[Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoorairsupply

[Karen Walkerman]

Ok, so here's a question - what happens when you have a space that is almost
NEVER occupied, but has a cfm/sf requirement - like a storage room with a
requirement of 0.12 cfm/sf.  This is a pretty high outdoor airflow,
especially if you're just storing old files.

So do you need this ventilation rate only when the building is occupied,
only when the space is occupied, or all the time?

If you only need the ventilation when the space is occupied, and it is
almost never occupied, why install the ventilation in the first place?


--
Karen


On Thu, Nov 12, 2009 at 1:11 PM, Brahme, Rohini UTRC
<BrahmeR at utrc.utc.com>wrote:

>  Thanks Nick. The reason I had the question was because I think OA/sqft
> technically should not be dependent on occupancy. If that was the case, it
> would suffice to just increase the OA/sqft and have only one number to take
> care of. What I am not sure of is whether OA/sqft is used only during the
> typical occupied hours irrespective of whether it is actually occupied or
> not or is it used throughtout the day/weekend/vacation etc. What do the hvac
> designers specify for the control of OA?
>
> -rohini
>
>
>
> *From:* Nick Caton [mailto:ncaton at smithboucher.com]
> *Sent:* Thursday, November 12, 2009 12:22 PM
> *To:* Brahme, Rohini UTRC; bldg-sim at lists.onebuilding.org
> *Subject:* RE: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum
> outdoorairsupply
>
>
>
> I havn’t read the standard in detail, but isn’t there a requirement of some
> OA/sqft in addition to OA/person.
>
>
>
> You are correct.  Refer to the equation of Section 6.2.2.1 as I referenced
> below.
>
>
>
> 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?
>
>
>
> It sounds like you’re asking the same question I just answered, so I may
> not be understanding completely…  By Section 5.4 I do not believe an
> unoccupied space is required to have any OA supplied.  The equation in
> 6.2.2.1 does include a component “per square foot,” but that equation is for
> determining the design minimum OA rate.
>
>
>
> 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?
>
>
>
> Applying the same logic and the same section, 5.4, if there are controls
> that automatically determine a space is occupied and turn the associated
> system on to provide the required OA, then there’s no reason those systems
> aren’t allowed to turn off while unoccupied.  Short answer for your
> example:  0.
>
>
>
> I’ll point out, I’m merely an E.I.T. (with my head in the books) sharing my
> interpretations, so it may be worth holding out for a second opinion =).
>
>
>
> ~Nick
>
>
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *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 *Brahme, Rohini UTRC
> *Sent:* Thursday, November 12, 2009 11:14 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum
> outdoorairsupply
>
>
>
> 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
>
>
>
>
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *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
>
> _______________________________________________
> Bldg-sim mailing list
> http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to
> BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
>
> ------------------------------------------------------------
>
> The information transmitted is intended only for the person
>
> or entity to which it is addressed and may contain
>
> proprietary, business-confidential and/or privileged material.
>
> If you are not the intended recipient of this message you are
>
> hereby notified that any use, review, retransmission, dissemination,
>
> distribution, reproduction or any action taken in reliance upon
>
> this message is prohibited. If you received this in error, please
>
> contact the sender and delete the material from any computer.
>
>
>
> Any views expressed in this message are those of the individual
>
> sender and may not necessarily reflect the views of the company.
>
> ------------------------------------------------------------
>
>
> _______________________________________________
> Bldg-sim mailing list
> http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to
> BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20091112/286228ec/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: image/jpeg
Size: 1459 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20091112/286228ec/attachment-0001.jpeg>