[BLDG-SIM] Baseline HVAC Type

[gail]

Hi Bill,

I'm of the opinion that many laboratory spaces DO meet the intent of this
exception and MAY be modeled with PSZ systems.  The basis for my opinion is
the 90.1-2004 User's Manual, Section 6.5.2.1, which specifically mentions
"areas of hospitals, operating rooms, and laboratories that must be
maintained @ positive or negative pressures to prevent contaminants from
entering" as examples of zones where special pressurization relationships,
cross-contamination requirements, or code-required minimum circulation rates
are such that variable air volume systems are impractical.  Also, laboratory
spaces often have high process loads meeting or exceeding the 10 Btuh/sqft
threshold when compared against adjacent hallways, offices, and/or
classrooms.

If I were preparing LEED Documentation for a V2.2 lab building, I would
probably provide an accompanying narrative that specifically references the
Appendix G exception, and the User's guide Section 6.5.2.1 clarification.

Best Regards,
Gail Stranske
CTG Energetics


On 5/15/07, Bill Talbert <btalbert at aeieng.com> wrote:
>
>  Can anyone provide feedback on the intent of ASHRAE 90.1 Appendix G
> Exceptions to G3.1.1 which allow changes to the baseline HVAC systems
> prescribed in Tables G3.1.1A and G3.1.1B for spaces with special
> pressurization requirements or spaces where peak thermal loads differ by
> more than 10 Btu/h-sqft? This exception would appear to allow Packaged
> Single Zone air conditioners with gas-fired heating as baseline systems in
> laboratory spaces with high equipment loads and/or pressurization
> requirements. In a large lab building where the baseline system per Table
> G3.1.1A is a VAV system, this could make a big difference in calculated
> energy savings. A recent CIR (February  '07) on the USGBC site implies that
> the exception should not be used although the question involves reheat
> issues as well. It seems that a PSZ system could be modeled successfully to
> meet zone conditions without reheat but does this approach (simulating the
> baseline for a large laboratory building with multiple PSZ systems) meet the
> intent of the exception?  Has anyone else had any experience with this or
> can the A90.1 and LEED folks offer some perspective?
> Thanks,
>
>
>
>
>
>
> Bill Talbert, PE, LEED(r) AP
> Mechanical Systems
> Phone: (608) 441-6677
> E-mail: btalbert at aeieng.com
>
> Affiliated Engineers Inc.
> 5802 Research Park Blvd.
> Madison, WI. 53719
> Tel. (608) 238-2616
> Fax. (608) 238-2614
>


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