[Equest-users] eQuest Infiltration Modeling as Airflow (CFM/ft2)

[Mark Stout]

I would use ACH and base it on -50 Pa and the standards the AHJ has set.
For example, IECC sets some zones to 3 ACH, but the AHJ may/can/do override
that and may up it to 5 ACH.  Then you just work backwards to arrive at
ACH, e.g.  the formula for CFM is (5 ACH  ÷ 60 Minutes) x Volume = CFM50.
Now you know what your max infiltration.


On Wed, Dec 23, 2020 at 12:50 PM Omer Moltay via Equest-users <
equest-users at lists.onebuilding.org> wrote:

> Dear All,
>
> eQuest allows inputing of infiltration airflow as CFM/ft2 (of indoor space
> in detailed mode) for every zone.
>
> I have calculated CFM/ft2 values for each zone in my model, but this
> calculation has been done for a outside - inside pressure difference of 50
> Pa. Or I can do the calculation for any arbitrary pressure difference.
>
> The question is, since infiltration is very much pressure dependent, what
> pressure difference does eQuest assume when the infiltration airflow input
> is utilized? I know that it will not take into account the dynamic changes
> in pressure dif. during the simulation due to wind effect or other effects,
> but I just want to be able to input a reasonable value since a calculated
> infiltration at 50 Pa is very different from say, at 5 Pa. The answer is of
> course, at whatever pressure difference the zone is anticipated to be
> operating, so what would you recommend for low-rise commercial buildings?
> Or any other guidance would be appreciated.
>
> Or should I convert my calculated values to ACH and use that input, as
> that takes into account wind speed changes? Again, what is the reference
> pressure dif. to use there?
>
> Thank you,
>
> Ömer Moltay, LEED AP BD+C, ASHRAE BEMP, ASHRAE CPMP
> Mimta EcoYapi, LEED Proven Provider
> Hekimsuyu Cad. 559. Sk.
> No:39 34255 Kucukkoy Istanbul Turkey
> Tel: 90-212-617-2296
> Fax: 90-212-617-2297
> Mobile: 90-533-957-1394
> www.eco-yapi.com
> www.buildingenergymodels.com
>
>
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-- 
Kind Regards,
Mark Stout, President
HERS I & II, BPI BA, MFBA, RESNET HERS
Lighting & Mechanical Acceptance Testing
CALGreen Inspector/Plans Examiner

Apollo Energies, Inc.
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