External Adiabatic

11 posts / 0 new
Last post

I can't find this thread I remember seeing about turning an exterior
surface adiabatic where new construction meets existing building, ideas?

Arpan Bakshi, LEED AP BD+C

NYCCTgreen's picture
Offline
Joined: 2011-09-30
Reputation: 0

See below. Nick gives a good explanation when I posed the same question
a couple weeks ago.

Chris Swanson, EI

Chris Swanson's picture
Offline
Joined: 2011-09-30
Reputation: 0

Following on, I realized, reading this, that this may be appropriate for my model, where one "exterior" wall is shared with an adjacent warehouse. I'm now working in detailed entry mode now - how can I now make this setting change for this wall without going back into wizards?

Thanks!

MARK DARRALL, AIA, LEED AP BD+C, NCARB

Mark Darrall's picture
Offline
Joined: 2011-09-30
Reputation: 0

Yes, the problem here is I am deep into detailed mode. Looks like we
have to crack open the text edit again.

Thanks
Arpan

NYCCTgreen's picture
Offline
Joined: 2011-09-30
Reputation: 0

I think the u value can be changed to 0.001 to male the wall with almost zero heat transfer when in detailed mode. I tried doing that n it worked.

DEEPIKA KHOWAL

Dkhowal's picture
Offline
Joined: 2011-09-30
Reputation: 0

Arpan, Mark and others:

In detailed mode, there are many approaches that vary from fast to quick, with slightly different end-results. Deepika?s suggestion of forcing low u-value is very clever and something I?ll add to my toolbox!

The absolute simplest/easiest way to eliminate heat transfer across a surface in detailed mode is to delete it. Just let there be a ?hole? in your 3D building =)! The only thing you?re losing with that approach (besides aesthetics?) is that an adiabatic surface has mass which will retain heat, whereas a deleted surface has no mass? here?s a quick summary of the various surface/partition types for reference, copied from an earlier post:

- Deleted/No surface - No heat transfer, no mass [Total disconnect]

- Adiabatic ? No heat transfer, Yes mass

- Standard ? Yes heat transfer, Yes mass (frame/mass partitions)

- Air ? Yes heat transfer, No mass

- Internal ? No heat transfer, Yes mass (another means of specifying thermal mass in a space ? I haven?t used this myself)

If you really want an adiabatic surface (with mass), then you can make an adiabatic surface from an external surface following the pictorial guide I wrote up a while back (attached). This will achieve the same thing the wizards do automatically, with additional flexibilities.

You both may be on top of this, but it bears repeating every so often for everyone?s benefit: This and similar guides/discussions are currently available in the mailing list archives. Every user of eQuest should have the following bookmarked/favorite in their browser of choice!

http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/

http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/

~Nick

NICK CATON, E.I.T.

Nick-Caton's picture
Offline
Joined: 2011-09-30
Reputation: 805

Looks like what eQUEST is doing is turning exterior walls into adiabatic
interior walls. Because even in detailed mode, only interior walls have this
option. This is what the wizard mode exterior wall defined as adiabatic
looks like behind the curtain

"EL1 East Wall (G.E2.I6)" = INTERIOR-WALL
CONSTRUCTION = "EL1 EWall Construction"
INT-WALL-TYPE = ADIABATIC
X = 0
Y = 0
Z = 0
HEIGHT = 9
WIDTH = 158.1
AZIMUTH = 180
..

NYCCTgreen's picture
Offline
Joined: 2011-09-30
Reputation: 0

This is for an EPACT submission.

Subject building has two roof mounted DX units with VAV supply/return.? DX
provided by Turbocor compressors. Terminal units are fan powered VAV (which?I
don't think you can model in eQuest).

But the single line diagram shows a hot water heating coil connected to a 3
million BTU boiler. The coil is DOWNSTREAM from the cooling coil, and you have
yet to reach the terminal reheat units.

This is a glass 10 story building in North Hollywood, CA, so it won't get very
cold there?

DILEMMA..WHAT is the purpose of the hot water coil and how and when will it
operate?

John R. Aulbach, PE, CEM

John Aulbach's picture
Offline
Joined: 2011-09-30
Reputation: 1

I like that. It?s elegant. eQ still wanted Constructions and Layers, so I set the overall U to 0.001 and used an interior wall construction.

Thanks!

MARK DARRALL, AIA, LEED AP BD+C, NCARB

Mark Darrall's picture
Offline
Joined: 2011-09-30
Reputation: 0

I know of a work-around to make an exterior surface (wall/flr/roof) into an adiabatic surface if you already have an adiabatic surface somewhere in your model.

These instructions are for detailed mode and I will try to explain them as clearly as I can.

So let?s say you have an existing adiabatic/interior surface in your model, we will call this surface INTERIOR-1 for reference.
Let?s name the current exterior surface that you would like to make adiabatic/interior surface EXTERIOR-1 for reference.

First start by selecting surface EXTERIOR-1 in the project tree under ?building shell?. Right click this surface and select properties. On scrap paper, copy the parent space as well as all of the information under location & geometry (loc/poly/x/y/z/Azimuth/area/height/width/tilt/ etc..). This will allow you to recreate the surface you wish to change in exactly the same shape and location. Exit out of EXTERIOR-1 properties.

Next, click on the existing adiabatic/interior surface named INTERIOR-1 and select ?create another interior wall?. Name the new interior wall name something close to the name for exterior-1 or the surface you wish to replace. Select the parent space that you copied down for EXTERIOR-1. For create option, select copy an existing component and select INTERIOR-1 from the dropdown. Click ok. A new interior surface properties box should come up and you should see ?adiabatic? selected under surface type. In this new box, copy all of the location and geometry information that you took down for EXTERIOR-1. Sometimes the correct info will already be there and sometimes you will have to input the values you copied down (depending on if it?s a space polygon or not?). Click OK.

TADAA! You should now have an adiabatic interior surface in exactly the same place as the exterior surface you were trying to change. Once you are sure the surface is correct, delete the original EXTERIOR-1 as you will have two identical surfaces on top of each other.

I hope this helps, I have used this method to make adiabatic interior surfaces for models with multiple shells as well as models that are adjacent to existing buildings.

Lyle Keck

Lyle Keck's picture
Offline
Joined: 2011-09-30
Reputation: 1

As you know, App-G does not provide guidance for if/how neighboring
buildings are modeled as long as the decision is consistent in both baseline
and proposed cases. Would be curious to hear about the approach others take
to this, e.g. model both with and without and then choose the most
beneficial option, as far as PRM.

NYCCTgreen's picture
Offline
Joined: 2011-09-30
Reputation: 0