[Equest-users] Curtain wall system - how to model baseline?

Thu Jul 28 10:12:29 PDT 2016

Spandrel (opaque) sections of curtainwall are “walls” in both proposed and baseline cases as far as 90.1 terminology is concerned.  Consider them as such for determining both Proposed and Baseline case WWR’s.

In my past year of experience, similar to Nathan, I’ve dealt with many “fishbowl” buildings which appear all (or mostly) glass from the outside but typically have at least few feet of insulated envelope on the interior perimeter, so in that case it’s literally a wall construction with the outermost layer being glazing (or airspace then glass). 

Be sure to dig up any relevant envelope sections/details to carefully draw the line between “opaque” and “not opaque.”

~Nick

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael Campbell via Equest-users
Sent: Thursday, July 28, 2016 11:12 AM
To: Nathan Miller
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Curtain wall system - how to model baseline?

Thanks for the response Nathan.

There will be some spandrel glass, but I'm not sure how much.

But basically the spandrel portion would be considered a wall in the baseline.

Only the transparent window assemblies would be considered in the WWR.  Is that correct?

Thank you,

Mike 

On Thu, Jul 28, 2016 at 11:53 AM, Nathan Miller <nathanm at rushingco.com> wrote:

Would there really be no opaque portions (aka spandrel) of the curtain wall? At the very least I’d expect you’d have about a 1’ high slab-edge-bypass opaque section. 

Our curtainwall projects (resi and office) typically have 40-50% vision glazing, and the rest is opaque, and gets modeled as a wall with calculated U-factor depending on the spandrel + inboard insulation configuration. 

Nathan Miller, PE, LEED AP BD+C – Mechanical Engineer/Senior Energy Analyst

RUSHING | D 206-788-4577 | O 206-285-7100

www.rushingco.com <http://www.rushingco.com/> 

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael Campbell via Equest-users
Sent: Thursday, July 28, 2016 11:51 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Curtain wall system - how to model baseline?

Hello,

I have a potential project in which the client is proposing a curtain wall system.

The model will be based on ASHRAE 90.1-2013 Appendix G.

I believe the appropriate way to model this would be to have a WWR of 100% (or near 100%) in the proposed case.  For the baseline case, the window area would have to be reduced to get the WWR down to 40%.

Is this the correct way or is there different guidance for modeling curtain wall systems?

Thank you,

Mike Campbell

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