MINIMUM IAQ AND FTE

FTE is required when performing this prerequisite for existing buildings, not new construction.

I have seen USGBC review comments saying that the occupant load with diversity should be within 10% of the FTE for ASHRAE 62MZ calculations. That, to me makes logical sense fr most buildings. If the two are not within 10% for some reason (i.e. I did not calculate spaces that were not considered to be potentially critical) then I always include that as a comment in the template.

The USGBC's LEED Department linking of FTE to ASHRAE 62.1, and the automatic assumption that heating is the dominate ventilation mode for conference rooms, does not take into account that heating occurs during low diversity, and cooling occurs during high occupancy. ASHRAE 62.1 should consider occupancy based on expected occupancy. I have that case for a building with a current FTE of 1 per 1,000 sf. The FTE might increase in the future, but that depends on the business climate. The building has seven ventilation systems. We are using the default ASHRAE 62.1 occupancy densities rather than actual FTEs. This makes more sense than using actual FTEs.

Hernando, it sounds like you are using a reasonable approach to your design. I would just go ahead and explain why it differs from the FTE. I have never seen them comment on it unless your 62.1 calcs show a lower occupant load than the FTE's.

Tristan, even though the FTE is not referred to in the Reference Guide it does appear as a review comment if the total occupancy used in for ASHRAE 62.1 is not consistent with the PI Form FTEs. I think this only occurs when the FTE is lower for ASHRAE 62.1, and not when it is higher.

Andrew, I am relatively certain this only occurs with low ASHRAE 62.1 FTEs. What triggers the review response, like other LEED responses, is that it is not explained in the LEED Reference Guide. I can't find a published reference to the 10% difference in occupancy counts. Yet, it is required.

this occcupancy has to be the same used for the energy modeling？ Can anybody confirm the above?Thanks,

The ASHRAE 62.1 occupancy (including diversity) should be within 10% of the project FTE. You should use the EAp2 forum to ask the question of whether or not the energy model needs to be within any percentage of the FTE occupancy.

when you talk about within 10% of FTE, you actually mean total building users at peak moment (see PI F3) by FTE, right?

No, I mean FTE as in the full time equivalent occupants. The peak total could be much higher than what you need to use for ventilation design. If you familiarize yourself with ASHRAE 62.1-2007 then you will find that you design ventilation for the number of occupants normally in a space. In a large space of intermittent occupancy you may use a time average based on the equations in the standard. Your ventilation occupancy load will (for most buildings) reflect the FTE number +/- 10%. If you are higher due to an unusually high number of transients then just explain that in the template. You should never submit if you are more than 10% lower though.

Thanks, Andrew. For a project with 35 FTEs and over 300 transiets at peak moment, Although the ventilation occupancy adjusted by diversity factor and/or time average would still be far beyond FTEs, submitting with explanation may work, do i get it right?

Yes, just explain this on the form.

Weidong Luo, yes, as Andrew says just explain in a narrative how your design occupancy for IEQp1 is related to the number of FTEs and transients. As long as you have a reasonable explanation that is consistent with what you have stated in other credits, it should be accepted. As a general comment on this topic, I see this statement in the LEED project submittal tips for NC2009 IEQp1: "Be sure that the total peak occupancy and square footage documented for this credit is reported consistently across all credits." The LEED Project Submittal Tips for several 2009 rating systems can be downloaded at: http://www.gbci.org/main-nav/building-certification/resources.aspx