconditioned garage as part of the App G WWR calc, but you WOULD NOT COUNT the below grade walls that separate that space from dirt in the App G WWR calcs.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100
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I have NEVER heard of WWR ratio including below grade walls. ?California Title 24 never has.

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From:"Jones, Christopher"
Date:Thu, Oct 15, 2015 at 10:15 AM
Subject:[Bldg-sim] ASHRAE 90.1 Window to Wall area definition

I know this question has been asked before but I could not find a related thread.

?

90.1 states that the WWR is based on the gross wall area and the definition of gross wall area includes below ground walls as well as above ground walls..? Including the below grade walls can make a significant difference in the WWR for typical urban high rise buildings with a number of below grade parking floors.?

?

Can someone confirm that the WWR calculation is based on above grade wall area plus below grade wall area?

?

?

?

Christopher Jones, P.Eng.
Senior Engineer

?

WSP Canada Inc.

2300 Yonge Street, Suite 2300

Toronto, ON M4P 1E4
T +1 416-644-4226

F +1 416-487-9766

C +1 416-697-0056

?

www.wspgroup.com

?

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That is a great point. Appendix G is different from the prescriptive
requirements.

The prescriptive requirements (and thus Energy Cost Budget method) allow
you to count below-grade conditioned walls as per section 5.5.4.5 as part
of your "gross wall area", while Appendix G specifically says above-grade
walls only.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
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You people rock. I got way smarter in 5 minutes of reading your posts than
5 hours of scouring references.

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So up here in Zone 6 and 7 where the first level of parking below grade is often heated enough to make it a conditioned space, one would count those below grade walls in the WWR for the Energy Cost Budget method. That can make a somewhat significant difference in how much glazing the baseline case has in the above grade walls.

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
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It would have to be heated enough to qualify per Table 3.1, which would be
pretty high:

[image: Inline image 1]

And then you would have to insulate it like a conditioned space (rather
than just a semi-heated space). But yes, then you could count it!

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Thanks Elizabeth,
Your reply brings up another question. If the proposed design meets the requirement of Table 3.1 does the baseline automatically follow suit? Or does one have to first construct the baseline case model to determine the self-sized heating capacity to determine if the space is conditioned or semi-heated? It sounds like it would be an iterative process ? first model the space with exterior insulation for a conditioned space then determine the heating capacity. If it shows a semi-heated space, then change the insulation and check again, and so on?

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

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According to my understanding it would be based off the proposed.
Thanks Elizabeth,
Your reply brings up another question. If the proposed design meets the requirement of Table 3.1 does the baseline automatically follow suit? Or does one have to first construct the baseline case model to determine the self-sized heating capacity to determine if the space is conditioned or semi-heated? It sounds like it would be an iterative process ? first model the space with exterior insulation for a conditioned space then determine the heating capacity. If it shows a semi-heated space, then change the insulation and check again, and so on?

[cid:image001.png at 01D10759.6D80DAE0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

www.wspgroup.com

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Whether you choose to build your baseline before/during/after your proposed
case, you will need to very actively reference the proposed/actual design
along the way to determine where the conditioned spaces lie (per the
glossary entries), and from there where the envelope line is drawn
separating the conditioned from the exterior/unconditioned/semi-conditioned
areas.

Insofar as the WWR discussion thread goes, I believe I?m situated in
Nathan?s camp. I simply (?) equate/read ?above-ground? in Appendix G to
mean ?not facing dirt,? regardless of where the grade lies.

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
306 N Ferrel

Olathe, KS 66061

office: 785.410.3317

www.catonenergy.com

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This discussion is very interesting and relates to another question I asked before, and since it didn't get much traction and this one did, please allow me to bring it up again.

For above grade walls that are abutting an existing building (adiabatic), do you include those in the WWR calculation or exclude them?

Thanks,
Julien

Envoy? de mon iPhone

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Another interesting question!

If you look at how ASHRAE 90.1 defines "exterior building envelope", as
being "the elements of a building that separate conditioned space from the
exterior space", then I would say that no, your adiabatic walls do NOT
contribute to your building envelope or your WWR, because they do not abut
exterior space. So you should exclude them from your calc.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

I agree, but can envision a few real-world cases where you might definitely
call the abutting walls part of the conditioned envelope, but would still
fall into the ballpark of ?a grey area:?

? What if the two abutting buildings aren?t sharing a wall, but
rather an enclosed unconditioned void/cavity?

? What if you aren?t comfortable calling it an adiabatic surface
(i.e. the adjacent building is unconditioned/unoccupied)?

I think I?d fall back on a ?gut check? in such instances: If it makes zero
sense to install glazing for any proposed case design, then you should feel
safe consistently excluding those surfaces from the resultant WWR
requirements on the baseline side. Put another way, don?t make the
baseline include windows where it?s completely unreasonable (this also
encompasses my ?facing dirt? litmus test).

I know that isn?t terribly black & white ? I wouldn?t be surprised if some
specific urban energy codes have tread these paths enough to address the
various possibilities for abutting buildings? (?)

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
306 N Ferrel

Olathe, KS 66061

office: 785.410.3317

www.catonenergy.com

*From:* Elizabeth Gillmor [mailto:elizabeth at energetics-eng.com]
*Sent:* Friday, October 16, 2015 3:32 PM
*To:* Julien Marrec
*Cc:* Nicholas Caton; Jones, Christopher; bldg-sim at lists.onebuilding.org
*Subject:* Re: [Bldg-sim] ASHRAE 90.1 Window to Wall area definition

Another interesting question!

If you look at how ASHRAE 90.1 defines "exterior building envelope", as
being "the elements of a building that separate conditioned space from the
exterior space", then I would say that no, your adiabatic walls do NOT
contribute to your building envelope or your WWR, because they do not abut
exterior space. So you should exclude them from your calc.

*Elizabeth Gillmor **PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*

energetics-eng.com

c 303.619.0091

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Julien,

Wouldn?t a wall abutting to another wall that is conditioned on the other side make it an interior wall instead of an exterior wall? It?s effectively an addition to the other building.

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

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Keith,

It's an interesting point of view.

Different owners most of the time in my experience (happens all the time in NYC), the adjacent building is a black box in my opinion. Might or might not be occupied or conditioned to the same level now or 5 years from now, and you are likely to just be speculating about what's going on inside.

To some extend I might even be advocating to insulate these walls (though I'm guessing I'll have a hard time selling this to a developer)... I've seen enough existing buildings running into (heating) problems because the buildings on one or two sides became unoccupied or even knocked down making it an unplanned hear transfer surface.

I can get behind both sides - include or don't - which is why I ask.

Julien

Envoy? de mon iPhone

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It is an interior wall only if it is physically tied into the abutting wall.Much of the time there is an actual gap and even if it is 'enclosed' it will not be conditioned in the gap area ?and therefor is an exterior wall albeit may not see 'the most extreme' weather.

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I agree. If there is a gap, any gap, then I would consider it an exterior wall.

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

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Example 5-Q in the 90.1-2013 User?s Manual still uses both above-grade and below-grade walls as ?exterior walls? for determining gross wall area.

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

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The 'Standard Definitions of Building Geometry for Energy Evaluation'
technical report issued by NREL defines WWR as the ration of Wall
Fenestration Area and the Gross Above-Grade Wall Area.

Vinay Devanathan's picture
Joined: 2011-10-02
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David is correct regarding prescriptive compliance with Section 4 in 90.1. However, 2010 Appendix G in table G3.1.5 clearly states that baseline WWR is limited to 40% of ?gross above grade wall area?. This is an important distinction.
__________________________

Michael Rosenberg, CEM, LEED AP
Senior Research Scientist
ENERGY & ENVIRONMENT DIRECTORATE

Pacific Northwest National Laboratory
2032 Todd Street
Eugene, OR 97405
(509) 375-1995
michael.rosenberg at pnnl.gov
www.pnnl.gov

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The 90.1-2007 User?s Manual, example 5-K indicates the same rule.

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

www.wspgroup.com

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Unconditioned parking garage would not contribute to your WWR. Only
conditioned underground space should be counted.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

ASHRAE interpretation IC 90.1-2004-1 dated June 25, 2005 states that gross wall area is ?the area of the wall measured from the exterior face from the top of the floor to the bottom of the roof?.

It goes on to say that buildings with conditioned below-grade space, the gross wall area includes below-grade space.

Cheryl M. Saldanha, P.E. (CA)
Senior Staff I - Building Technology
SIMPSON GUMPERTZ & HEGER
212.271.7000 main
212.271.6962 direct
917.856.7702 mobile
212.271.0111 fax
www.sgh.com

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Page 213 of 90.1-2010 says ?above-grade?

Shaun

Shaun Martin LEED-AP, BEMP

Principal

Shaun Martin Consulting

#90 ? 425 Carrall Street

Vancouver, BC V6B 6E3

p. 604-789-1095

sm
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Expanding on Michael?s and Elizabeth?s comments?
Note that Appendix G. specifically refers to ?above-grade wall area? for determining fenestration percentages (in 2007, 2010 and 2013 versions).
Also note that ?parking garages with natural or mechanical ventilation are not considered enclosed spaces? per 90.1 definition of space. Therefore, any ?walls?, whether above or below-ground, are not part of the building envelope, are therefore not technically walls per 90.1 and wouldn?t be included in WWR calculations.

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

[cid:image001.jpg at 01D1074F.03C72A50] [cid:image009.jpg at 01D1074F.03C72A50]

134 South Fitzhugh Street Rochester, NY 14608

T: (585) 698-1956 F: (585) 325-6005

bbishop at pathfinder-ea.com www.pathfinder-ea.com

[http://png-5.findicons.com/files/icons/977/rrze/720/globe.png]Carbon Fee and Dividend - simple, effective, and market-based.

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But to further complicate things, my understanding is that if you have an enclosed-conditioned space within the parking garage (elevator lobby, maintenance room, etc), and walls of that space that border the unconditioned parking garage you WOULD count that as above-grade wall.

The most complicated scenario is a conditioned room tucked along the perimeter of the parking garage. In that case you WOULD COUNT the walls that separate the space from the unconditioned garage as part of the App G WWR calc, but you WOULD NOT COUNT the below grade walls that separate that space from dirt in the App G WWR calcs.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100
www.rushingco.com

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I have NEVER heard of WWR ratio including below grade walls. ?California Title 24 never has.

Sent from Yahoo Mail on Android

From:"Jones, Christopher"
Date:Thu, Oct 15, 2015 at 10:15 AM
Subject:[Bldg-sim] ASHRAE 90.1 Window to Wall area definition

I know this question has been asked before but I could not find a related thread.

?

90.1 states that the WWR is based on the gross wall area and the definition of gross wall area includes below ground walls as well as above ground walls..? Including the below grade walls can make a significant difference in the WWR for typical urban high rise buildings with a number of below grade parking floors.?

?

Can someone confirm that the WWR calculation is based on above grade wall area plus below grade wall area?

?

?

?

Christopher Jones, P.Eng.
Senior Engineer

?

WSP Canada Inc.

2300 Yonge Street, Suite 2300

Toronto, ON M4P 1E4
T +1 416-644-4226

F +1 416-487-9766

C +1 416-697-0056

?

www.wspgroup.com

?

You are receiving this communication because you are listed as a current WSP contact. Should you have any questions regarding WSP?s electronic communications policy, please consult our Anti-Spam Commitment www.wspgroup.com/casl. For any concern or if you believe you should not be receiving this message, please forward this message to us at caslcompliance at wspgroup.com so that we can promptly address your request. This message is intended only for the use of the individual or entity to which it is addressed, and may contain information which is privileged, confidential, proprietary or exempt from disclosure under applicable law. If you are not the intended recipient or the person responsible for delivering the message to the intended recipient, you are strictly prohibited from disclosing, distributing, copying or in any way using this message. If you have received this communication in error, please notify the sender, and destroy and delete any copies
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That is a great point. Appendix G is different from the prescriptive
requirements.

The prescriptive requirements (and thus Energy Cost Budget method) allow
you to count below-grade conditioned walls as per section 5.5.4.5 as part
of your "gross wall area", while Appendix G specifically says above-grade
walls only.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

You people rock. I got way smarter in 5 minutes of reading your posts than
5 hours of scouring references.

James V Dirkes II, PE's picture
Joined: 2011-10-02
Reputation: 203

So up here in Zone 6 and 7 where the first level of parking below grade is often heated enough to make it a conditioned space, one would count those below grade walls in the WWR for the Energy Cost Budget method. That can make a somewhat significant difference in how much glazing the baseline case has in the above grade walls.

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

www.wspgroup.com

Jones, Christopher's picture
Joined: 2015-06-11
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It would have to be heated enough to qualify per Table 3.1, which would be
pretty high:

[image: Inline image 1]

And then you would have to insulate it like a conditioned space (rather
than just a semi-heated space). But yes, then you could count it!

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

Anonymous's picture
Anonymous

Thanks Elizabeth,
Your reply brings up another question. If the proposed design meets the requirement of Table 3.1 does the baseline automatically follow suit? Or does one have to first construct the baseline case model to determine the self-sized heating capacity to determine if the space is conditioned or semi-heated? It sounds like it would be an iterative process ? first model the space with exterior insulation for a conditioned space then determine the heating capacity. If it shows a semi-heated space, then change the insulation and check again, and so on?

[cid:image003.png at 01D09C46.E75BA0D0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

www.wspgroup.com

Jones, Christopher's picture
Joined: 2015-06-11
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According to my understanding it would be based off the proposed.
Thanks Elizabeth,
Your reply brings up another question. If the proposed design meets the requirement of Table 3.1 does the baseline automatically follow suit? Or does one have to first construct the baseline case model to determine the self-sized heating capacity to determine if the space is conditioned or semi-heated? It sounds like it would be an iterative process ? first model the space with exterior insulation for a conditioned space then determine the heating capacity. If it shows a semi-heated space, then change the insulation and check again, and so on?

[cid:image001.png at 01D10759.6D80DAE0]
Christopher Jones, P.Eng.
Senior Engineer

WSP Canada Inc.
2300 Yonge Street, Suite 2300
Toronto, ON M4P 1E4
T +1 416-644-4226
F +1 416-487-9766
C +1 416-697-0056

www.wspgroup.com

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Whether you choose to build your baseline before/during/after your proposed
case, you will need to very actively reference the proposed/actual design
along the way to determine where the conditioned spaces lie (per the
glossary entries), and from there where the envelope line is drawn
separating the conditioned from the exterior/unconditioned/semi-conditioned
areas.

Insofar as the WWR discussion thread goes, I believe I?m situated in
Nathan?s camp. I simply (?) equate/read ?above-ground? in Appendix G to
mean ?not facing dirt,? regardless of where the grade lies.

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
306 N Ferrel

Olathe, KS 66061

office: 785.410.3317

www.catonenergy.com

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This discussion is very interesting and relates to another question I asked before, and since it didn't get much traction and this one did, please allow me to bring it up again.

For above grade walls that are abutting an existing building (adiabatic), do you include those in the WWR calculation or exclude them?

Thanks,
Julien

Envoy? de mon iPhone

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Another interesting question!

If you look at how ASHRAE 90.1 defines "exterior building envelope", as
being "the elements of a building that separate conditioned space from the
exterior space", then I would say that no, your adiabatic walls do NOT
contribute to your building envelope or your WWR, because they do not abut
exterior space. So you should exclude them from your calc.

*Elizabeth Gillmor PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091

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Anonymous

I agree, but can envision a few real-world cases where you might definitely
call the abutting walls part of the conditioned envelope, but would still
fall into the ballpark of ?a grey area:?

? What if the two abutting buildings aren?t sharing a wall, but
rather an enclosed unconditioned void/cavity?

? What if you aren?t comfortable calling it an adiabatic surface
(i.e. the adjacent building is unconditioned/unoccupied)?

I think I?d fall back on a ?gut check? in such instances: If it makes zero
sense to install glazing for any proposed case design, then you should feel
safe consistently excluding those surfaces from the resultant WWR
requirements on the baseline side. Put another way, don?t make the
baseline include windows where it?s completely unreasonable (this also
encompasses my ?facing dirt? litmus test).

I know that isn?t terribly black & white ? I wouldn?t be surprised if some
specific urban energy codes have tread these paths enough to address the
various possibilities for abutting buildings? (?)

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
306 N Ferrel

Olathe, KS 66061

office: 785.410.3317

www.catonenergy.com

*From:* Elizabeth Gillmor [mailto:elizabeth at energetics-eng.com]
*Sent:* Friday, October 16, 2015 3:32 PM
*To:* Julien Marrec
*Cc:* Nicholas Caton; Jones, Christopher; bldg-sim at lists.onebuilding.org
*Subject:* Re: [Bldg-sim] ASHRAE 90.1 Window to Wall area definition

Another interesting question!

If you look at how ASHRAE 90.1 defines "exterior building envelope", as
being "the elements of a building that separate conditioned space from the
exterior space", then I would say that no, your adiabatic walls do NOT
contribute to your building envelope or your WWR, because they do not abut
exterior space. So you should exclude them from your calc.

*Elizabeth Gillmor **PE, BEMP, LC, LEED AP*

*e n e r g e t i c s **consulting engineers, llc*

energetics-eng.com

c 303.619.0091

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Julien,

Wouldn?t a wall abutting to another wall that is conditioned on the other side make it an interior wall instead of an exterior wall? It?s effectively an addition to the other building.

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

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Keith,

It's an interesting point of view.

Different owners most of the time in my experience (happens all the time in NYC), the adjacent building is a black box in my opinion. Might or might not be occupied or conditioned to the same level now or 5 years from now, and you are likely to just be speculating about what's going on inside.

To some extend I might even be advocating to insulate these walls (though I'm guessing I'll have a hard time selling this to a developer)... I've seen enough existing buildings running into (heating) problems because the buildings on one or two sides became unoccupied or even knocked down making it an unplanned hear transfer surface.

I can get behind both sides - include or don't - which is why I ask.

Julien

Envoy? de mon iPhone

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It is an interior wall only if it is physically tied into the abutting wall.Much of the time there is an actual gap and even if it is 'enclosed' it will not be conditioned in the gap area ?and therefor is an exterior wall albeit may not see 'the most extreme' weather.

Sent from my T-Mobile 4G LTE Device

-------- Original message --------
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I agree. If there is a gap, any gap, then I would consider it an exterior wall.

Keith Swartz, PE | Senior Energy Engineer
Seventhwave | Madison.Chicago.Minneapolis
608.210.7123 seventhwave.org

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