Warehouse configuration on Ashrae

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Hi all,

Im a bit confused with the classification of Ashrae 90.1 2007, Im currently
modeling a facility of a total of 47,600 SF including a 28,000 SF
Warehouse. The facility includes 2 levels of offices, breakrooms, etc and a
double height warehouse adjacent to them. The proposed design is composed
of 2 AHUs, one for the first floor, one for the second and a only heating
and ventilation system based on 2 boilers for the warehouse. According to
this, the baseline should be a System 5 Packaged VAV with Reheat, Packaged
rooftop VAV with reheat, Direct expansion cooling type and Hot-water
fossil fuel boiler for heating. One system per floor, but my confusion is
on the part of the warehouse. Should I model an additional Cool and Heat
System for the warehouse even though in the proposed we have it as only
heating and ventilation system? If so, does it have to be the same type of
system specified (System 5) or can it be System 3 or 4 instead?

Thanks.

Karen Smith

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Karen,

You should refer to the updated ventilation/heating systems added by addendum DN to ASHRAE 90.1-2007. These are also included in the 2010 version of 90.1, but the system numbering is different.

The fan power for the ventilation system needs to be separate from the heating fan power (e.g. like a wall mounted prop fan and a separate unit heater). This is now the baseline for 90.1-2007 where no cooling system exists (system is just ventilation and heating). LEED modeling guideline references this updated system type as well. By the way, the fan power for the ventilation is very low so if you have a common system for heating and ventilation then you will likely be significantly over on fan power.

http://www.ashrae.org/File%20Library/docLib/StdsAddenda/90_1_2007_dn_do_dp_dq_dr.pdf

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Scott

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Karen,

Can you follow Addendum dn in this case? (See attached.) This scenario is exactly why the ECB subcommittee drafted dn.

The warehouse area is the "predominant condition" for this building and unfortunately the non-warehouse area is less than 20,000 sqft which would have allowed Exception a of G3.1.1 to come into play. System 5 is the baseline system for the entire baseline building design. You could investigate if Exceptions b or c to G3.1.1 apply.

Is the warehouse heated with a total output capacity greater than or equal to 3.4 Btu/h*ft2? If yes then the warehouse is considered a conditioned space and must be both heated and cooled per section 10 of Table G3.1. (Note that letter d. of section 10 requires the Proposed to also be heated and cooled with a system identical to that of the baseline.) If no then the warehouse is not considered a conditioned space and its baseline system shall match the proposed. That would then also allow the non-warehouse area to fall under baseline system 3.

One last note. Even though you may be required to cool a space in your model that in reality is heated only, your cooling setpoints must be the same between the baseline and proposed but you're only required to have a 5o F dead band between your cooling and heating setpoints. 95o F is definitely 5o F greater than say 70o F. Food for thought... ;)

Scott Hintz
CEM, LEED-AP BD+C, BEMP

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