Ventilation Load Opinions

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Dear All,

I?m attempting to quantify the difference between load sizing with DOE-2.2 and other proprietary software, and I?d like to hear others? opinions about method(s) to determine DOE-2.2 ventilation loads. The archives hold numerous discussions about this issue, but I see no definitive responses and some for which my own opinion differs (e.g. using reports that exclude latent loads). Here?s what I do for a block load approach, which is summarized with an example in the attachment:

1) Set up one multi-zone system for the building so that the LS and SV/SS reports are easy to cross-reference

2) Define the HDD and CDD, adjust design day schedules, settings/inputs, etc., as needed. The remaining steps assume all inputs are 100% accurate.

3) Run the simulation

4) Document the peak building loads from the LS-C report, both the Design Day and Standard Reports (internal and/or envelope loads only)

5) Document the peak system loads from the SS-J report, again for the Design Day and Standard Reports (system-level peak loads, including ventilation)

6) Take the worst-case differences between these reports, as illustrated in the attachment (Note: other reports provide the same maximums shown in the SS-J Standard Report, such as SS-I, SS-D, etc., but the SS-J provides both Design Day and Standard versions).

The issue that I see with this approach is that the LS-C and SS-J peaks do not necessarily occur at the same time, so to be technically accurate, one would need to use hourly reports to parse out envelope and internal loads for the hours corresponding to the SS-J peaks. The above would be an estimate, but I believe it to be about as close as one could get within the SIM file. I would appreciate any feedback or comments.



Dakota Kelley's picture
Joined: 2011-09-30
Reputation: 1

I use the same method. Sometimes LS-B is swapped with LS-C if I am trying to solve for the whole building.
I have backed out the calculations for a known amount of outside air and it was very close to being what one would expect for the OA load. It was 75 CFM at 96/77, which cooling to a dewpoint of 51 degF takes about 6.9 KBTU/H. The LS-B showed 12.73 KBTU/H and the space the unit served showed 19.82 KBTU/H in the SS-A report. The difference being 7.1 KBTU/H.

The issues you bring up about the peaks not occurring at the same time does seem to leave some error in the method, but this is as close to solving for ventilation load that I have figured out. Maybe someone else has a spot on approach, or there is a report that we are missing?

Also, this is solving for load not consumption. If one wanted to know the energy consumption due to the ventilation load that would be another task. Have you figured out a way to tackle this one?
Replace LS-B with data from LS-E and replace SS-J with data from SS-A, then factor in unit inefficiencies?

Joe Fleming

Fleming, Joe's picture
Joined: 2011-09-30
Reputation: 0

Thank you, Joe.

You are correct that this is for loads only; energy consumption is a separate issue that I have not yet tried to tackle. I?m also trying to stay away from the system sizing reports and look only at the peak building loads, or system loads since I?m defining a one-to-one relationship.

Thanks again,


Dakota Kelley's picture
Joined: 2011-09-30
Reputation: 1