[Equest-users] Mixed construction roof

[Bishop, Bill]

Lars,
 
See this earlier post:
 
http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2008-Mar
ch/007123.html
 
Partial roofs are difficult to work with, especially if a single plenum
is modeled at the top of the entire floor. If the 2nd floor has no
plenum, or has a separate plenum above each space, then you can
add/modify individual roof surfaces to each space. Add roofs (exterior
surfaces), specifying "top" location. Start by making a copy of the
space polygon, then modify the coordinates to match the shape and
location of the roof. This can be time consuming and trial-and-error
until you get the hang of it. As the earlier post mentioned, if the 3-D
view is unimportant, you can just create a square roof with the correct
area and put it anywhere, and assign it to the space (although I would
think shading should be considered). Create and assign as many roof
constructions as you feel are appropriate. You could try making two roof
constructions to start with, using the extremes of R value, and
assigning the same construction to all roofs to see how much of a
difference it makes to the model.
 
Regards,
Bill
 
William Bishop, EIT, LEED(r) AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
bbishop at pathfinderengineers.com
www.pathfinderengineers.com
P Please strive to live sustainably.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Lars
Fetzek
Sent: Thursday, July 16, 2009 9:36 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Mixed construction roof
 
Hello,
 
    The building that I am modeling consists of three floors.  Because
the 3rd floor significantly differs from the 1st and 2nd floors in its
shape and size, I have modeled the 1st and 2nd floors as one shell
(discussed in my previous e-mail, titled "Disappearing components") and
the 3rd floor as a separate shell and project altogether.
    The present e-mail concerns the modeling of the 2nd floor roof.  The
portion of the modeled roof directly beneath the 3rd floor should be
adiabatic.  The remainder of the 2nd floor roof is constructed in
various ways with insulation of varying thickness and covered in some
places by deck, in other places by grass, in other places by nothing
special, and in some places by mechanical equipment.  Were this a simple
shell, I would be inclined to enter a single set of heat-transfer
properties of the roof that results from a manually calculated average
of values weighted by area.  However, the 2nd floor includes several
rooms and HVAC zones, each of which is under a specific portion of the
actual 2nd floor roof and/or under the 3rd floor.  Therefore, the
simplification that I described above seems a bit dicey.  Does anyone
know of a way to properly model (in eQuest) a roof comprised of such
multiple constructions?
    Thank you in advance for any advice.
 
Lars Fetzek, EI
Phoenix Engineering Group
Tampa, Florida
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