Non conditioned regularly occupied space

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Just to clarify - does the remaining 95,000 ft2 of regularly occupied office have an engineered natural ventilation scheme?

There are some cases where 90.1 asks for cooling systems to be modeled even if none are proposed. You'll need to find out if those conditions apply to you.

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David Eldridge's picture
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Joined: 2012-05-08
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Dear David,

The 95,000 ft2 area has only normal ceiling fans.

As I read in ASHRAE 90.1, it says, we shall model HVAC (Cooling or Heating)
even if there is NO system proposed. But in this case, VRV system is
proposed for 5000 ft2 area, so how shall I proceed with the remaining
95,000 ft2 area?

Thanks,
Vamshi.

vamshi ranga's picture
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Joined: 2012-11-12
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Dear All,

We are modeling Non residential building for USGBC New Construction rating,
which has regularly occupied (office) area of 100000 sq ft, out of which
only 5000 sq ft of the regularly occupied (office) area is conditioned with
VRV systems.

Could you please let us know how the conditioned area shall be considered
in Baseline and Proposed case. my doubts is,

Shall this be modeled with 5000 sq ft conditioned area in both Base and
Proposed or Is there any minimum requirement for percentage conditioned
area?

Thanks,
Vamshi.

vamshi ranga's picture
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Joined: 2012-11-12
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Hi guys.

I somehow agree with Arvind. However, ASHRAE system type selection is based
on conditioned area and not overall area.

If you think you need to claim savings for natural ventilation, the same
can be done using exceptional calculation. One approach I saw and was
approved by GBCI was when a HVAC system was modeled in both Baseline and
Proposed Case. The schedule of Proposed Case was so adjusted, to turn the
system off when the adaptive comfort temperature is met in the space in the
Proposed Case. That ways, the Baseline system was still running to meet
space temperatures while the Proposed system was not running and hence the
savings.

There are few CIRs on this which I might be able to share in the due
course.

Thanks

Kushagra

Kushagra Juneja's picture
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Joined: 2013-02-21
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HI Vamshi,

If the 95,000 sqft spaces are deemed to be conditioned per Section 3 ASHRAE
90.1 space definition, your Baseline system type based on 100,000 sqft not
5000 sqft. You will then have to model a baseline cooling and heating
system in the Proposed model and model your office space system as
designed. You can then claim savings for natural ventilation / fans using
exceptional calculation method.

Hope this helps.

Regards
Ramya

r s's picture
r s
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Joined: 2013-07-02
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Hi Vamshi,

Based on your sqft and fuel size you will have system type and that will be system 6 in your case. Baseline model and proposed both will need heating and cooling system for non-conditioned space. But you can set up high cooling set point for baseline and proposed model to avoid any cooling in the non-conditioned space.

Thanks,
Arvind

Singh, Arvind's picture
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Joined: 2013-08-31
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I am telling you with my experience. The minute you include this space in your model your system type will change. You have to assigned a system to "95,000 ft2 of regularly occupied office" and claim the saving of natural ventilation using exceptional calculation.

Arvind

Singh, Arvind's picture
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Joined: 2013-08-31
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