For our project, the canteen was designed with an area that would give an occupancy of 1400 people if we were to follow the default ASHRAE 62.1 occupancy, which is very high given the fact that about 2000 occupants are expected in the whole building. As for the lobbies, the expected number of occupants is also much lower than the values given by the default occupancy of ASHRAE 62.1.
I think I read some comments that the design value needs to be within 10% of the value given by ASHRAE 62.1 in terms of occupancy, isn't it possible to do without this requirement?
Thanks.
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
March 29, 2013 - 3:20 pm
Jean, see note 4 of Table 6-1 in ASHRAE 62.1. It says "Default occupancy density: The default occupant density shall be used when actual occupant density is not known.". You should input the number of occupants that you are actually designing the space for. I have not ever heard of a 10% requirement for the occupant density.
Jean-Baptiste Noel
ESD Operations ManagerGreen & Global Consulting Pte. Ltd.
8 thumbs up
April 2, 2013 - 1:08 am
Hi Andrew,
Thanks a lot for your answer. I guess I just got confused reading Paula's post (12th March) for which there were some discussions about a 10% requirement.
So, as long as the owner declares the number of occupants for those spaces, that is the number we should base the fresh air calculations on, even if much lower than the ASHRAE 62.1 default value.
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
April 2, 2013 - 1:24 pm
Yes, and it should be within 10% of the FTE number.
Srimannarayana NCVK
ESD Consultant18 thumbs up
August 13, 2013 - 3:25 am
Andrew, Jean
For one of my LEED CI project, FTE is 430 and peak occupancy is 470.
Apart from workstations, the project has two training rooms each with a occupancy capacity of 60 and a cafeteria which has a capacity to hold 130.
Fresh air requirements have been designed accordingly.
When I report the above occupancy in VRP calculations, overall occupancy becomes 680 (430+60+60+130) which is not matching with peak occupancy 470.
Please note that training rooms will be used by internal staff and their is no external training. So at any point of the day, in office, the peak occupancy will be 470 including the transient visitors.
We have been asked the reviewer to justify the occupancy discrepancy.
Request your inputs.
Thanks
Sriman
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
August 13, 2013 - 6:10 am
Thank you for a very well stated question. The answer is very simple. Just use a diversity of 70% and your occupancy will change to 476 which is within the limits of what USGBC requires.
Srimannarayana NCVK
ESD Consultant18 thumbs up
August 13, 2013 - 6:22 am
Thanks for the swift response Andrew.
Will revert to you if in case of any further queries.
Thanks
Sriman
Srimannarayana NCVK
ESD Consultant18 thumbs up
August 13, 2013 - 6:49 am
Andrew,
Training rooms have dedicated fresh air supply and seating is fixed.
Office & Cafeteria spaces are supplied by AHU's.
So i will apply diversity factor only to cafetria and office occupancy but not to training rooms?
Is my approach right. Please let me know.
Thanks
Sriman
Andrew Mitchell, P.E.
PrincipalMitchell Gulledge Engineering, Inc.
LEEDuser Expert
126 thumbs up
August 13, 2013 - 7:20 am
Sriman, there is a diversity factor at the top of the spreadsheet for population. Change it from 100% to 70% and you will be finished.
Srimannarayana NCVK
ESD Consultant18 thumbs up
September 10, 2013 - 6:49 am
Andrew,
Request your rescue again.
we have submitted VRP calculations for a project here in India.
Ventilation rate is provided inline with ASHRAE 62.1-2007. Rest rooms are provided with exhaust air systems meeting ASHRAE requirement.
GBCI has asked to include all occupiable spaces in VRP calculations. Logically toilet is a occupiable place. So I'm wondering how to fill exhaust rate calculations in VRP sheet for Toilets.
Also, toilet exhaust is carried out by transfer air and their is no fresh air supply to rest rooms.
Appreciate if you can let me know how to comply with documentation.
Thanks
Sriman