[Bldg-sim] ASHRAE question

Seth P. Spangler sspangle at rmf.com
Tue Jun 22 08:29:07 PDT 2010



I have never read specific conditions of when to use one over the other
however typically the conditions used are dictated by the type of
building. In my experience buildings with low tolerances for temperature
change use the 99.6%/0.4%. These buildings would include hospitals,
laboratories, R&D etc. Buildings with a high level of tolerance will use
99%/1%. These buildings are typically office buildings, higher
education, retail etc.


In the past six months I have seen a huge change in design conditions.
The latest owner has specified design conditions of ASHRAE 99%/1% with
Summer indoor of 78 deg F/50%RH and Winter indoor of 68 deg F. However,
they want the thermostat set point to be 73 deg F year round.


Seth Spangler, LEED(r) AP 


RMF Engineering, Inc 

Ph: (843) 971-9639 ext:1497

Fax: (843) 971-9641 

sspangle at rmf.com


From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Rob Hudson
Sent: Tuesday, June 22, 2010 11:15 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] ASHRAE question


I was asked what influences an engineers decision over design
conditions, and after looking for some textural support in the books, i
could not find anything to give guidance over when to use 0.4/1/2 or
99/99.6 % design conditions.  Does anyone know if this text exists in
the ASHRAE books and if so which chapter?  I also looked into ASHRAE
90.1, but that only addresses efficiencies of equipment and not the
design conditions/capacity calculations.

Thanks in advance,

Rob Hudson

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