[Equest-users] window replacement
Sami, Vikram
Vikram.Sami at perkinswill.com
Tue Aug 24 09:52:31 PDT 2010
Ben,
I would first go back to your base model and examine what percentage of the building load is actually coming from the glass. Your LS-C reports will give you your peak load components, and LS-F will give you your Monthly load components - a better indicator of overall energy usage.
Keep in mind this doesn't factor in ventilation loads. You will need to look at the SS-D report to get an overall picture of the loads your system sees, and work backwards from that to get a picture of what the ventilation component is. So for example - if your LS-C shows a peak cooling load of 1000kBTU/hr and your SS-D Shows 1500 kBTU/hr, then your ventilation loads will be 500 kBTU/hr. [eQUEST users - please correct me if I'm wrong here]
So if your glass conductance + Solar is 15% f the overall load, then a 5% savings is pretty significant, however, if its 50% of the load, then there might be a problem with your model.
Hope this helps
Vikram Sami, LEED AP
Sustainable Design Analyst
1382 Peachtree St. NE, Atlanta, GA 30309
t: 404-443-7462 f: 404.892.5823 e: vikram.sami at perkinswill.com www.perkinswill.com<http://www.perkinswill.com/>
Perkins+Will. Ideas + buildings that honor the broader goals of society
-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Ben Pressman
Sent: Tuesday, August 24, 2010 12:21 PM
To: equest-users at lists.onebuilding.org
Cc: Justin Murray
Subject: [Equest-users] window replacement
Thanks, Carol, for your quick response. I think my question might have
been too specific. My baseline model agrees to within 5% of the actual
gas and electric bills for the building. The exterior walls, especially
north and south elevations, are about 30% windows by area. By replacing
single-paned windows with double-paned, modern windows, I am expecting
about a 23% reduction in energy usage based on simple heat equation
estimations. eQuest is only returning a 5% savings. I suspect I am not
defining the replacement windows correctly, but it seems there must also
be a problem with how eQuest is calculating my heating loads through the
windows. I specified the windows' estimated percent wall area, and also
drew custom windows everywhere to match what the actual building looks
like. What is the best way to approach solving this problem?
Thanks again,
Ben
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