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[EnergyPlus_Support] Re: Residential Multifamily Infiltration & Ventilation
Hello and thank you for the response. I have played around with changing the height difference and have found, for my model at least, which doesn't have a significant window open area available for natural ventilation, the results are not too sensitive to changes in the height. If using the ZoneVentilation:DesignFlowRate object you have to somehow estimate a design flow rate, which I don't understand how to do when talking about natural ventilation. Do you have any guidance?
Thanks again,
Alea
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Lixing Gu <gu@...> wrote:
>
> 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@...>:
>
> >
> >
> > 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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>
>
>
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