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Re: [EnergyPlus_Support] Re: Residential Multifamily Infiltration & Ventilation
Alea:
It is not easy to figure out the values of "height difference". This
object is mainly for people to use if the height difference could be
esitmated. A half of buildign heaight is a good guess. If you can not
determine the value, it is better to use the
ZoneVentilation:DesignFlowRate object.
Hope this helps.
Lixing
Quoting adcamtor <adcamtor@xxxxxxxxx>:
>
>
> Hi Alea,
>
> I am at the same stage, I have calculated the ventilation with the
> WindandStackOpenArea objects and the results seem to be accetable.
> But, I am not sure if I have done it correctly estimating the
> "height difference", I have used one half height of each opening
> area, in my case, small ventilation openings (no doors, no windows).
>
> Regarding the "height difference", I have read in the ASHRAE
> fundamentals the next paragraph:
>
> Estimation of "height difference to neutral pressure level" is
> difficult for naturally ventilated buildings. If one window or door
> represents a large fraction (approximately 90%) of the total opening
> area in the envelope, then the NPL is at the mid-height of that
> aperture, and height difference to NPL equals one-half the height
> of the aperture. For this condition, flow through the opening is
> bidirectional (i.e., air from the warmer side flows through the top
> of the opening, and air from the colder side flows through the
> bottom).
>
> I cannot help you too much, I hope someone more expert helps us.
>
> Adrian.
>
>
>
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "aleagerman22"
> <agerman@...> wrote:
>>
>> Hello,
>> I am new to Energy+ and am modeling two new construction
>> multi-family buildings. One is 3 stories with exterior entrances
>> and the other is 10 stories with interior hallways. I am struglling
>> with how best to model natural ventilation and infiltration, both
>> due to exhaust fan operation and envelope leakage based on a
>> measured/expected SLA. My zoning is fairly simple with a single
>> zone per apartment unit. This is new construction so the assumption
>> is that envelope sealing is decent and there is not significant
>> connection between the individual units.
>>
>> The AirflowNetwork module appears to be a very powerful tool but
>> perhaps too complex for what I'm trying to do. Also, there are many
>> modeling inputs, like Wind Pressure Coefficients, that I don't have
>> and would have to use defaults or those measured by others which
>> may reduce accuracy. Thoughts? The other alternative appears to be
>> through ZoneVentilation & ZoneInfiltration. However, if I enter my
>> exhaust fans and envelope leakage separately, total infiltration
>> will be a summation of the natural infiltration and mechanical
>> ventilation and will be overestimated according to ASHRAE.
>> Regarding natural ventilation the
>> ZoneVentilation:WindandStackOpenArea appears to be a good option;
>> however, the E+ documentation advises against it because the
>> "height difference" is particularly difficult to estimate. Is the
>> ZoneVentilation:DesignFlowRate to the best way to go?
>>
>> I would greatly appreciate any advice or guidance from anyone who
>> has experience with this. Thank you in advance.
>>
>> Alea
>>
>
>
>
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