[Equest-users] Slab extending through wall
Bruce Easterbrook
bruce5 at bellnet.ca
Wed Nov 6 05:45:20 PST 2013
I would think the effect of the balconies would increase the thickness
of the exterior laminar layer on the building. The air flow is
perpendicular to the fins. In calm conditions the main driver is going
to be stack effect. The exposed edges are on a flat surface and would
have a normal boundary layer. Without a projection they would offer
little resistance to the airflow from the stack effect.
A 60% reduction in effective R-value for a building is quite a
significant effect depending on where you are starting from. A high
ratio glass building is a low starting point.
Bruce Easterbrook P.Eng.
Abode Engineering
On 05/11/2013 05:25 PM, Robby Oylear wrote:
> It surprises me that the report indicates a better R-value for the fin
> effect of a concrete balcony vs. the simplified exposed slab edge
> approach. Seems to violate the basic teachings heat transfer 101. I
> can't think of a logical explanation of how that could be the case and
> would chalk it up to intricacies of the modeling tool. However I
> agree with Nathan that since the report doesn't show nearly any
> difference between the fin effect vs. the exposed slab edge that it's
> not necessarily worth the complication in modeling unless the balcony
> slabs are the focus of the study.
>
>
> On Tue, Nov 5, 2013 at 2:00 PM, Nathan Miller <nathanm at rushingco.com
> <mailto:nathanm at rushingco.com>> wrote:
>
> Kapil,
>
> No, I am only accounting for the "face" of the balcony, as if you
> sheared it off at the plane of the wall.
>
> That is my point, the fancy thermal modeling in the report, which
> is supposed to account multi-dimensional fin-effects doesn't come
> out with much different result than if you just take a simplified
> approach like a typical UA-trade-off calculation (one directional
> heat transfer, no fin effects accounted for). So by that line of
> reasoning, you would likely be OVER ESTIMATING heat loss if you
> throw in all three heat-exchanger surfaces that you mention in
> your methodology. I'd be interested if you compared your
> calculation results to the thermal modeling in the report if you
> feel like a little intellectual exercise.
>
> *Nathan Miller **-****PE, LEED^® AP BD+C, CEM*
>
> /Mechanical Engineer/Senior Energy Analyst /
>
> *RUSHING*| *D*206-788-4577 <tel:206-788-4577> |*O*206-285-7100
> <tel:206-285-7100>
>
> *www.rushingco.com <http://www.rushingco.com/>***
>
> *From:* Kapil Upadhyaya [mailto:KapilU at kirksey.com
> <mailto:KapilU at kirksey.com>]
> *Sent:* Tuesday, November 05, 2013 1:53 PM
> *To:* Nathan Miller; Bishop, Bill; David Griffin; 'Coleman,
> Kevin'; equest-users at lists.onebuilding.org
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* RE: [Equest-users] Slab extending through wall
>
> Nathan,
>
> In the Balcony calculation, are you accounting for both the
> 'edges' and 'exposed area' of the balcony ?
>
> In my opinion, a concrete balcony should be accounted for as a
> heat exchanger with 3 surfaces (perimeter edges, upper surface,
> lower surface); it looks like you are only accounting for the edges.
>
> I had a 'heated' discussion about this with a vendor recently and
> the above is more or less a conclusion of that. Some of the
> structural thermal break products can be too expensive to justify
> based on energy savings, if area of balconies is not accounted
> for; the bigger your balcony, the better your payback from thermal
> breaks.
>
> Best,
>
> *Kapil Upadhyaya, LEED AP*
> Associate
>
> *Kirksey* | Architecture
> 6909 Portwest Drive | Houston Texas 77024 |www.kirksey.com
> <http://www.kirksey.com>
> o 713 426 7508 <tel:713%C2%A0426%C2%A07508> | f 713 850 7308
> <tel:713%C2%A0850%C2%A07308> |kapilu at kirksey.com
> <mailto:kapilu at kirksey.com>
>
> *2012-2013 Firm of the Year *
> Texas Society of Architects
>
> *From:*Nathan Miller [mailto:nathanm at rushingco.com]
> *Sent:* Monday, November 04, 2013 5:27 PM
> *To:* Bishop, Bill; David Griffin; 'Coleman, Kevin';
> equest-users at lists.onebuilding.org
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* Re: [Equest-users] Slab extending through wall
>
> To me the most interesting part of the report isn't the conclusion
> that thermally broken balconies and slab edges give significantly
> better thermal performance (we all know that intuitively). Instead
> it gives a way of back checking what I would consider to be
> "standard practice" for calculating area-weighted U-factor for
> these same assemblies using default ASHRAE U-values to
> sophisticated thermal model results. Here are my thoughts,
> checking my calcs and comments appreciated.
>
> *Executive summary: It looks like our standard assembly
> performance tables and area-weighted U-factor calculations get us
> "close enough" to the results from this report that it doesn't
> seem to suggest we should switch methodologies. *
>
> **
>
> *Comparison calculation for steel-framed walls (stud insulation +
> exterior rigid):*
>
> For a 16" OC metal stud wall, R-12 Batt cavity insulation and R-5
> continuous rigid insulation, the report states that the Effective
> R-value for the wall + slab will be R-7.4.This is based on 8'8"
> floor-to-floor, and 8" slab.
>
> Using ASHRAE 90.1-2007 Table A3.3 for steel framed walls, we would
> get an effective U-factor for the wall portion of U = 0.0785
> (interpolating between the R-13 + R-11 batt values). If we use
> Table A3.1A for the exposed slab edge (assuming 8" normal weight
> solid concrete walls), we get a U-factor of U = 0.740 for the slab
> edge.
>
> Doing an area weighted U-factor calc: U_eff = U_1 *A_1 +U_2 *A_2
> /(A_1 +A_2 ) or in this case, factoring out the Length of the wall
> section we use: U_1 *H_1 +U_2 *H_2 /(H_1 +H_2 ) = (0.0785*8 +
> 0.740*8/12)/(8+8/12) = 0.1294 or an effective R-value of 7.73,
> which is pretty close to the R-7.4 claimed, a difference of about
> 4% in U-value. Maybe I'm cynical, but to me that seems close enough.
>
> I only spot checked this assembly, so maybe there is more impact
> with different construction types.
>
> Another interesting tid-bit: Apparently the much vaunted
> fin-effect is actually pretty minimal. If you look at the results
> of the exposed slab-edge condition vs the full balcony fin-effect,
> the balcony scenario actually shows slightly BETTER thermal
> performance. Odd.
>
> *Nathan Miller **-****PE, LEED^® AP BD+C, CEM*
>
> /Mechanical Engineer/Senior Energy Analyst /
>
> *RUSHING*| *D*206-788-4577 <tel:206-788-4577> |*O*206-285-7100
> <tel:206-285-7100>
>
> *www.rushingco.com <http://www.rushingco.com/>***
>
> *From:* equest-users-bounces at lists.onebuilding.org
> <mailto:equest-users-bounces at lists.onebuilding.org>
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of
> *Bishop, Bill
> *Sent:* Monday, November 04, 2013 1:42 PM
> *To:* David Griffin; 'Coleman, Kevin';
> equest-users at lists.onebuilding.org
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* Re: [Equest-users] Slab extending through wall
>
> Here's a timely report on effective R-values of assemblies with
> slab/balcony thermal bridges:
>
> The Importance of Slab Edge and Balcony Thermal Bridges
> <http://www.rdhbe.com/database/files/library/Balcony_and_Slab_Edge_Thermal_Bridges___1___R_values_and_Energy_Code_Canada__Sept_24_13.pdf>
>
> Regards,
>
> Bill
>
> *William Bishop, PE, BEMP, BEAP, LEED AP **|**Pathfinder Engineers
> & Architects LLP*
>
> *Senior Energy Engineer*
>
>
>
> webCertified_logo_colorRGB72DPI.jpg
>
> 134 South Fitzhugh StreetRochester, NY 14608
>
> T: (585) 325-6004 <tel:%28585%29%20325-6004> Ext. 114F: (585)
> 325-6005 <tel:%28585%29%20325-6005>
>
> bbishop at pathfinder-ea.com
> <mailto:wbishop at pathfinder-ea.com>www.pathfinder-ea.com
> <http://www.pathfinder-ea.com/>
>
> PSustainability -- the forest AND the trees.P
>
> *From:*equest-users-bounces at lists.onebuilding.org
> <mailto:equest-users-bounces at lists.onebuilding.org>
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of
> *David Griffin
> *Sent:* Monday, November 04, 2013 4:20 PM
> *To:* 'Coleman, Kevin'; equest-users at lists.onebuilding.org
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* Re: [Equest-users] Slab extending through wall
>
> Kevin,
>
> I'm fairly sure eQUEST is not even going to closely approximate
> the heat loss/gain accurately unless you dial the loads in
> manually which means you have to calculate them by hand first. I
> suggest referring to ASHRAE-D-RP-1365 for guidance on estimating
> the loads. The section you are interested in starts on page 35.
>
> Thanks,
>
> **
>
> *David W. Griffin II*
>
> Energy Analyst
>
> ETC Group, LLC
>
> 801-278-1927 x 128 <tel:801-278-1927%20x%20128>
>
> Cell 480-736-2945 <tel:480-736-2945>
>
> dgriffin at etcgrp.com <mailto:dgriffin at etcgrp.com>
>
> www.etcgrp.com <http://www.etcgrp.com>
>
> Copy of ETC_LogoOnly2_rgb_sm.png
>
> *Energy Engineering for a Sustainable Future*
>
> 1997 South 1100 East, Salt Lake City, UT 84106-4471
>
> -------------------------------------------------------------------------------------------------------------------
>
> CONFIDENTIALITY NOTICE This e-mail transmission, and any
> documents, files or previous e-mail messages attached to it may
> contain confidential information that is legally privileged. If
> you are not the intended recipient or the person responsible for
> delivering it to the intended recipient, you are hereby notified
> that any disclosure, copying, distribution or use of any of the
> information contained in or attached to this transmission is
> strictly prohibited. If you have received this transmission in
> error, please immediately notify us by telephone at (801) 278-1927
> <tel:%28801%29%20278-1927> and destroy the original transmission
> and its attachments without reading them. Thank you.
>
> *From:*Coleman, Kevin [mailto:kcoleman at nexant.com]
> *Sent:* Monday, November 04, 2013 11:56 AM
> *To:* equest-users at lists.onebuilding.org
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* [Equest-users] Slab extending through wall
>
> I am evaluating a new 10-story hotel design that is proposing
> glass curtain walls and pre-tensioned concrete floors that project
> beyond the walls. On 3 sides the projections are minimal (6
> inches). However, on one side, the projections extend about 3 ft.
>
> For the small projections, I intent to use the following method
> recommended in the thread below. "In screen 4 of 25 of the DD
> shell wizard you can specify "Slab Penetrates Wall Plane" (check
> box)."
>
> I am interested in any tips for modeling the thermal impacts of
> the larger projections. Thoughts? (I plan to use window shading
> for the light/shading impacts.)
>
> I am hopeful that the analysis will help convince the design team
> to incorporate some insulation and thermal breaks!
>
> Thanks in advance!
>
> Kevin
>
> Brian Fountain bfountain at greensim.com <http://greensim.com>
>
> Mon Dec 6 11:45:18 PST 2010
>
> Previous message: [Equest-users] balcony
>
> Next message: [Equest-users] Shading
>
> Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
>
> In screen 4 of 25 of the DD shell wizard you can specify "Slab
>
> Penetrates Wall Plane" (check box). If you do, eQUEST created a new
>
> wall type of height equal to your slab thickness and composed of
> 1' of
>
> concrete plus any slab edge insulation you specify on the same wiz
>
> screen. That provides a parallel path for the heat transfer from
> the
>
> balcony or slab edge. Not exactly 2D heat transfer modelling --
> but at
>
> least you aren't ignoring the effect of the slab edge or balcony.
>
> *Kevin Coleman, CEM, LEED AP*?*Project Manager **?****Nexant,
> Inc.****?** Demand Management *
>
> 1232 Fourier Drive, Suite 125?Madison, WI 53717 ?608.824.1230
> <tel:608.824.1230> ?_kcoleman at nexant.com <mailto:kcoleman at nexant.com>_
>
> P Please consider the environment before printing this email**
>
>
> _______________________________________________
> Equest-users mailing list
> http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
> To unsubscribe from this mailing list send a blank message to
> EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
> <mailto:EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG>
>
>
>
>
> _______________________________________________
> Equest-users mailing list
> http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
> To unsubscribe from this mailing list send a blank message to EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131106/fffc3174/attachment-0002.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 161932 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131106/fffc3174/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/png
Size: 130868 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131106/fffc3174/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 3124 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131106/fffc3174/attachment-0004.jpeg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1559 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131106/fffc3174/attachment-0005.jpeg>
More information about the Equest-users
mailing list