[Equest-users] Difficult roof

[Nick Caton]

I agree: a 2-surface gable roof shape as John is demonstrating is likely sufficient for most contexts (screenshot per John's model):
[cid:image002.png at 01CF51B7.47F83E70]
In any case, if you wanted to go further in detail, I would start the same way, leveraging the wizards to get this far with the roof and to set up everything else pertinent to your study prior to detailed mode edits.

In detailed mode, you could most simply take this a bit further by correcting the two resulting surfaces' area inputs to effect equivalent surface area for the actual barrel shape.   Before taking the effort of splitting this into additional strips (the next logical degree of "exactitude"), which would not be a small degree of effort, I would think well on what effects that would have relative to a 2-surface approximation per above.  As I'm seeing it, the differences are tied up in the barrel vault's "self-shading" nature when the sun is at lower angles, and the magnitude of difference on loads between the above 2-facet approximation and a "higher resolution" barrel with more facets (at least for such a shallow barrel shape) should be small-to-nonexistent, depending largely upon building orientation relative to the annual sun position.

For the purposes of an exacting thermal study, and time allowing, I would concern myself first with the shading effects of surrounding buildings and equipment (noting the adjacent screened rooftop equipment in one of the photos shared) - such elements could easily have a larger thermal impact on the roof's loads, and potentially could make the roof's shape a relatively moot point.

If the purpose of your model isn't to get nitty-gritty into the roof loads, for such a shallow barrel, I wouldn't discount going the other direction and approximating with a single flat roof surface (perhaps adjusting the roof area and space volume in detailed to compensate, as mentioned above).

Hope that helps!

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Saturday, April 05, 2014 4:10 PM
To: Jeff Haberl; Joe Huang
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Difficult roof

Gentlemen:

I sent Katia an example from the eQuest wizard for which I showed her on Screen 3 where the checkbox was for a peaked roof and the way you can change the angle.This is not the Sydney Opera House roof, this can be energy corrected with a 5 or 10 degree tilt roof.

John

From: Jeff Haberl <jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>>
To: Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>>
Cc: "equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>" <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Sent: Saturday, April 5, 2014 12:45 PM
Subject: Re: [Equest-users] Difficult roof

FYI.

I think this is a waste of time for and opaque surface. Perhaps 2 or 3 surfaces will suffice as long as the area = the intended area.

This problem was studied in ASHRAE RP1468 for windows.

Jeff

Jeff S. Haberl, Ph.D., P.E., FASHRAE, FIBPSA
Department of Architecture
Texas A&M University
College Station, Texas 77845-3581
Office: 979-845-6507, Lab: 979-845-6065
Fax: 970-862-2457, jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>, http://www.esl.tamu.edu/

On Apr 5, 2014, at 2:40 PM, "Joe Huang" <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>> wrote:
Katia, John,

I can see the attached two JPGs, so the pictures have been attached.  Looking at them, the roof looks like a very shallow barrel vault.  Since eQUEST  or any other simulation program that I know of, accepts only planar surfaces, you will have to decompose the roof into a number of strips running lengthwise.  Since these strips will be skinny rectangles, they can be input either with WIDTH, HEIGHT, TILT, etc., or as POLYGONs.  John has details on how that's done in eQUEST.

Joe

Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 108D

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>

http://weather.whiteboxtechnologies.com/ for simulation-ready weather data

(o) (925)388-0265

(c) (510)928-2683

"building energy simulations at your fingertips"

On 4/5/2014 8:59 AM, John Aulbach wrote:
Katia:

Are you sure you attached the pictures. I dont see any attachment.  I usually stay away from exotic roofs, unless a tilt is, say, in a major direction.

If you really want to deal with it, you will need to create a polygon in the wall corrdinate system.for each roof section and spatially move them in the right direction using the building coordinate system . This is all in the Detail Edit mode.

Do you understand the different coordinate systems? You can find the explanation in the DOE2.2 Help Menu.

John R. Aulbach, PE

From: katia mailto:katialattouf92 at hotmail.com
To: mailto:equest-users at lists.onebuilding.org mailto:equest-users at lists.onebuilding.org
Sent: Saturday, April 5, 2014 8:31 AM
Subject: [Equest-users] Difficult roof

Dear equest-users,

I am attaching two pictures of a location I am studying.

I am facing difficulties in drawing the roof in eQuest using the pitched roof section.

How can I do it?

 Thank you for help,

KL

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