I have a roughly 48,000 sf church with the following breakdown by area and hours of use:
1st Floor:
4,100 sf Multipurpose Space used 16 hours per week
8,200 sf Common Space used 72 hours per week
7,500 sf Worship Space used 12 hours per week
4,300 sf Office Space used 50 hours per week
14,700 sf Classroom/Storage Space used 0 to 4 hours per week
2nd Floor:
9,300 sf Classroom/Storage Space used 0 to 4 hours per week
Half of the total building area is Classroom/Storage Space with only 0 to 4 hours of use per week, while the hours vary from 12 to 72 hours per week for the other half of the building. It isn't clear to me which parts of the building should be considered the predominant case. Four hours per week is significantly different than 72 hours per week, but when you start to compare the other spaces the difference narrows quickly. Should I just say anything over four hours gets grouped together as the predominant case? But if I do that, there is still half of the building left as the non-predominant area.
Advice would be greatly appreciated. Thanks!
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
August 8, 2013 - 6:36 pm
Further expanding on my above post...
The Common Space (8,200 sf) and the Office Space (4,300 sf) are the only areas open almost all week long. The remaining 35,500 sf is only occupied one or two days per week for up to 16 hours total for the week. I feel this 35,500 sf is the predominant case and should be modeled as a VAV system (one for the first floor and one for the second floor).
However, I received a preliminary review comment saying the Classroom/Storage areas should be considered the non-predominant case which totals about 24,000 sf. The rest of the building totals about 24,000 sf also. Correct me if I'm wrong, but I believe it was recently decided the total building area shall not be used to decide the system type of the predominant case. That means neither case meets the 25,000 sf requirement for a VAV Baseline system which I was counting on. Thus now I have to compare our Single Zone design to a Single Zone baseline design. A quick analysis in HAP shows a 5-point decrease in LEED points.This is very discouraging at this point in the game. Any advice?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
August 9, 2013 - 10:20 am
I assume you are trying to apply Exception b to G3.1.1 correct? In that case the spaces need to differ by at least 40 hours/week. Because the spaces vary in hours if you are lumping spaces with different hours of use together you could try to do a weighted average to compare hours in lightly vs heavily used areas.
If you are in the middle of the review process then I would suggest that you do what the reviewer is telling you to do. Sounds like they are telling you to model a system 3/4 in the whole building. Are you electric or gas heat? The decrease makes sense if going from a 6 to a 4 but does not make sense if going from a 5 to a 3.
You are correct - you remove the square footage you are applying G3.1.1 exception to and use the remainder when entering Table G3.1.1A. Single zone to single zone does sound like a fair comparison.
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
August 9, 2013 - 11:34 am
My proposed design is a combination of gas fired packaged rooftops and split system heat pumps with gas furnace backup. My baseline system was Type 5 with several Type 3 systems for the exceptions.
The reviewer didn't directly mention any changing of system type; just that the areas with significantly more hours should be considered the predominant case and the areas with very few hours should be the exception. My argument is that the majority of the building is hardly occupied throughout the week so that should be the predominant case. The part of the building that is occupied frequently is a much smaller portion of the whole and therefore should be the exception.
I had previously interpreted the Appendix G requirement to be based on predominant square footage, not predominant hours of occupancy. But another gray area under the exceptions is the minimum 20,000 sf requirement under exception a. Does Exception a trump all of the other exceptions or is it just one possible exception? In other words, even if a space varies by more than 40 hours of use from the majority of the building, can I only take exception for it if the space takes up at least 20,000 sf of the building?
In regards to hours differing by more than 40 hours per week and lumping varying hours together to form a set of heavily occupied hours vs. lightly occupied hours would the following work:
Lightly Occupied group:
14,700 sf 1st Floor Classroom/Storage Space used 0 to 4 hours per week
9,300 sf 2nd Floor Classroom/Storage Space used 0 to 4 hours per week
7,500 sf Worship Space used 12 hours per week
4,100 sf Multipurpose Space used 16 hours per week
Weighted hours = 7 hours/week
Heavily Occupied group:
4,300 sf Office Space used 50 hours per week
8,200 sf Common Space used 72 hours per week
Weighted hours = 64 hours/week
So 26% of the building area has 64 hours of occupancy per week while the remaining 74% of the building has 7 hours of occupancy per week. Again should the predominant case be based on the hours of use or the square footage?
Thanks!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
August 9, 2013 - 3:23 pm
Predominant should be based on area, not occupancy.
I do not think Exception a applies in your case since your heating source is fossil fuel throughout the building.
Predominant is area so I think the lightly occupied should be predominant and the exception applied to the heavily occupied.
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
August 12, 2013 - 11:06 am
Ok so you're saying exception 'a' does not apply, but exception 'b' still does, correct?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5912 thumbs up
August 12, 2013 - 11:25 am
Yep, looks that way to me.