[Bldg-sim] ASHRAE question

Nick Caton ncaton at smithboucher.com
Tue Jun 22 09:16:04 PDT 2010

I can confirm: I learned during and after schooling that the choice to
use any set of columns is the designers' preference.  Some designers
will flip between based on elements of the project at hand, and others
will always stick to one set of columns based on their personal
tolerance/perception of the stringency of each set of conditions.


I don't know if ASHRAE intended this, but personally I always use the
most stringent figures as a rule when sizing up equipment.  My reasoning
is I'm a young designer who hasn't fully grasped where less conservative
criteria are acceptable, and I choose to control the potential for
oversizing via final "rule-of-thumb" / comparative design checks and the
occasional investigative energy model.








25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.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 10:29 AM
To: Seth P. Spangler
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE question


My original response to the question was it was designers preference.
This seems to be not entirely wrong, as it could be clients preference
or space use that has some influence on the designers choice of design
conditions.  Thanks for you input.

On Tue, Jun 22, 2010 at 11:29 AM, Seth P. Spangler <sspangle at rmf.com>



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

Rob Hudson

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20100622/c2ce38bc/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1459 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20100622/c2ce38bc/attachment-0001.jpeg>

More information about the Bldg-sim mailing list