[Bldg-sim] Balcony Heat Loss

Bishop, Bill wbishop at pathfinder-ea.com
Fri Jun 17 07:42:28 PDT 2011



Uninsulated assemblies are discussed in the User's Manual for ASHRAE
Standard 90.1. Page G-14 of 90.1-2010 User's Manual suggests:

"It is acceptable to model [projecting balconies] as having the depth of
the exterior wall they penetrate. For example, if the wall between the
intermediate floor slabs has a total depth of 8 in. (203mm), then these
assemblies can be modeled as being 8 in. (203 mm) thick. If the concrete
slab that forms the projecting balcony or intermediate floor slab for a
particular floor is 9 in. (229 mm) thick, then this section of the all
would be modeled in the proposed design as a 9 in. (229 mm) high
uninsulated concrete wall that is 8 in. (203 mm) thick."







From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Brian
Sent: Friday, June 17, 2011 10:39 AM
To: Aaron Smith
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Balcony Heat Loss


The accepted workaround is to add another wall type that is comprised of
12" of just concrete (U = 5.5 W/sq-m C) and has a height equal to your
slab thickness -- say 6".  So the area would be the wall length x the
slab thickness.

Not sure if this is clear -- it is better described on page 7-9 of the
EE4 modelling guide.


On 6/17/2011 10:20 AM, Aaron Smith wrote: 



When performing energy modeling to determine compliance with the
Canadian Energy Code (MNECB), penetrations through the building envelope
must be taken into account when calculating wall R-values if their area
exceeds 2% of envelope area.  I'm working on a LEED project and trying
to calculate the wall R-value of a Hotel taking into account heat losses
from the balconies which are extensions of the floor slab (balcony
penetrations exceed 2% of envelope area).


I realize this is a rather complex heat transfer problem but hope there
may be an easy approximation.  My first thought was to treat them like a
parallel path heat transfer problem: 1/Req = %slab/Rslab + %wall/Rwall
but I'm thinking that may not be fair (perhaps this would be used if you
had concrete studs in the wall).  My other thought is to treat the slab
penetrations as a separate wall type (uninsulated concrete wall) - this
would have a reduced affect on the overall wall R-value.  


Does anyone have thoughts on this?





Aaron Smith, P.Eng 

LEED(r) AP BD+C, M-ASHRAE, Mechanical Engineer


t: (902) 422-7393

f: (902) 423-4945

e: asmith at mreng.ca <mailto:asmith at mreng.ca> 


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