[Bldg-sim] ASHRAE 62.1 unoccupied space minimum outdoorairsupply

[Karen Walkerman]

Ok, this makes more sense.  What about corridors that have only transient
and very low occupancy rates?  Can this also be classified as unoccupied?

Thanks,

--
Karen

On Thu, Nov 12, 2009 at 2:07 PM, Nick Caton <ncaton at smithboucher.com> wrote:

>  I may be wrong, but it appears a number of people aren’t examining the
> equation in 6.2.2.1 as I’m suggesting.  If you’ll check that out I’m certain
> you’ll find this is a much simpler question/answer than it’s being made out
> to be.
>
>
>
> *Both* sets of figures provided in Table 6-1 (OA/person and OA/SF) are
> used to determine the design minimum OA rate, using 6.2.2.1’s equation.
>  Occupancy has no effect on the OA/SF requirement, and likewise zonal area
> has no effect on the OA/person requirement.  Additionally, the occupancy
> figure used is the *maximum* occupancy of that zone.  Quoting  6.2.2.1:
> “Pz = zone population: the largest number of people expected to occupy the
> zone during typical usage…”  It is not the hourly percentage occupancy and
> is not zero unless the space is never normally occupied (as with a storage
> room like Karen suggested).
>
>
>
> The design minimum OA rate is only applicable when the ventilation system
> is operating.  Unless I’m missing something major, the ventilation system is
> not required by ASHRAE 62.1 to operate 24 hours per day  (again, refer to
> Section 5.4, which I’ve copied entirely below).
>
>
>
>
>
> I’ll try to break down the current questions/statements on the table:
>
>
>
> The reason I had the question was because I think OA/sqft technically
> should not be dependent on occupancy…
>
> That’s a fair judgement a designer is allowed to make.  The 62.1 Standard
> is just that – not a code, but a set of suggestions provided by some of
> those best qualified to provide them.  To play the devil’s advocate, the
> counter-argument is that Occupancy cannot be ignored by an energy-conscious
> ventilation system designer.
>
>
>
> …If that was the case, it would suffice to just increase the OA/sqft and
> have only one number to take care of.
>
> Someone doing that would be ignoring the equation Table 6-1 was built
> around (re: 6.2.2.1).  I’d agree that would be a misinterpretation of the
> standard.
>
>
>
> 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.
>
> OA/SF is always used alongside OA/person to determine the “breathing zone
> outdoor airflow.” (Which I’ve been calling the design minimum OA rate).  The
> question of when these ventilation rates apply is tied to when the zone is
> occupied.  To restate my position (Again Ref: Section 5.4):  ASHRAE 62.1
> does not require that ventilation systems operate during unoccupied times.
>
>
>
> What do the hvac designers specify for the control of OA?
>
> Not sure whether a concise answer can be provided to this broad question…
> OA ventilation *can* be controlled by any combination of
> scheduling/occupancy sensing/timer control/temperature/humidity/VOC, CO2, CO
> or other air quality sensors… all depending on the project budget, climate,
> and type of system being designed.  If this question had a simple answer,
> then we wouldn’t need HVAC designers =).
>
>
>
> 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.
>
> See my answer above.
>
>
>
> So do you need this ventilation rate only when the building is occupied,
> only when the space is occupied, or all the time?
>
> Strictly speaking, only when the zone (space) is occupied.  If you have a
> one-zone system that doesn’t distinguish between occupancy rates, then
> whenever the building is occupied.
>
>
>
> 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?
>
> This is a broad-scope question, so I’ll add another quote under Section 1,
> entitled “PURPOSE:”
>
> *“1.1*        The purpose of this standard is to specify minimum
> ventilation rates and other measures intended to provide indoor air quality
> that is acceptable to human occupants ant that minimizes adverse health
> effects.”
>
> If a space is never occupied, then ASHRAE doesn’t care about air quality.
> If a space is “almost never occupied,” then they do.  To continue your
> example, if you have a storage warehouse with no ventilation installed, and
> it’s almost never occupied, someone might eventually store something in that
> space that without ventilation would eventually cause a health hazard to the
> next occupant entering the space.  In my college years, this was a commonly
> observed effect caused on a small scale by my roommates forgetting food in
> the microwave =).
>
>
>
> ~Nick
>
>
>
> ~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:* Karen Walkerman [mailto:kwalkerman at gmail.com]
> *Sent:* Thursday, November 12, 2009 12:28 PM
> *To:* Brahme, Rohini UTRC
> *Cc:* Nick Caton; bldg-sim at lists.onebuilding.org
>
> *Subject:* Re: [Bldg-sim] ASHRAE 62.1 unoccupied space minimum
> outdoorairsupply
>
>
>
> 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
>
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