I’m modelling a hotel in which three floors are occupied by rooms (residential, tot. area 733m^2) and two floors (one underground) are occupied by services and a wellness centre (non-residential, tot. area 1060.2m^2). If I considered only the residential spaces, according to Table G3.1.1A I should use System 1 – PTAC. If I considered only the non-residential areas, according to Table G3.1.1A I should use System 3 – PSZ-AC. A note of that table states: “Where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building”. Because of the larger surface, I would consider non-residential spaces as predominant. Shall I model System 3 – PSZ-AC? Or shall I consider that the floors are five and therefore shall I model System 5 – Packaged VAV with Reheat?
With Regards
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 17, 2012 - 9:25 am
While I do not agree with this methodology, this is the way the GBCI reviewers have been instructed.
Enter Table G3.1.1A based on the area of the non-residential, so a system 3. Then apply the residential exception under G3.1.1(a) and model PTACs for the residential areas.
My opinion would be to enter Table G3.1.1A with the whole area, so a system 5 and then apply the residential exception to those areas.
Either way would likely be accepted.
Francesco Passerini
engineer90 thumbs up
September 17, 2012 - 11:27 am
Thank you Marcus, but in my case area of nonpredominant conditions is less than 1900m^2 (it is 733m^2), therefore I cannot apply exception G3.1.1(a). I would model System 3 for whole area. Would this solution be accepted?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 17, 2012 - 12:05 pm
I did not do the conversion so yes if it is less than 20k sf exception a is not available. Exception b applies and gives you the same system 3. So a system 3 across the whole building makes sense.
Steven Er
11 thumbs up
September 19, 2012 - 3:42 am
ASHRAE 90.1 2007 user manual, pg G-23 states "If a building has both residential and nonresidential spaces with their total conditioned floor area both greater than 20,000 ft2 (1,900 m2), then the HVAC system type is determined separately for the residential and nonresidential portions".
ASHRAE 90.1 2007, Appendix G, Table G3.1.1A, footnote states "where attributes make a building eligible for more than one baseline system type, use the predominant condition to determine the system type for the entire building".
This mean to me, if a building mixed with residential and nonresidential that has total conditioned area less than 20,000 ft2 (1,900 m2), baseline HVAC system for entire building shall be determined based on predominant condition. In this case, use nonresidential area and apply system 3 for entire building.
Any suggestion?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 19, 2012 - 9:10 am
Sounds correct to me.