[Bldg-sim] Really need some deep DOE-2 theology on this one..

Maria Karpman maria.karpman at karpmanconsulting.net
Sun Sep 29 08:01:38 PDT 2013


John,

 

Having extra exterior roof area is a fairly common mistake in eQUEST models
involving multiple shells. It typically originates on DD Wizard Screen 3,
when roof construction is specified in the Construction list box for a shell
that has no roof (i.e. shell that includes only the middle floors of the
building), instead of setting it to "-no exterior exposure (adiabatic)".
Any exterior surface in eQUEST will conduct heat between the parent space
and the ambient, even if it is adjacent to another conditioned space based
on 3D view, so having extra roof area does affect simulation results. The
easiest way to fix the problem is to delete the extra exterior roof
surfaces. Converting them to interior walls as Patrick suggested is a more
precise approach, but is also more time consuming and will have negligible
impact on results for most projects, especially if the result of interest is
Appendix G performance rating. 

 

Thanks,

 

Maria  

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Patrick J.
O'Leary, Jr.
Sent: Saturday, September 28, 2013 9:41 PM
To: John Aulbach
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Really need some deep DOE-2 theology on this one..

 

this sounds like you have multiple shells in one model for this to occur?
i'm pretty sure equest views an exterior wall/roof as an exterior wall/roof
even if it is bounded by an interior wall.  i had this problem come up on
one of my own models where i ended up having a building wing meet the
building trunk & as i had put them in as 2 separate shells equest did not
recognize the dividing wall where the wing met the trunk as being an
interior wall & assigned it (via the wizard) an exterior wall definition.  i
didn't catch this until reviewing the unmet load hour ss-r & s-va reports &
couldn't figure out why the load was so high.  changed the definition of the
wall to interior (with a door) in detailed mode and the unmet load hours
went to zero and the load came down.

my understanding (in my case) is that if you create multiple shells and
place them with a common wall that you want to be an interior the shell
rotations need to be zero, even if you have the separation between the two
shells occur at a 45 deg angle (then ask mr. architect about that one).   

On 9/28/13 4:47 PM, John Aulbach wrote: 

Hi Gang:

 

I need to elite for this one, and you know who you are..

 

I am reviewing another party's eQuest model submitted for LEED. The reviewer
noted that the roof area far exceeded the actual building footprint.

 

Well, guess why? Somehow, the other party made several floors ROOFS instead
of ceilings. I might be able to simply turn the exterior spaces into
interior ceilings, but one roof (over an unheated underground garage) is
partially uder the building and partially exposed to the "sidewalk/entrance"
of the building.

 

The BIG Kahuena is this..if a space is crammed next to an adjacent space and
one of the spaces claims an Exterioir surface between them, does DOE-2 think
that Exterior surface is seeing outdoor conditions? Or does it ignore such a
thin and merely considers the heat transfer between the spaces (like the
wall/roof is NOT exposed to the outdoors)?

 

My approach is this (unless you disagree)..leave the Exterior wall/roof
along and explain that the model (now in Detailed Edit form) would need
major surgery to correct to show actual roof area. Having the "roofs" there
versus floors will not change the thermodynamics of heat transfer.

 

I yield to the floor.

 

John Aulbach, PE

 

 

 

 

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