We have a project that is a parking garage structure. All of the enclosed circulation, storage and restroom areas are provided with natural ventilation via operable windows and no air conditioning systems. However, there are four small rooms (about 140sq.ft. each) used as offices and they are provided with ductless split systems and operable windows for natural ventilation as the ductless systems are not really equipped to take and condition outside air. To show compliance with EAp2 and EAc1 we are planing to model only the areas provided with a/c thus the four offices. I was wandering if anybody had a similar situation where the space is provided with a/c and is relaying on operable windows for natural ventilation and how the outside air is modeled. My appriach is to model the same amount of OA (the minimum required by ASHRAE) in the baselinaand proposed wich would be in accordance with Appendic-G 3.1.2.5. I know is hipotetical, but what other approachcould I take? Would we need an interlock to shut down the a/c unit when the window is opened or do something special from energy consumption stand point?
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Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
July 21, 2011 - 12:09 pm
For the energy simulation you have to model with the baseline mechanical systems also inplace for your design case model. Put the fancoils in as additional with priority 1, baseline system priority 2. The baseline will then kick in when your system does not meet the ventilation or heating cooling requirements. The baselines model's windows don't open.
If you have a naturally ventilated occupied space you should seperately proove that natural ventilation is sufficient (i.e. with a simulation or calculation). you can use the results in the energy simulation for ventilation rates through windows, but watch out that you don't let in too much outdoor air through the windows, else the design case will be more energy expensive.
Christopher Schaffner
CEO & FounderThe Green Engineer
LEEDuser Expert
963 thumbs up
September 8, 2011 - 11:04 am
FYI - check the LEED Minimum Program Requirements. Parking structures are not eligible for LEED Certification.