[Bldg-sim] OT fresh air

Jim Dirkes jim at buildingperformanceteam.com
Tue Mar 5 10:03:48 PST 2013


Dear Chris,
My understanding of the area ventilation requirement is concern for off-gassing of VOCs and similar chemicals which are deemed harmful.  It will be difficult to  avoid that requirement!
On the other hand, my experience with many warehouses and distribution centers is that it is very rare to have less than about 0.2 air changes per hour (average) from infiltration. For a 30 foot tall warehouse, that is equivalent to about 0.1 cfm / sq.ft.
The summary, assuming I did the math properly in a hurry, is that you’ll heat the 0.06 cfm/sq.ft. plus some more just for infiltration – so nothing is “wasted”.  Do you feel any better ☺?
p.s., Almost all of my warehouse experience is with heated-only facilities.  Perhaps the air conditioned facilities are better constructed, but I’m doubtful.

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris Jones
Sent: Tuesday, March 05, 2013 12:24 PM
To: David Eldridge; bldg-sim
Subject: Re: [Bldg-sim] OT fresh air

This is a timely subject.  I have been working on some very large distribution warehouses.  The staff are never all in one place at one time except morning, breaks and the end off shift.  The local authorities are asking that ASHRAE 62.1 be followed - warehouses at 0.06 cfm/sf.  A half million square foot warehouse ends up with a lot of out door air that needs to be conditioned, especially in summer to remove the latent load.  I went through the Handbook of Applications and the Industrial Ventilation reference manual but found no guidance that would allow the OA to be lower than that value.

When one considers that over 3/4 of that space is solid from floor to ceiling with the stacks of crates, boxes etc.  it seems a very large amount of outdoor air for the floor space that is no "solid".

Does anyone have experience with this sort of facility and reducing outdoor air levels below that 0.06 cfm/sf.


At 11:20 AM 04/03/2013, David Eldridge wrote:

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You should check with the design team to see what the governing codes are from the local authorities. In terms of ASHRAE references, 2011 Handbook of Applications Chapter 8 or Standard 170 will take precedence over ASHRAE 62.1, since the criteria in this case is for infection control purposes which goes beyond the comfort requirements in 62.1. There are a number of other references that the design team might be using. These might include the client’s own design standards which may be even higher than the regulatory requirements.

Regarding your prior post about the reheat – it will be a significant quantity, this is ttypical. However for reheat to be higher than the cooling end-use during a peak summer month should be reviewed. Assuming your location has economizer hours in the winter, the reheat could easily be higher than the cooling on an annual basis unless the design is including measures to reduce the need for reheat.

David



David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates



From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [ mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Sambhav Tiwari
Sent: Monday, March 04, 2013 3:52 AM
To: bldg-sim
Subject: [Bldg-sim] OT fresh air

Hi All,
         Is there any ACPH  recommende value for operation theatre given in ASHRAE 62  standards It is 100% fresh air AHU . but the cfm sized  is very high 6cfm/sqft as per design and if i reduce it to 3cfm/sqft i am still not getting any discomfort hour.

Thanks
Sambhav.
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>>
Christopher Jones, P.Eng.
Suite 1801, 1 Yonge Street
Toronto, ON M5E1W7
Tel. 416-203-7465
Fax. 416-946-1005
email cj at enersave.ca<mailto:cj at enersave.ca>
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