[Bldg-sim] Above Grade External Wall Area Weighted U-value Calculation

Sherif Farag sherif.sabr at gmail.com
Mon Sep 30 09:42:59 PDT 2013


Jeremiah/ Nathan/ Joe/ Ralph/ and Mike;

Many thanks for your informative input, really appreciated;

Best Regards,

 

Sherif Farag

Senior Sustainability Consultant

P.O. Box: 127842

Abu Dhabi, UAE

M: +971 55 199 0022 | E:  <mailto:sherif.sabr at gmail.com>
sherif.sabr at gmail.com | Skype ID: sherif.farag9

 

From: Jeremiah Crossett [mailto:jcrossett at phasechange.com] 
Sent: Monday, September 30, 2013 8:13 PM
To: Nathan Miller
Cc: Sherif Farag; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Above Grade External Wall Area Weighted U-value
Calculation

 

You might find the report by morrison hershfield useful for researching
methodologies.
<http://www.morrisonhershfield.com/ashrae1365research/Pages/Insights-Publica
tions.aspx>
http://www.morrisonhershfield.com/ashrae1365research/Pages/Insights-Publicat
ions.aspx




 

 

Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions

120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951

www.phasechange.com <http://www.phasechange.com>  

    <http://i.imgur.com/Sldxf.jpg> 

 

 

 

 

On Mon, Sep 30, 2013 at 9:04 AM, Nathan Miller <nathanm at rushingco.com
<mailto:nathanm at rushingco.com> > wrote:

It isn't like the reviewer is making things up, I think it is pretty clear
from the language of 90.1 Appendix G that you have to account for these
exposed slab edges. Frankly 90.1-2007 is a little more forgiving, allowing
for area-weighted U-factors for the entire wall, I believe previous versions
of Appendix G (2004 for example) actually specifically required that you
model uninsulated assemblies as their own discrete wall types. See excerpts
below:

 

ASHARE 90.1-2007 Appendix G:


 

ASHRAE 90.1-2004 Appendix G:



We usually model the slab edges as separate walls (only about 1 foot high)
and make the other walls "shorter" when you take out this area. If you don't
do this in the wizard, you can set up a macro in the .inp to to it, but it
takes a bit of work. Frankly if you already have the model set up without
slab areas, it seems much easier to to do the weighted U-factor calculation.


 

Nathan Miller - PE, LEEDRAP 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> 

Our new web site:  <http://www.rushingco.com/> www.rushingco.com

 

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:bldg-sim-bounces at lists.onebuilding.org> ] On Behalf Of Sherif Farag
Sent: Sunday, September 29, 2013 9:32 AM
To: bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> 
Subject: [Bldg-sim] Above Grade External Wall Area Weighted U-value
Calculation

 

Dear All,

I have submitted a project for review and received a comment requesting me
to include the concrete slabs between floors (Not drop beams) in the
External Wall' area weighted U-value calculation, the reviewer believes that
concrete slabs acts as a thermal bridge and should be insulated from the
outer side (The slab thickness), my understanding that concrete slab
shouldn't be regarded as a part of the occupied area and therefore shouldn't
be included in the area weighted U-value calculation.

I would appreciate if you can advise on the above query!

Thanks & Best Regards,

 

Sherif Farag

Senior Sustainability Consultant

P.O. Box: 127842

Abu Dhabi, UAE

M: +971 55 199 0022 <tel:%2B971%2055%20199%200022>  | E:
sherif.sabr at gmail.com <mailto:sherif.sabr at gmail.com>  | Skype ID:
sherif.farag9

 

 


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