[Bldg-rate] FW: fenestration area requirement according to ASHRAE5.

Keith Swartz kswartz at ecw.org
Tue Sep 30 08:00:04 PDT 2008



I had to deal with this question a few months ago. The LEED NC 2.2
manual for EA Prerequisite 2 has two options for complying with the
second requirement. You could meet the prescriptive requirements
(Sections 5.5, etc.) OR meet the performance requirements (Section 11)
of ASHRAE 90.1-2004. If you can't meet the prescriptive requirements
(like 50% window-to-wall ratio), then the Section 11 model is an option.
Note that this model is different than the model for Credit 1, which
uses Appendix G. The window-to-wall ratio is limited to 50% for the
baseline building in the Section 11 model and limited to 40% for the
baseline building in the Appendix G model. The proposed building would
have the actual windows in both models.



Keith Swartz, PE, LEED(r) AP
Energy Engineer / Senior Project Manager
Energy Center of Wisconsin
455 Science Drive, Suite 200
Madison, WI 53711

Phone: 608-238-8276 ext. 123, Fax: 608-238-0523
<http://www.ecw.org> www.ecw.org  The Energy Center of Wisconsin is a
nonprofit organization that seeks solutions to energy challenges.


From: bldg-rate-bounces at lists.onebuilding.org
[mailto:bldg-rate-bounces at lists.onebuilding.org] On Behalf Of Dr. Dirk
A. Schwede
Sent: Monday, September 29, 2008 3:20 AM
To: bldg-rate at lists.onebuilding.org
Subject: [Bldg-rate] fenestration area requirement according to




we were asked to check the requirements for LEED NC EA P2 "Minimal
Energy performance" for a building in Berlin, Germany. The requirement "Vertical Fenestration Area" of the ASHRAE 90.1 code says that
the total vertical fenestration area shall be less than 50% of the gross
wall area, section 5.2.1 even says that 50% vertical fenestration area
shall not be exceeded for each space conditioning category.


Although we are aware that smaller windows are better for the buildings
energy balance, this "simple" requirement was much discussed between us,
as it would easily disqualify many modern buildings to comply with LEED
requirements and even with the ASHRAE Standard. ASHRAE alone would allow
using the trade-off path, however LEED requirements (Version NC 2.2)
demand compliance with section 5.5 of the ASHRAE Standard alone and does
not allow the trade-off option to be used.- Do I read the code
correctly, or is there a way to achieve LEED certification for buildings
with a fenestration area larger than 50%?  


Best Regards,

Dirk Schwede 




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