LEED Comments for EAC1 - Optimize Energy Performance

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Hi Ashraf,

First of all I would like to know that which software you are using for
Energy Simulation. If eQuest, go through my comments in red.

1. It is unclear whether one Baseline Constant Volume system was
modeled per thermal zone in the Baseline Case as required. Please verify
that one system was modeled per zone, and that the Baseline System
efficiency for each zone was modeled consistently with the capacity for the
Baseline System serving that zone. (please guide me how to solve this
comment)- Clarify your baseline system and Fan control type from Table
G3.1.1.A and Table G3.1.1B as per your building area or no. of floors and
also confirm that that your system efficiency meets the section

2. Section G3.1.2.9 describes calculation used to determine the fan
power in the baseline building. Please list the total fan volume,
capacities, and fan power for the Baseline and Proposed system. (As my
system doesn?t have any Return fan, so i am dividing the ASHRAE total Fan
power by 70% supply, 20% return, 10% exhaust based on my understanding.
Please guide me if any changes required)- Reviewer is not asking about the
Return fan, reviewer has asked for model the Fan power in baseline system as
per table G3.1.2.9. Thus you should model the kW/CFM in baseline system as
per formula of Baseline Fan Brake Horsepower in Table G. Please see
attached Fan power document to model the kW/CFM in eQuest.

3. Based on supporting document, supply fan volumes of some of the
zones in the baseline design appear to be modeled as ?AUTOSIZED?. For the
baseline design the fan supply volumes should be calculated based on the
system capacity and a temperature differential of 20?F, as set forth in
Section G3.1.2.8.(Please guide me Where can we enter the temperature diff,
is in Cooling Coil or any other ways.) ? As per Table G3.2.8, baseline
building design shall be based on a supply-air-to-room-air temperature
difference of 20?F. Its means that if your room temperature is 75?F then the
zone entering minimum supply temperature should be 55?F. (Excerpt attached
to model the zone entering minimum supply temperature).

Let me know if you get any other comments on this.

Ashu Gupta

ashu gupta's picture
Joined: 2011-09-30
Reputation: 0

The first comment seems like the reviewer isn't
carefully reviewing the submission. It is fairly
simple to check the proposed sim file and the
Budget case sim file to see if each zone in the
proposed case is modelled as a single zone system
in the Budget case. I have seen this comment
before and I am not sure what additional
documentation the review might want to make it "clearer".

Comment 2: I always setup a spreadsheet showing
my calculation of total fan power for the proposed case and the Budget case.

Comment 3: The 20?F differential is the
difference between the room set point and the
supply air temperature. Re Autosizing supply air
flows: I always autosize the Baseline air flows
based on the 20?F supply air to room air
temperature difference (G3.1.2.8). I set the
heat sizing ratio to 1.25 and the cool sizing
ratio to 1.15 as per G3.1.2.2. Never had a
problem with this approach. I suppose you could
do a sizing run with those sizing ratios then
explicitly enter the resulting supply air flows,
heating and cooling capacities but it would
amount to almost the same results.

Chris Jones

Chris Jones's picture
Joined: 2011-09-30
Reputation: 0

Appeasing the GBCI reviewers is always about proper documentation. They shouldn't have to go thru every zone/system in your .inp file to make sure there is a corresponding system. Hell, it's hard enough for us to do that (without being able to open up eQuest).

Comment #1: Plain and simply state: The baseline building has been configured so that each thermal zone has a corresponding system, and the thermal zones for the baseline building match the proposed building. (and you just need to make sure this is the case - if you have an unconditioned zone attached to a system, you might want to say that the unconditioned zone has no impact on the system, but eQuest requires each zone to have an associated system and thus you have to have it share a system with a conditioned zone).

Comment #2: Like Chris said, make a spreadsheet, and use it for every project. The small amount of time it takes to program excel to determine if the CFM is > or < than 20,000 CFM and automatically use the correct formula will pay for itself quickly.

Comment #3: Plain and simply state: eQuest's autosize routine is based on the 20 degree delta T that we have entered for each system (show a screenshot of that eQuest tab to help back this up, and circle in red). Therefore, although it is autosized, the CFM is correctly configured based on this 20 degree delta T, and thus specific entry of CFM quantities in the system tabs is not required.

James Hansen, PE, LEED AP

James Hansen's picture
Joined: 2011-09-30
Reputation: 200