[Equest-users] Complicated school baseline system type question

[Chapin, Alex N]

Hi Steve,

Here are my responses:


1.      I think that the main baseline system should be based on the whole conditioned school area (156,000 sf). Therefore, use System Type 8. The primary system should be based on the whole building and predominant heating source condition.

2.      This question is tricky and I’m not sure if there is an official stance on how to handle this one. I would suggest going with a System type 5 and then System Type 3 for anything that meets exceptions b or c.

3.      The single zone systems should match the baseline energy source or the predominant building heat source. In this case though, when you apply exception a to the portion of the building that is heated with natural gas, then the predominant heating source for that portion is natural gas. But to answer your specific examples, the small server room would be conditioned with a DX natural gas furnace and the kitchen should be an electric heat pump unless it is greater than 20,000 sf. Also note that if there is a dedicated makeup air unit for the kitchen range hood that is natural gas, then that should be modeled the same in the Baseline and Proposed based on the proposed design. This is because the makeup air unit serves a process load (range top cooking heat/smoke removal) and not an occupant load. Additionally, even though you might think that the server room system is also only serving process loads, people do need to occupy the server room space to maintain and update the servers, so it isn’t the same as the makeup air unit which is only serving the ventilation used to makeup the exhaust from the range hood.

Thanks,
Alex

Alex Chapin EIT, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
A Day & Zimmermann Company
O 804.521.7072
4880 Sadler Road, Suite 300 | Glen Allen, VA 23060
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From: Steve Jacobs [mailto:sjacobseng at gmail.com]
Sent: Sunday, November 15, 2020 9:57 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Complicated school baseline system type question

I am modeling a school that is 156,000 SF under 90.1-2007. The majority of the school is treated with electric heat pumps but about 26,000 SF of the building is heated with natural gas furnaces.

So the approach I would take is that the predominant condition is electric heating, so that should be the main baseline system type. Then per G3.1.1(a) the natural gas systems are large enough to have their own baseline system.

My first question is do you think the main baseline should be based on the whole school area of 156,000 SF, or the 130,000 SF. This is the difference between system type 6 or 8.

Then, the 26,000 SF is large enough to qualify for the system type 5. But most of these spaces are large single zone systems (i.e. cafeteria, gymnasium, ect). And some could qualify for the single zone exceptions. Which would bring the area under 25,000 SF. How would you account for this area?

And in general if spaces qualify for exceptions in G.3.1.1(b) or G3.1.1(c) do you think the single zone systems should match the baseline energy source or the proposed building energy source. For example if you have a school that is heated by natural gas, but you have a small server room that is conditioned with an electric heat pump. Should the baseline system in that single zone system  be electric? Or an electrically heated school with natural gas in the kitchen. Should the kitchen single zone system be natural gas like the proposed or electric because that is the baseline fuel source.

I couldn't find any clarifications to this issue, but if there has been any official guidance please let me know.

Thanks in advance,
Steve
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