Sambhav,
There is a range of cfm/sf depending on type of space, etc. A really good
resource for them is a little book that ASHRAE publishes that has all kinds
of "rules of thumb" in it, although I just looked for it in their
publication catalog and didn't see it,
Anyway, it depends of type of space, space usage, whether it is an interior
or exterior space, etc., and seems to hover around 1 cfm/ft. It has always
made me wonder why the eQUEST default is 0.5 cfm/sf, because that number in
almost all cases will be too small. Since we're dealing with Q = 1.08 cfm
delta T a lot in our annual energy calculations this points to a high
probability that the hours of cooling/heating will be outside of their
throttling range. I almost always raise the cfm/sf right away when I start a
model.
Hope this helps,
Carol
?ASHRAE Pocket Guide? is handy, page 166 and 167. Put a sticky note on that
page for sure!
Most of the items in the Pocket Guide can be found somewhere in the
handbooks as well, although I?m not exactly sure where this information
would be.
David
*
*
*David S. Eldridge, Jr.**, P**.**E**.**, LEED AP BD+C, BEMP, HBDP*
*
*
* *
*From:* equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Carol Gardner
*Sent:* Thursday, March 03, 2011 9:54 AM
*To:* sambhav tiwari
*Cc:* eQUEST Users List
*Subject:* Re: [Equest-users] [Bldg-sim] supply air rate
Sambhav,
There is a range of cfm/sf depending on type of space, etc. A really good
resource for them is a little book that ASHRAE publishes that has all kinds
of "rules of thumb" in it, although I just looked for it in their
publication catalog and didn't see it,
Anyway, it depends of type of space, space usage, whether it is an interior
or exterior space, etc., and seems to hover around 1 cfm/ft. It has always
made me wonder why the eQUEST default is 0.5 cfm/sf, because that number in
almost all cases will be too small. Since we're dealing with Q = 1.08 cfm
delta T a lot in our annual energy calculations this points to a high
probability that the hours of cooling/heating will be outside of their
throttling range. I almost always raise the cfm/sf right away when I start a
model.
Hope this helps,
Carol
Sambhav,
I agree with Varkie here. It is best to work with the design engineer and
ask him/her what cfm/sf he/she is using for the space. It is usually
different for exterior and interior spaces.
I would not suggest doing it at the system level, rather at the zone level.
If you are not working with a design engineer, get yourself some resources
and study up. Supply air is provided to offset loads to space, meet comfort
needs of the occupants and to ensure a healthy environment. Hit and/or miss
energy modeling, i.e., making changes to a model to get rid of hours outside
a throttling range is not what you should be doing, and I know, we all do it
sometimes. Far better, however, to try to figure out why those hours are
there and fix them that way.
Finally, thanks for the elevated status but I am a Ms. Carol.
Best,
Carol