[BLDG-SIM] Simulations Insensitive to Glass Changes

[Taylor, Russell D UTRC]

Brandon,
 
The first thing that I would do is open up the SIM file and look at the
LS-C report (Building Peak Load Components). This report tells you what
the total building envelope loads and internal heat gains are for peak
cooling and heating conditions. Here are the categories provided:
 
WALL CONDUCTION

ROOF CONDUCTION

WINDOW GLASS+FRM COND

WINDOW GLASS SOLAR

DOOR CONDUCTION

INTERNAL SURFACE COND

UNDERGROUND SURF COND

OCCUPANTS TO SPACE

LIGHT TO SPACE

EQUIPMENT TO SPACE

PROCESS TO SPACE

INFILTRATION 

Since your building appears very insensitive to changes in glazing
U-value my guess is that this report will show that "WINDOW GLASS+FRM
COND" is small compared to the other loads or that one of these other
loads is much larger than the rest. This result may be correct,
especially if the gazing fraction of the facade is low. However, if
"UNDERGROUND SURF COND" is the largest conduction load then you may need
to set U-EFFECTIVE for the slab floors (reasonable values are between
0.01 and 0.02). 
 
You may also find that the building is much more sensitive to changes in
window solar heat gain coefficient than changes in U-value.
 
Russ Taylor

________________________________________________________________________
_______ 

Russell D Taylor, Ph.D. 
UTRC | 411 Silver Lane, MS 129-85 | East Hartford, CT 06108 | Ph: (860)
610-7485 
________________________________________________________________________
_______ 

 

________________________________

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Brandon
Nichols
Sent: Monday, July 23, 2007 5:10 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Simulations Insensitive to Glass Changes


All,
 
I have a 3-story historic building, with circa-1920's windows on all
four exposures.  Big, beautiful, clear-glass single-pane architectural
masterpieces.  So while doing an optimization study, it became apparent
to me that substantially changing the U-value and infiltration
coefficients was having very little effect at all on the loads.
 
For example, varying the U-value from 1.27 to 0.55, 0.45 and at last
0.30 in the parametric runs using the 'simplified method' produced a
0.5% total (over all runs) change in the total energy consumption.
Selecting representative glass types using the 'library method' produced
essentially equivalent.  Superimposing upon either of these a change in
the infiltration coefficient from 1/4" to 1/8" to 1/16" to 1/32"
produced no additional effect at all (the INF-METHOD = CRACK keyword is
specified) on the annual energy consumption.
 
Lastly, I changed the baseline glass to "unglazed opening", again with a
mystifying zero net effect on the overall energy consumption.  It's as
if the glass is not being calculated at all, but I see no errors or
warnings in the SIM file.
 
Anyone have an idea on how to debug this?
 
Thanks in advance...
 
 
Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS

600 Stewart Street

Suite 1000

Seattle, WA 98101

www.hargis.biz

 

d | 206.436.0400  c | 206.228.8707

o | 206.448.3376  f  | 206.448.4450

 
 

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