How to Model Infiltration based on Pressure

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As part of the Estidama, the local ABU Dhabi requirements, we are required to model "building air leakage rates" on 2l/s/m? at 75Pa. Is it possible to model this in equest? The help file would suggest so if AIR-CHANGES/HR is used but this is corrected for wind speed.

Are the corrections held in the P-Inf and C-Inf (perimeter and core infiltration?) schedules or are they calculated during the simulation run?

Any help would be gratefully received.



Aristoprat's picture
Joined: 2011-02-16
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Here is a link to a paper published by PNNL discussing some guidelines
for converting building leakage rates at a known pressure to energy
model infiltration inputs.

It is written in the context of EnergyPlus, but eQUEST/DOE-2 includes
the same infiltration model (AIR-CHANGE -> AIR-CHANGES/HR). In my
experience using this guideline, you'll have to do some calculations of
exterior wall area and perimeter zone floor area to come up with the
correct infiltration inputs for each SPACE; keyword defaulting can come
in handy for this task... Also, this guideline doesn't go into depth on
how to develop infiltration schedules that reflect the design capacity
and control of different types of ventilation systems. Rather from what
I gleaned, the guideline is simply 1.0 when fans are off, and 0.25 when
fans are on. Finally, keep in mind that DOE-2 calculates a local wind
speed from weather file wind speed and SITE-PARAMETER inputs that
describe characteristics of both the weather station and the terrain
local to the building. These parameters (which I overlooked until
researching these infiltration models), do have an impact on the
calculation of hourly SPACE loads, since the local wind speed
calculation not impacts the wind-dependent infiltration model, but also
exterior (wall and window) film conductance.

The authors acknowledges that the recommended model addresses only
"wind-driven" infiltration, so if stack-driven flow is a major component
in your building, you may want to figure out a way to adjust your
inputs/schedules to account for this; a combination of AIR-CHANGES/HR
and the other model input, INF-FLOW/AREA, could be one approach for
dealing with this. The DOE-2 Crack model does attempt to account for
stack driven flow, but this model is sensitive to it's many,
component-specific inputs, which are often difficult to characterize.

David Reddy

David Reddy3's picture
Joined: 2011-09-30
Reputation: 0

Hello all,

Am trying to model a small commercial building in Toronto and applying as many passive techniques as I can. While designing shading, I want to apply movable exterior shading (please advice if this will be one of the best techniques or there is a better option). Can anyone share any example with appropriate shading schedules designed. I specific need guidance in designing these schedules. How do we take into consideration the assigned weather file in doing so?

Your response and help will be greatly appreciated.



Shalini Modi's picture
Joined: 2011-09-30
Reputation: 0

Thanks, Ashu. Yes, I modeled overhangs (but not fins). I want to model movable shading, which moves according to the movement of sun specially in the east side to prevent overheating. So I was wondering if designing some schedules will be helpful and if so, how to do that. Would you suggest that overhangs and fins are all I would need (for a heating dominated region) instead of movable shading?


Shalini Modi's picture
Joined: 2011-09-30
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If you are moving your shades to block all direct sunlight - could you zero out your glass shgc? The drawback is that it would block out diffuse sun at times when the shades are not deployed. Do you have daylight dimming of lights? If so you need to captur the loss of visible light as well.

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Sami, Vikram's picture
Joined: 2011-09-30
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If I understand your "movable shading" right as a retractable awning, one technique to consider is setting up a schedule that changes the transparency of the shading overhang so that it is opaque when you want the shade out and transparent when you want the shade retracted. You could model multiple positions of the shade by splitting the shade into multiple sections. For example, if the shade is extended only half way out at times, divide the shade into two halves and make the half closest to the wall opaque while the outer half is transparent.
Keith Swartz, P.E., LEED AP

Keith Swartz's picture
Joined: 2011-09-30
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