[Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoorairsupply

Brahme, Rohini UTRC BrahmeR at utrc.utc.com
Thu Nov 12 09:13:56 PST 2009


Since we are on this topic, I had a question on definition of occupancy.

I havn't read the standard in detail, but isn't there a requirement of
some OA/sqft in addition to OA/person. 

Let's assume that an office is assumed normally occupied from 8 am to 6
pm -  Then during unoccupied hours (6.01 pm to 7.59 am) can the OA be
zero or should it be OA per sqft?

More tricky, let's say we have a occupancy sensor and know that the
office is unoccupied from 12.00 pm to 3 pm (during the regular office
times). What is the OA at this time - 0 or OA/sqft?

Thanks

-rohini

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Thursday, November 12, 2009 11:36 AM
To: Guin, Michael; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum
outdoorairsupply

 

No.

 

Refer to Section 5.4: 

"Mechanical ventilation systems shall include controls, manual or
automatic, that enable the fan system to operate whenever the spaces
served are occupied.  The system shall be designed to maintain the
minimum outdoor airflow as required by Section 6 under any load
condition."  

 

In summary, you must provided the minimum ventilation rate as prescribed
in Chapter 6 only when (A) the space is occupied and (B) there's a
thermal load condition (or manual control - see Section 5.4) triggering
the operation of the ventilation system.

 

Your original question is confusing to at least a few of us because of
stating an office ceases to be a "zone" at night...  It's a terminology
thing, but 62.1 and other standards will become more digestible to you
when you recognize that's not the case.  The clarification we're making
here is that where a zone occupancy (i.e. "office") is decided and a
constant over time, something like "occupancy rate" can be variable.

 

I'd like to also point out, based on your first inquiry, that the
equation at 6.2.2.1 uses maximum zone occupancy to establish the minimum
design OA rate, not the hourly occupancy rate (which may be zero).

 

~Nick

 

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

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 Guin,
Michael
Sent: Thursday, November 12, 2009 8:44 AM
To: Shawn.Lee at fluor.com
Cc: bldg-sim-bounces at lists.onebuilding.org;
bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoor
airsupply

 

is there any requirement to provide minimum outdoor fresh air wihin the
office space when it is unoccupied according to ASHRAE 62.1

 

Do you think it it clear enough? 

Regards

Michael

________________________________

From: Shawn.Lee at fluor.com [mailto:Shawn.Lee at fluor.com] 
Sent: 12 November 2009 13:58
To: Guin, Michael
Cc: bldg-sim at lists.onebuilding.org;
bldg-sim-bounces at lists.onebuilding.org
Subject: Re: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoor air
supply


Michael, 

Technically answering your question may not help you much.  You need to
make the question clearer and more meaningful.  Tell people what you are
trying to do, what is in your mind, and what you are trying to
accomplish.  Then this group may help you more on the target. 

Thanks. 

Shawn Lee, PhD, PE 



	"Guin, Michael" <Michael.Guin at WSPGroup.com> 
Sent by:  bldg-sim-bounces at lists.onebuilding.org 
11/12/2009 06:09 AM 

To

<bldg-sim at lists.onebuilding.org> 

cc

	
Subject

[Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoor air supply 

 

		





Dear all, 

ASHARE 62.1 2007 deifned zone as an occupied space. Table 6-1 provides
the calculation for different spaces based on occupancy and floor area
of the occupied space. 

If we consider an unoccupied office space at night (i.e. not strictly a
"zone  anymore" ); is there any requirement to provide minimum fresh air
wihin the office space. 

Thanks in advance for your help 
Michael   

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