The infiltration from roof and walls should be kept separate for several
reasons. First the reliable modeling of UFAD is on the immediate horizon
and the stratification necessary to make UFAD successful brings relatively
warmer air into close contact with the infiltration surface -- roof. The zenith
pointing surface normal from a hot surface also has a much higher convection
coefficient. Energy Plus does not currently model stack effect directly but
combining the wall and roof infiltration area largely closes the door on incorporating this
capability in the future.
Time of Day modeling of infiltration may become significant in some climates. Any
bow hunter will tell you that there is a marked reduction in light breezes at sunup and
sundown.
Cinder block basement walls are problematic vis a vis infiltration because of several
different methods used to seal the top course. Some bricklayers use a solid 4x8x16
block laid down flat especially if the wall is 8 inches thick. Others use block rubble
to fill the cores with a splat of mortar. Still others may not effectively seal the cores at
all. I have a 1986 custom designed / partial DIY built solar house. The air infiltration
from the top of the block walls varies 8 to 1 depending on orientation and top course
type. The walls themselves show only a 3 to 1 variation, but no sealer products were
used on the wall surfaces.
John Ross
krgowri wrote:
__._,_.___Linda - Thanks for the quick response. Based on the recent
sensitivity analysis we have done with DOE2 linear wind speed
coefficients, I would suggest the flow rate per exterior area be
represented as flow rate per exterior wall area. For anyone
interested in providing a total exterior surface area, they could
always use the flow rate per zone floor area option.
- krishnan
--- In EnergyPlus_Support@yahoogroups. , Linda Lawrie <linda@...>com
wrote:
>
> It includes surface areas for the roof and floors - if they are
> exposed to "external environment" or "othersideconditionsmodel" --
if
> they are in ground contact, it would not be included. Right now,
by
> oversight, it may also add in door area (so the doors would be
> represented twice) -- but I'll check on that and issue a change
request if so.
>
> It also looks like the "exterior surface area" is not printed out
on
> any report -- I will rectify that if it is not (and it doesn't
appear
> to be - exterior gross and net wall area appear to be printed but
not
> exterior surface).
>
> Do you see it as a big detriment that it might include roofs? Or
> floors that would be exposed to external environment?
>
> Linda
>
>
> At 02:11 PM 6/4/2008, krgowri wrote:
>
> >I am trying to use the new 'Flow per Exterior Surface Area' option
to
> >specify infiltration. Can any one confirm if this surface area
> >includes roof, floor, basement wall areas in scaling the flow rate
per
> >unit area input for the zone?
> >
> >Generally the infiltration rates are specified as flow rate per
> >exterior wall area and would like to know if this needs to be
converted
> >for EnergyPlus input.
> >
> >
> >-------------------- --------- -------
> >
> >The primary EnergyPlus web site is found at:
> >http://www.energyplus.gov
> >
> >The group web site is:
> >http://groups.yahoo.com/ group/EnergyPlus _Support/
> >
> >Attachments are not allowed -- please post any files to the
> >appropriate folder in the Files area of the Support Web Site.
> >
> >EnergyPlus Documentation is searchable. Open EPlusMainMenu.
> >under the Documentation link and press the "search" button.
> >Yahoo! Groups Links
> >
> >
> >
>
> [Non-text portions of this message have been removed]
>
The primary EnergyPlus web site is found at:
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Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
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