Window operation

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Dear all,
Does any of you know if we can model the exterior windows to be opened based on
the zone temperatures?
For example I want to operate the exterior windows and open them if zone
temperature exceeds
23 degrees and outdoor temperature is higher than 15 degrees.
Is it possible?

Thank you in advance.

Best Regards
Sinan Senel

sinan senel's picture
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Joined: 2011-09-30
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Sinan Senel,

Under HVAC systems there is an outside air tab with a natural ventilation
tab. Use it with a schedule attached to temperature and you should be fine.
There is even a textbox that says window probability open.

Thanks,

PETER HILLERMANN

Peter Hillermann2's picture
Joined: 2011-09-30
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Sinan Senel,

Please keep in mind if you are using windows as natural ventilation that
ASHRAE and LEED see this as a different calculation in doing energy modeling
and that you will not be using an HVAC system in that zone and shall be
compared against not using HVAC in that zone. I just ran into this issue
with a project we were doing where I wanted to use the natural ventilation
to my advantage and found out I could not.

Thanks,

PETER HILLERMANN

Peter Hillermann2's picture
Joined: 2011-09-30
Reputation: 0

Yes, in addition to that you need to model/specify your building windows as
"operable". If they are specified as a "fixed" window then the simulation
will not "open" them to the outside air conditions and subsequent wind speed
from the weather file.

Always when trying to simulate some amount of NV you must have specified
operable windows & window area separate from your fixed windows and window
area AND you will have a temp schedule so that the program knows how you
want it to react. Also remember that these attempts to represent energy
savings from operable windows or NV strategies are only static calculations,
therefore there are no iterations to take advantage of the dynamic
principals of NV in DOE-2. AND this is not a good way to analyze thermal
comfort of the occupants with NV design strategies. The only purpose for
applying this approach in DOE-2 is to minimally represent potential energy
savings (mostly fan energy) in your whole building analysis.

Better tools (and typically more expensive tools) are available to properly
analyze the dynamic characteristics of Natural Ventilation strategies &
occupant thermal comfort, especially if you are trying to do this in
support/compliance for the LEED credit. One tool is TAS (thermal analysis
software), and maybe TRNSYS (I'm not exactly sure of it's capability), and
of course CFD.

pkg

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Dear Peter and Pasha,
Thank you for the quick and the useful response.
Actually, I want to see the effect of natural ventilation on overheating hours.

And the only that I can calculate overheating hours is to check whether zone
temperatures are over a certain limit by using hourly reports.
Do you think it would be ok to use NV for this purpose?
And do I get it right that energy savings in fan energy consumption is due to
the ourside air supllied to the zone by NV?
Thanks

Best Regards
Sinan Senel

sinan senel's picture
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Joined: 2011-09-30
Reputation: 0

Yes, the fan energy savings is achieved by the system fans being turned off
when you tell the program that NV strategies are 'turned on'. and yes, you
are on the right track with the use of the hourly reports too.

pkg

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600