[Equest-users] Fwd: Re: ASHRAE 62.1 cfm/person

Chris Wark cwark at rumseyengineers.com
Tue Mar 31 16:43:11 PDT 2009

I think the difference between the office and residential OA flow rates is due to office spaces being considered more-or-less public, thus a higher criteria, and the assumption of demand control ventilation (ability to open windows) in most residences.

Is there a problem with using energy recovery between the exhaust and intake? The payback is usually less than 1 year in severe climates. 

Personally, I find most buildings underventilated. 

Christopher Wark
Project Engineer
Energy Efficient Design 
99 Linden Street
Oakland CA 94607
510 663 2070 x 239
fax 510 663 2080
cwark at rumseyengineers.com 

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of William Bahnfleth
Sent: Tuesday, March 31, 2009 10:31 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Fwd: Re: ASHRAE 62.1 cfm/person

>Date: Tue, 31 Mar 2009 13:29:57 -0400
>To: Glenn Haynes <glenn.haynes at rlw.com>
>From: William Bahnfleth <wbahnfleth at psu.edu>
>Subject: Re: [Equest-users] ASHRAE 62.1 cfm/person
>One answer is that safe and subjectively acceptable are two 
>different criteria.  The prescriptive ventilation rates in ASHRAE 
>Std. 62.1 are based mainly on occupant perception.
>The definition of acceptable indoor air quality applied in 62.1 is 
>"air in which there are no known contaminants at harmful 
>concentrations as determined by cognizant authorities and with which 
>a substantial majority (80% or more) of the people exposed do not 
>express dissatisfaction."  Fanger and others conducted research that 
>relates ventilation rate to percentage dissatisfied for human 
>bioeffluent and building emissions that are generally consistent 
>with ASHRAE's values.
>I do not understand the comment about LEED, since extra credit is 
>currently given for exceeding 62.1 by 30% or more, again, based on 
>research that indicates people are more satisfied and productive at 
>higher ventilation rates.
>Bill Bahnfleth
>At 01:03 PM 3/31/2009, you wrote:
>>What I am about to say may be controversial, but I am a 
>>conservation program impact evaluator, an avid DOE2 user, and feel 
>>strongly about excessive OA ventilation requirements, especially in 
>>colder climates.  The ASHRAE minimum, when translated into air 
>>changes per hour (ACH) requires over 0.8 ACH for a 10x10 office 
>>with an 8 foot ceiling and one occupant.  On the other hand, the 
>>EPA claims that Energy Star homes must have an energy recovery 
>>ventilator because they often end up with natural infiltration 
>>rates under the threshold of safety, about 0.32 ACH.
>>If, as they believe, 0.32 or higher is safe enough for residential 
>>occupants, why, then, does the ASHRAE standard require almost three 
>>times that for office spaces?  This high requirement is, of course, 
>>safe enough, but it is costing commercial building operators in 
>>cold climates a fortune in heating costs, often accounting for 50% 
>>to 80% of the total heating energy consumption.  In hot climates it 
>>translates into excessive cooling energy use.  Is it time for some 
>>of us to question the ASHRAE standard, or is the EPA threshold (it 
>>isn't a law) safe enough?
>>With the current emphasis on LEEDS design are we overlooking a huge 
>>energy savings potential here?  We strive very hard to save as much 
>>energy as possible, but then we are required to impose a 
>>questionable ventilation standard that often overshadows all else.
>>I just want to hear some other professional thoughts on this.
>>Glenn C. Haynes, PE
>>Middletown, CT
>>-----Original Message-----
>>From: equest-users-bounces at lists.onebuilding.org 
>>[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Min-Hwan Yang
>>Sent: Tuesday, March 31, 2009 12:08 PM
>>To: equest-users at lists.onebuilding.org
>>Subject: Re: [Equest-users] ASHRAE 62.1 cfm/person
>>I think what Pravin did was correct.
>>Eric, according to DOE2.2 Dictionary, only the maximum value of 
>>oa-flow/area and oa-flow/per will be used, not summed together.
>>Please let me know if I am wrong.
>>Min-Hwan Yang, CPD, LEED AP
>>Mechanical Engineer | yangm at kjww.com
>>200 West Jackson Boulevard, Suite 1200 | Chicago, Illinois 60606
>>312-294-0501 | Direct: 312-356-3750 | Fax: 312-294-0003
>>I'm attaching a screen capture from a building I modeled (yes, that 
>>system setup was heinous and produced terrible results - it wasn't 
>>my doing) that shows the OA settings based on 62.1 requirements.
>>Let me know if that doesn't simplify your process.
>>From: equest-users-bounces at lists.onebuilding.org 
>>[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pravin Wakode
>>Sent: Tuesday, March 31, 2009 4:50 AM
>>To: equest-users at lists.onebuilding.org
>>Subject: [Equest-users] ASHRAE 62.1 cfm/person
>>Hi All,
>>         This query is related to HVAC Ventilation used in equest. 
>> As per ASHRAE 62.1 Ventilation rates are specified based on per 
>> person and per sqft basis for example if I consider a office area 
>> the ventilation rates would be 5 cfm/person + 0.06 cfm/sqft.
>>Equest doesnt allow you to enter the ventilation rate based on sqft basis.
>>I  am calculating the ventilation rate manully (using per-person + 
>>per-sqft basis) and then dividing it by total occupancy and 
>>arriving at the cfm/person value which is to be entered in Equest.
>>Is this procedure correct???
>>Pravin Wakode
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William P. Bahnfleth, PhD, PE, FASHRAE
Professor of Architectural Engineering and Director, Indoor Environment Center

Penn State / 104 Engineering Unit A / University Park, PA 16802 USA
voice: 814.863.2076 / fax: 814.863.4789 / e-mail:  wbahnfleth at psu.edu
http://www.engr.psu.edu/ae/faculty/bahnfleth/ , http://www.engr.psu.edu/ae/iec

Only the ideas that we really live have any value. - Hermann Hesse 

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