[Trace-users] Variable Shading Coefficient

[Hintz, Scott Fredrick. (KSC-ISC-4013)[URS Federal Technical Services, Inc.]]

Phil,

The short answer is TRACE is not setup (directly) to model SRT’s. Creating a custom internal shading library member and a custom internal shading schedule that utilizes the reset and lockout table is a possibility. The reset and lockout table would allow you to modify the load based on hourly OADB, but not directly based on glazing temperature.

Scott Hintz
CEM, LEED-AP BD+C, BEMP

Energy Engineer
Sustaining Systems Engineering (SSE)
[cid:image001.png at 01CC356F.49419AE0] Federal Technical Services
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From: Phil_Grossman at URSCorp.com [mailto:Phil_Grossman at URSCorp.com]
Sent: Monday, June 27, 2011 2:29 PM
To: trace-users at lists.onebuilding.org
Subject: [Trace-users] Variable Shading Coefficient


I have a 230,000 square feet, 400 room office building currently modeled in Trane Trace.  Fifty percent of the building’s exterior envelope is windows. The solar heat gain coefficient (SHGC) for the windows is currently modeled as a constant.  The goal is to use this model for LEED V3.0, EA Credit 1 - Optimize Energy Usage.

The actual windows installed in the building are sunlight responsive thermochromic (SRT).  With SRT windows their SHGC changes as the intensity of incident solar radiation changes.   The SHGC is at minimum when the sun’s intensity is greatest.  When the window’s temperature is  77 ° F the SHGC is 0.29 at 149 ° F the SHGC is 0.18.  More information about this product is available at www.pleotint.com<http://www.pleotint.com>.

It is my understanding that eQUEST  V3.55 can model variable tint windows based on total incident solar radiation, transmitted solar radiation or outdoor temperature.  Since the building is already modeled in Trace totally changing to eQUEST is considered impractical.

I would like to know your experience and/or thoughts on how this building can be modeled with the SRT windows, preferably in Trace or possibly some combination of Trace and eQUEST.  The model needs to be accurate, acceptable to the LEED reviewer, and consume as little of my time as possible.

Thank you in advance for your assistance.

Phil Grossman, PE, LEED®AP, HFDP
Senior Mechanical Engineer

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