As baseline model I have to model System 6 according to Table G3.1.1A. On a floor the spaces that have windows are naturally ventilated while the internal spaces are mechanically ventilated. G3.1.1 states that "For system 5, 6, 7, and 8 each floor shall be modeled with a separate HVAC system". I think that modeling only one AHU for the whole floor would be inappropriate, because in the baseline model outdoor air would be provided through the mechanical system to the whole floor (while in the proposed model only some spaces are mechanically ventilated). For this reason in that floor I would model two AHUs: one doesn't supply outdoor air and is connected only with spaces that are naturally ventilated. Would it an acceptable solution?
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Francesco Passerini
engineer90 thumbs up
February 12, 2014 - 12:02 pm
Another issue: the AHU that supplies air in the proposed model has an extraction fan. In the baseline model I would model one AHU with the extract fan (the AHU that supplies also outdoor air) and one AHU without extract fan.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
February 12, 2014 - 12:23 pm
Do any of the G3.1.1 exceptions apply?
Francesco Passerini
engineer90 thumbs up
February 13, 2014 - 5:14 am
In the zones that have openable windows there are offices, while the central zones are: one conference room, one restroom, one corridor. Because of the presence of people and electronic devices in the conference room I estimate an internal thermal load equal to 50 W/m^2, i.e. > 31.2 W/m^2 (exception b). Could I model a separate system only for the conference room?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
February 17, 2014 - 10:53 am
You are required to do so if the conference room meets the exception b criteria.
To your original question - You would still create one system per floor. You cannot create a separate system. Supply the quantity of outdoor air in the baseline identical to the outdoor air supplied in the proposed.