[Equest-users] Spandrel Glass

David Eldridge DEldridge at grummanbutkus.com
Sat Dec 8 10:42:38 PST 2018

Some of the mixup might be that some walls are for sake of argument in round figures 50% spandex and 50% vision glass, and some minor percent structure and other.

Other buildings might 33% structure/masonry/etc and 33% spandrel, and 33% vision glazing.

So a common approach in case a is spandrel = wall, windows are windows.

For case B you need two different walls, plus windows in one or both, and how you model the two walls may be important to your zone loads, but look odd in the rendering even if it is thermally equivalent and geometrically expedient.

If you have a photo of the facade you are talking about it might help to sync all of us.

DSE Mobile

On Dec 8, 2018, at 10:40 AM, Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>> wrote:

I'd like to thank every for their comments. I don't understand how the spandrels can be modeled as exterior walls since the exterior walls have a different u-factor and eQuest does not allow me to draw an exterior wall over an existing.  I think I understand Nick's approach, but it seems that the spandrels are not placed in the appropriate location and will influence the angle of solar gain?

To further complicate matters, this 5 story building does not have a plenum ceiling, the floor deck above is visible in the space below.

I was able to successfully model the spandrels by using a different type of glass, then entering the U-factor by the simplified method and zeroing the Sc and reflectance.  The problem is that LV-D  reports the spandrels as part of the glass, so it throws the window to wall ration calculations off.

I found the simplest method was simply remove the spandrels (+100) and run the LV-D report to get the actual area of the vision glass.


Paul Diglio
87 Fairmont Avenue
New Haven, CT 06513


From: David Griffin II <DGriffin at archnexus.com<mailto:DGriffin at archnexus.com>>
To: Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>>; David Eldridge <DEldridge at grummanbutkus.com<mailto:DEldridge at grummanbutkus.com>>; "jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>" <jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>>; Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>>; "equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>" <equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>>
Sent: Friday, December 7, 2018 5:18 PM
Subject: RE: [Equest-users] Spandrel Glass

I second Nick’s approach to spandrel. I have not thought to use the plenum as a geometry generator. I’ll have to utilize that next time.

By code, spandrel is considered a wall construction that happens to have glass in it rather than a window you can’t see through. In my mind, that justifies using a wall construction and adjusting the exterior surface reflectance accordingly rather than try and model it as a window.

I hope everyone is having a great holiday season!

[ARCH | NEXUS]<http://www.archnexus.com/>
2505 E Parleys Way
Salt Lake City, UT 84109
Office 801.924.5028


From: Nicholas Caton [mailto:Nicholas.Caton at schneider-electric.com]
Sent: Thursday, December 6, 2018 7:09 PM
To: David Eldridge <DEldridge at grummanbutkus.com<mailto:DEldridge at grummanbutkus.com>>; jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>; Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>>; equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>
Subject: Re: [Equest-users] Spandrel Glass

I’ll toss some extra thoughts/experience into the pile:

My preferred approach to handling large amounts of spandrel glass is to start by taking advantage of the wizards’ capacity to generate separate “plenum” exterior wall sections (of height resulting from your ceiling inputs), to produce equivalent area to the spandrel glass on each orientation.  Those separate sections are in part a by-product of the intent to distinguish the conditioned space/zone volume relative to the floor-to-floor height, but we can repurpose them!

I do not create glass on those “plenums” wall sections, but rather just make a new “spandrel” exterior wall construction in detailed mode and use custom user default expressions to automate assigning “spandrel” vs. “normal” constructions to each exterior surface as a function of their Z coordinate (0 = normal wall, else spandrel construction).

This can be combined with post-wizard manipulation of interior space/ceiling heights (which do not have to line up with the “seams” separating plenum from normal walls), to capture cases where the spandrel actually extends below the ceiling line and ensure the conditioned volume is accurate around your perimeters.  Be mindful that if the spandrel glass is largely incident on the conditioned volume it may be more appropriate to move them off the plenum spaces and onto the occupied spaces.

There is an aesthetic “downside” to this approach to consider (according to some industry professionals I’ve worked with), but if someone *really* wants a pretty 3D model picture that looks like a fishbowl from the likes of eQuest (?), I’ll just add that you can generate some (apparently convincing) “forgery” of extra windows by mis-using MSPAINT – the duct tape of my graphical tool belt.  And yes, I sleep at night just fine, thank you.

@David:  I’m not sure about that library entry either, but I have in the past been convinced myself it was okay to use the simplified window glass definition option and

  *   specify a shading coefficient of zero (where SC is the ratio of solar energy transmitted relative to single pane float glass), and
  *   specify a U-value appropriate to the degree of insulation (though I’d leave this equivalent to the underlying glass layer(s) if it’s just painted panels – run into that a couple times).

This modeling approach doesn’t pick up on all of the actual nuances of radiative* emissivity for painted-over windows, but it has for me been good enough for (literally) government work where there were much bigger problems to focus the energy model’s development around… If anyone has developed further best practices for handling “high-e coatings” applied to mitigating unwanted transmissive solar gains, I am certainly all ears =).


Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

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

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


From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of David Eldridge via Equest-users
Sent: Wednesday, December 05, 2018 5:59 PM
To: jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>; Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>>; equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>
Subject: Re: [Equest-users] Spandrel Glass

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Paul – to answer your question: painfully? It may not be that bad actually – what’s your base wall type? For a curtain wall that is half spandrel and half vision glass, make the exterior opaque surface equivalent to the spandrel sections as a defined opaque wall construction, and then add the vision glass to that – if you change the surface constructions in spreadsheet view it may not be that painful after all. The painful part will be deleting all of the current spandrel sections that are now defined as the base wall.

JRA – I’m not sure of the purpose of the spandrel glass type in the library, I don’t know if that window object model has the capability to perform as if it were an opaque surface although this spandrel glass definition may be available to be selected…I’m not sure it would be an accurate choice. I wonder if it is a research entry that isn’t meant for the modeling public. Anyone used it?


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach via Equest-users
Sent: Wednesday, December 05, 2018 5:39 PM
To: Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>>; Paul Diglio via Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>; equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>
Subject: Re: [Equest-users] Spandrel Glass


As I recall there IS a wall component called spandex glass in the Library. See if that solves your need.

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On Wed, Dec 5, 2018 at 3:33 PM, Paul Diglio via Equest-users
<equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>> wrote:
I have a building with a very large amount of spandrel glass panels, which I modeled as glass since this seemed to be the only way to insert the panels into the exterior walls.

I would somehow like to re-assign the spandrel panels as another exterior component so they will be counted as part of the exterior walls in the LV-D report instead of glass.

Any idea on how this can be done?

Thank you,

Paul Diglio
87 Fairmont Avenue
New Haven, CT 06513
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