Energy modeling for unconditioned human occupied spaces

The instructor is on the right track, but is wrong.

Appendix G requires that all "conditioned" space be simulated with both heating and cooling, even if one of those systems is missing in the actual design. (Table G3.1.1.b.) But "unconditioned" spaces do not have to be simulated.

Check the definition of "conditioned" space carefully - even a small amount of heat may trigger a space being considered "conditioned". For example, we recently modeled a firehouse with some unit heaters in the equipment bay. Because we were just over 15 BTUH/FT2 capacity, we had to treat the equipment bay as conditioned space, and had to model it with both heating and cooling. (In this case, yes, set your cooling set point very high, so it doesn't turn the AC on in the model.)

A building would only be considered "unconditioned" if it had no cooling and a heating system with a capacity smaller than 3.4BTU/sq.ft. At that point the only building elements that would not need to comply with the standard are the building envelope elements all other provisions of the standard would still apply.
Standard 90.1 has no provisions for classifying a building based on spaces within the building being "occupied" or "unoccupied" so technically in the right climate a building could be classified as unconditioned if it met that definition regardless of its occupancy. However from an analysis standpoint you would not be able to compare an unconditioned building to a conditioned building and claim it was significantly more energy efficient because the baseline is conditioned.

...and the case Christopher lays out is the reason why the methodology USGBC has prescribed for demonstrating compliance with ASHRAE 90.1 is fundamentaly flawed.
Appendix G was never intended as a methodology for demonstrating code compliance with ASHRAE 90.1 yet USGBC has by de-facto allowed it to be used for that purpose.
The intent of requiring both heating and cooling systems to be modeled is for the sole purpose of preventing a building from being built without air-conditioning in order to demonstrate code compliance or I would argue increased energy performance, only to have it added back in at a later date when the now existing building no longer has to be considered in the evaluation of energy code compliance. In the case of the fire hall example, they can come back a year after finishing that project, add air conditioning and cool the space to 75F and the energy performance of that building is now much worse. This is a game that has been played before and will continue to be played, that is why the Standard is written the way it is.
The solution is a baseline system type that is considered "heating only" and a list of space types to which it can be applied. All other space types needing to be modeled with cooling systems and setpoints that provide a level of thermal comfort suitable to comply with ASHRAE 55. I suppose another exception could be an analysis showing a space can provide adequate thermal comfort without a mechancial cooling system.

I was searching for an answer to a similar question, I stumbled across this posting. In reading through all of the threads regarding this topic, I gather there is still some confusion regarding whether or not a space (conditioned or not) is to be included in the simulation.

Just to describe my situation, I was trying to determine what system type I should use as a baseline comparion to my proposed design. The building is new construction with a floor area of 25,000FT2 on the dot. Two spaces within the building are a warehouse and a machine shop which are ventilated and provided with electric unit heaters only to maintain 40F temperature in the winter season. The warehouse and the machine shop have overhead lighting and include process loads. My climate zone is 2A.

In reading Table G3.1 Part 1. Design Model, Subpart a seems to list all energy consuming portions of the proposed building that I can think of. Subpart b is an additional requirement but not conditional to Subpart a at least in my interpretation.

In trying to determine if I should model the full 25,000FT2 or just model the 25,000FT2 minus the two ventilated / heated spaces, I flipped back to Section 2 "Scope" for guidance.

Now, you may wonder why I am flipping back to that section when LEED 2009 EAp2 does not specifically reference that portion of ASHRAE 90.1. Well, in my view portions of a document do not necessarily constitute the full intent of a standard and should not be interpreted in partial context. So, in reading Section 2 of ASHRAE 90.1-2007, Part 2.2 Subpart a and Subpart b are not conditional to each other and stand alone. Further, Subpart a and Subpart b seem in encompase all energy consuming portions of a building. Section 2 Part 2.4 allows exemptions for certain other buildings or elements of buildings but only where specifically noted throughout the Standard. I could not find an exemption in the remainder of the Standard for the warehouse or the machine shop so I am left thinking that those spaces must be simulated not necessarily for the envelope components which is dependent on the heating output limitations (3.4Btu/hFT2) but rather for all other energy consumption (i.e. lights, exhaust fans, process loads,etc).

In addition, I went back to Requirements in LEED 2009 EAp2 and read the second bullet which states to include all energy costs associated with the building project. So, regardless of a conditioned/non-conditioned space(s) the energy consumption still needs to be included in the simulation.

Some simulation software may require an HVAC system in order to include total energy consumption but without including the cooling or heating associated with a particular system. This is the case with HAPv4.5.

Let me know if you think that I am off base.

I'm too much confused about what you are saying about "conditioned" and "unconditioned" space. Can anyone from the beginning explain the definitions of this words??

english is not my native lang. And you know, I supposed that "conditioned" is just the space with air conditioning; other things as heating/ventilating can exist or not, and it's separated things.

Armen, "conditioned" means that the space is heated, cooled, ventilated, etc., whether though a natural or mechanical system. "Unconditioned" means that the space is not heated, cooled, etc.

I very much understand the struggle of Yusuf. We are certifying a lot of buildings in Europe, which are usually not cooled and only natural ventilated. They do not add cooling later nor to they add fans. This is just how they do it over there and they are very confortable in their spaces. Nevertheless we have to simulate these buildings assuming cooling, because of LEED requirements, which really misrepresents the efficiency of these buildings. I think there should be the possibility to model both design and base building without cooling, if the unmet load hours do not exceed a certain number.
Going back to the question above, per my past experience and discussions with reviewers and the GBCI I think you will have to model the building to be heated and cooled and than use the exceptional method to show your saving with not using heating and cooling, but you can only claim savings, if you proved that the spaces will be comfortable for building occupants (temperature, humidity). This is basically what they told me, when I was trying to claim savings for a not cooled, natural ventilated space. They did however except savings for natural ventilation if I set the fan in the proposed building to not run at all without having to apply an exceptional method.

This very right and must be interpreted in true sense of 90.1 under the definition of unconditioned spaces.