ASHRAE 62.1 cfm/person

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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???

Regards,

Pravin Wakode

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eQuest also takes a total CFM value instead of the CFM/person value.
This is specified on the Outdoor Air tab of the Zone in the box labeled
"Air Flow". The value of this box overrides all other CFM values
entered. Just remember that eQuest applies an adjustment factor to
account for elevational differences in air density based on the
elevation entered in the Site Data form - this will cause the values in
the reports to be higher than what you entered into the Air Flow box.

Jeremy R. Poling, LEED AP

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Pravin,

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.

Eric

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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

Pravin,

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.

Eric

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Wow. You're correct.

The dictionary states:

"The maximum of values resulting from OA-FLOW/AREA, OA-FLOW/PER, and OA-CHANGES will be used unless an over-ride value for OUTSIDE-AIR-FLOW is specified."

I had read this assuming the logical operator "and" meant they were summed (rather than defining a set) and the initial portion of the statement was sloppy engineering English (as it would be the more useful of the two options). I suppose I need to be more aggressive in testing my assumptions, eh?

Thanks for correcting that!

Eric

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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

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