[Equest-users] Above Roof Canopy Modeling

Shinn, Kim kim.shinn at tlc-eng.com
Thu Feb 18 07:55:43 PST 2010


Another possible issue on the cooling side:  In some climates, and in some building configurations, we see very high cooling loads in the fall, winter and spring (e.g, The Middle East).  Ambient temperatures moderate somewhat from summer extremes, but the low solar altitudes are throwing radiation load at the windows at a much more direct angle, frequently “under” the lip of our overhangs and canopies.

Kim E Shinn, PE, LEED AP BD+C, CxA
Senior Sustainability Consultant

From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Thursday, February 18, 2010 9:29 AM
To: reniel barroso; Shinn, Kim; Dakota Kelley; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Above Roof Canopy Modeling

Without more specifics, I think we can only give you some general advice/suggestions…  I haven’t tried this, but if you’re trying to observe results with/without the shade, maybe you should just delete the shade instead of altering transmittance and see if anything changes?

Overhangs/shades/canopies and the like can both help and hurt over the course of the year.  From what we’ve heard I don’t think you’re doing anything wrong in application.  I might take these results as a sign you need to carefully reconsider your canopy design with respect to how it is blocking sunlight.

Rather than focusing on overall cooling/heating energy spent, you might do well to identify which specific internal/external load components are changing significantly.  If you have any daylighting controls specifically, watch carefully what’s happening to your lighting energy spent.

The increase in heating energy is likely because you’ve eliminated a significant amount of solar gains through fenestrations and opaque walls by blocking the sun during heating months.  Remember that building shades are shading more than windows!

In the heating months and from an energy-perspective, a perfect window shade blocks only as much direct sunlight as is required to prevent glare issues through windows.  Any other direct light is welcome as a free heating source – both on windows and opaque walls.

The lesser increase in cooling energy probably has a less direct conglomeration of reasons…  That it’s relatively minor suggests it could be a lot of things.  I would look at whether your simultaneous cooling/heating hours are changing.  For review:  In cooling months, a perfect shade blocks (reflects away) direct light incident on windows and opaque walls to minimize solar thermal loads, but still lets indirect light inside windows for daylighting purposes without obstructing views to an unacceptable level.

Another potentially odd daylight/thermal behavior interaction I’ve observed:  If you end up really cutting down your lighting energy spent, you might observe a corresponding increase in heating energy spent, as you’re effectively eliminating a heating source in the winter by not running your lights at 100%.

~Nick
[cid:image001.jpg at 01CAB080.88F26590]

NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com

From: reniel barroso [mailto:renielbarroso at yahoo.com]
Sent: Thursday, February 18, 2010 6:27 AM
To: Shinn, Kim; Nick Caton; Dakota Kelley; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Above Roof Canopy Modeling

Hi!

Thanks for your replies.
It helps us a lot.

On the model that we're working on,
We already did what everyone suggested.
We modeled the canopy as fixed shading.

To double check if the model is running as what we're expecting based on cooling load fundamentals,
We modeled full opaque canopy (0 transmittance) and 1.0 transmittance for comparison purposes only.

After running the model, we had weird results:

0 transmittance
Chilled Water - 104.05 MBTU
Space Heating - 74.8 kwh (X000)

1.0 transmittance
Chilled Water - 109.9 MBTU
Space Heating - 96.2 kwh (X000)

Am I modeling it wrong?
Am I missing something?
Are we having the same results especially with the heating consumption?
What are the areas that I should check first before concluding?
Note that we modeled the systems for both as AUTOSIZING.

Thanks for your assistance.


Reniel



________________________________
From: "Shinn, Kim" <kim.shinn at tlc-eng.com>
To: Nick Caton <ncaton at smithboucher.com>; Dakota Kelley <dakotak at teliospc.com>; reniel barroso <renielbarroso at yahoo.com>; "equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org>
Sent: Wednesday, February 17, 2010 21:44:23
Subject: RE: [Equest-users] Above Roof Canopy Modeling
At the risk of piling on more information than you really wanted:

App G allows you to take advantage of shading – so, remove shading from your 90.1 baseline.

You can assign schedules, transparency and reflectance to shades.  If you want to model the effect of deciduous trees planted near the building, for instance, you can use a schedule to have greater transparency in the winter (for passive solar heating) and less transparency in the summer for shading.

Kim E Shinn, PE, LEED AP BD+C, CxA
Senior Sustainability Consultant

From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Wednesday, February 17, 2010 11:29 AM
To: Dakota Kelley; Shinn, Kim; reniel barroso; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Above Roof Canopy Modeling

Thanks Dakota!

This is good to know as I have a situation where it would probably be less work to explore some specific overhang/fin options within my complex eQuest model vs. trying to build a separate model through my more usual daylight analysis workflows.

Bonus points for your response being 10x more clear than my question =)!

~Nick

[cid:image001.jpg at 01CAB080.88F26590]

NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com

From: Dakota Kelley [mailto:dakotak at teliospc.com]
Sent: Wednesday, February 17, 2010 11:16 AM
To: Nick Caton; Shinn, Kim; reniel barroso; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Above Roof Canopy Modeling

Window shades only shade their parent window, not the walls.  Building shades will shade everything in their shadow, and they rotate with the building if the azimuth is changed.  Fixed shades also shade everything in their shadow, but they do not rotate with the building.


[cid:image002.jpg at 01CAB080.88F26590]                        DAKOTA KELLEY
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From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Wednesday, February 17, 2010 11:10 AM
To: Shinn, Kim; reniel barroso; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Above Roof Canopy Modeling

Here is another illustration shading a courtyard of sorts.  You’re looking at the dark grey rectangle in both examples.

I have a followup actually for others familiar with creating building shades – are they any different in behavior from a window shade, or are they the same thing simply defined in different ways?  More specifically, do window shades shade buildings and can I define building shades as a means of modeling multiple vertical fins/horizontal light shades per window?

[cid:image003.png at 01CAB080.88F26590]

~Nick
[cid:image001.jpg at 01CAB080.88F26590]

NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Shinn, Kim
Sent: Wednesday, February 17, 2010 9:03 AM
To: reniel barroso; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Above Roof Canopy Modeling

Reniel:

What you need is an exterior shade.

In detailed edit mode, go to Building Shell and select Fixed Shades (or a Building Shade, depending on whether you want the shade to be attached to the building – as it rotates, for instance).  A fixed shade remains fixed in space.  This is a good way to model adjacent buildings.

[cid:image004.png at 01CAB080.88F26590]

Right click on Fixed Shade and go through the dialog boxes.

Kim E Shinn, PE, LEED AP BD+C, CxA
Senior Sustainability Consultant

From: reniel barroso [mailto:renielbarroso at yahoo.com]
Sent: Wednesday, February 17, 2010 8:22 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Above Roof Canopy Modeling

Hi to All,

We are modeling 3 buildings interconnected with each other.
A large canopy is covering the roof of the buildings and partially shading the courtyard within these buildings.

Can we model this canopy in eQuest? How?
Can we model its effect on the cooling load of spaces facing the courtyard?
We are expecting that solar heat gain will be lower on fenestrations of the rooms/spaces facing courtyard due to shading compared to perimeter spaces facing outside the development.

Thanks in advance.


Reniel




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