[Equest-users] Infiltration issues whith more than one shell
Joe Huang
yjhuang at whiteboxtechnologies.com
Fri Mar 2 12:39:53 PST 2018
The point I'm trying to make is that DOE-2 and presumably eQUEST derives the infiltration
rate from user input of the EFFECTIVE-LEAKAGE-FRACTION for the SPACE that is expressed in
CFM/ft2 of floor area. This infiltration rate is not affected by the amount of exterior
walls in the spaces or their proximity to each other. In your examples, aren't the
infiltration rates for the building just the sum of the infiltration rates for the zones
(presumably perimeter and core) adjusted by their floor area ?
Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
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 3/2/2018 7:33 AM, Daric Adair wrote:
>
> All;
>
> Confused as to how Bruce’s answer isn’t directly applicable. What he detailed in the
> first instance is directly in line with my experiences. eQuest wizard modes doesn’t
> realize that two abutting/touching shells should have interior walls. If a space wall
> touches a shell wall, an exterior wall is created.
>
> -If a zone boarders a shell, eQuest creates an exterior wall.
>
> -If a zone does not touch a shell edge, eQuest makes an adiabatic interior wall.
>
> -If two shells are touching and each have zones touching the common wall, two exterior
> walls are created; one in each zone. Wizard eQuest doesn’t distinguish if two shells are
> 0 feet apart/touching or if they are 25 feet apart. (example described below)
>
> If eQuest uses exterior wall area to calculate a floor area normalized infiltration
> rate, and there are ‘extra’ exterior walls which are actually interior walls where
> shells touch, then the infiltration rate will be calculated as though the two shells
> were never touching. This will increase the calculated infiltration rate since these are
> not actually interior walls.
>
> Bruce’s solution only neglected to mention that the infiltration rate will either need
> to be corrected for this condition, or ignored/neglected. The second option is not to
> say infiltration is not important – it is important – but requires modeler judgement and
> some math. The length/area of the touching walls is also a factor to consider. If
> project is a large industrial setting as described in thread, yes, probably should
> check/revise. If a small connecting corridor, probably minor and can be ignored.
>
> Did a quick (very simplified ) example. All examples have: 10ft high. No plenum. Set
> Perimeter infiltration to 0.05 CFM/sf. 0.0 core infiltration.
>
> - Made two shells, 50ft x 50ft each. 2 spaces per shell, spliting shell equally. Placed
> the shells touching. The calculated infiltration is 0.0400 cfm/ft
>
> - Made two shells, 50ft x 50ft each. 2 spaces per shell, spliting shell equally. Placed
> the shells 50 feet apart. The calculated infiltration is 0.0400 cfm/ft
>
> - Made one shell, 100ft x 50ft each. 4 spaces per shell, spliting vertically,such that
> the zones are the same area/dimensions as the previous examples. The calculated
> infiltration is 0.0400 cfm/ft in the end cap spaces, and 0.0200 CFM/sf in the middle
> spaces. This is due to less exterior wall area (as expected).
>
> - Made two shells, 50ft x 50ft each. 2 spaces per shell, same spaces as above. But –
> offset the edge of the shells when drawing in wizard mode such that the edge of the
> spaces were not the edge of the shell(s) (refer to image). Placed the shells such that
> the two zones were touching. The calculated infiltration is 0.0400 cfm/ft in the end cap
> spaces, and 0.0200 CFM/sf in the middle spaces; matching as if done in a single shell.
>
> The last example allows the user to change the wall from adiabatic to a heat transfer
> surface easily. Can also modify the infiltration rate as needed & detailed ablve. PNNL
> has published several reports on infilatration rates which can be references as well for
> good information.
>
> Let me (and all of us) know if this seems at odd with previous experiences or overlooked
> a detail. Thanks in advance.
>
> Thanks,
>
> *DARIC R ADAIR*PE, CEM, BEMP
> Mechanical Engineer, Energy Analyst
>
> *Henderson Engineers*
> *Tel* (913) 742-5530
> daric.adair at hendersonengineers.com <mailto:daric.adair at hendersonengineers.com>
>
> *Licensed in*KS
>
> *From:*Bruce Easterbrook [mailto:bruce5 at bellnet.ca]
> *Sent:* Thursday, March 1, 2018 11:19 PM
> *To:* Joe Huang <yjhuang at whiteboxtechnologies.com>; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Infiltration issues whith more than one shell
>
> Thank's Joe, I didn't realize that. There are many quirks with DOE2 and eQuest. I
> haven't looked at that part of the fine print recently. Leakage does depend on the wall
> area and not the floor area in real terms. Buildings have many different wall heights,
> plenums or not, ducted or not, etc. I would guess after normalization that one would
> have to be careful with how manipulations in geometry are done to achieve other effects
> in the model. Infiltration can have a serious effect on a model.
> I can remember a past model where I used this technique for an actual butting of 2
> industrial spaces/buildings. The one area was a cable casing thermal setting zone, 1/2
> height of the warehouse/machinery high bay zone that was adjacent to it. I was more
> concerned with the door and seal between the 2 buildings. I possibly missed the
> infiltration difference seeing it was based on floor area and not wall area. I will
> have to re-read the fine print.
> Bruce
>
> On 3/1/2018 10:32 PM, Joe Huang via Equest-users wrote:
>
> I don't think Bruce's comment is germaine to the problem posed by Menush, since
> Menush is asking about infiltration and not heat transfer through interior walls.
> As far as I know from DOE-2 (always have to add that caveat because I don't work
> much in eQUEST), infiltration rates are normalized per floor area, rather than
> external wall area, mainly because that's how the infiltration models have been
> developed, i.e., effective leakage areas have always been defined as per floor
> area. If you don't think that's right, you can always adjust the input values by
> the ratio of the external wall area to the floor area, as you've described, but then
> you're on your own in coming up with the correlation,
>
> Joe
>
> Joe Huang
>
> White Box Technologies, Inc.
>
> 346 Rheem Blvd., Suite 205A
>
> 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 3/1/2018 6:44 PM, Bruce Easterbrook via Equest-users wrote:
>
> Hi Menush,
> I don't think you have the same thing. eQuest will treat 2 shells butted to
> each other differently than a single interior wall separating 2 zones in a
> shell. It treats the 2 butted walls as exterior walls with a tiny space
> between. They are the same wall in your thinking but they are not. You can
> delete one of them and make the remaining wall an interior wall and assign the
> proper butting spaces on each side of the wall as sharing the wall and
> transferring heating and cooling through the wall. Or you can add an interior
> wall to the original space and separate it into 2 zones. As you have noticed
> there is a difference in the way eQuest treats your 2 solutions. It is
> particular. Now you need to pick the configuration that matches what you are
> trying to model in such a way that eQuest does/treats the wall in the way you
> want it to work.
> Bruce Easterbrook P.Eng.
> Abode Engineering
>
> On 3/1/2018 5:23 PM, Menush Akbari via Equest-users wrote:
>
> Hi all,
>
> I’m having an issue with infiltration and wondering if anyone else has
> noticed this. When I’m in wizard mode, I build a very simple rectangular
> shell and I change the infiltration rate for perimeter zones to 0.05cfm/ft2.
> I leave the core zone infiltration rate to the eQuest default value
> (0.001cfm/ft2). From my understanding, the perimeter zone entered value in
> wizard mode is based on exterior gross wall area. When I move on to detail
> mode, eQuest changes the value to an infiltration value per floor area
> instead of exterior wall area. The values so far make sense and I can do the
> math and get the same numbers eQuest calculates in detail mode. No problems
> here.
>
> The problem however happens when I create different shells. For example,
> let’s say I have the same rectangular building as mentioned above, but I
> split this up into two different shells next to each other (two square
> shells), therefore one of the walls of each square shell is an interior
> wall, which means I should not see an infiltration of 0.05 cfm/ft2 of the
> gross wall area. However when I finish building these two shells in detail
> mode (which would be identical to one rectangular shell), the infiltration
> value is not accurate anymore. Instead of the same numbers as my first model
> (one rectangular shell), the second model calculates an exterior wall
> infiltration value for the interior walls that are budded up against each other.
>
> Has anyone come across this? Is this a quirk with eQuest and just needs to
> be changed manually in detail mode, or am I doing something wrong here?
>
> Thanks for the help.
>
> Cheers,
>
> *Menush Akbari*
>
> BEng, PEng, BEMP, CMVP
>
> Senior Energy Engineer
>
> Mission Green Buildings
>
> /(Mission Green Buildings is the trading name of Mission Green Limited)/
>
> t. 250 777 3380
>
> makbari at missiongreenbuildings.com <mailto:makbari at missiongreenbuildings.com>
>
> _http://missiongreenbuildings.com <http://missiongreenbuildings.com/>_
>
> MGB 5 Years 2
>
>
>
>
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