Table G3.1 in Appendix G requires only conditioned space be simulated as being both heated and cooled in the proposed design. The 90.1 User's manual further explains that a heated-only or cooling-only building would need to be modeled as being heated and cooled. Unconditioned spaces would have neither heating nor cooling systems. However, Appendix D in the Advanced Energy Modeling for LEED - Technical Manual outlines a modeling methodology in which an unconditioned, naturally ventilated building is simulated as having a heating and cooling system in its proposed design. Doesn't this contradict the language in ASHRAE 90.1? Wouldn't a naturally ventilated building (no heating and no cooling either directly or indirectly via an adjacent space) be defined as unconditioned? We have a project that is a seasonally occupied park district facility (1700 SF) housing a concession stand, single workstation, storage, janitor's closet and toilet facilities that is struggling with its definition and modeling methodology for EAc1.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
August 16, 2013 - 9:02 am
Yes there is a contradiction but you just have to get over that :-).
The problem is that there are climates in the world that do not require heating or cooling systems to maintain an acceptable level of thermal comfort. The methodology in Appendix D has been deemed by the rating authority mentioned in Appendix G (USGBC) to be an acceptable one to be used for applicable circumstances.
So in your case it sounds like no heating or cooling but the facility is not occupied during the heating season. Assuming that is the case you are supposed to model a cooling system according to Appendix G. A common workaround is to set the cooling temperature so high that it never comes on (t-stat setting just need to be identical in both models). This is pretty simple as long as you are not trying to claim any savings credit for natural ventilation.