SS-J vs LS-C Report

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Hi all,

This is my first post on this forum, looking forward to learning a whole lot and eventually contributing. I've been reviewing energy models for about 4 months now, and I'm confused about the LS-C vs SS-J reports.

It seems that the LS-C report only considers the building loads related to infiltration, occupancy, lighting power and any other internal loads. Is this correct?

I see that the SS-J report provides a breakdown of the peak loads per system type. Does that mean it considers all things in LS-C in addition to outdoor air load? It seems this would be the way to size a buildings equipment. Last question: how can I sum all the system peak loads from SS-J without going line-item by line-item?

Ultimately, I'm looking to determine the % load reduction from a baseline model and a proposed model. The intention is for incentive purposes related to an improvement of the building envelope, and ERV's are not supposed to be considered. I would guess that the LS-C report would provide this load better than the SS-J, since ERV's consider outdoor air and further reduce the loads. 

Thanks all for your help. Cheers.


gregv97's picture
Joined: 2022-05-02
Reputation: 0

Hi Greg, 

This is a really good question - have you determined an answer?  You found the main difference in that SS-D or SS-J include the ventilation loads. I started to answer a while back, but I ran into a surprise result on a test. This was in the middle of purging as many spam users as possible from the forum and I forgot to circle back. HOWEVER, I am working on the same question again myself under a specific set of circumstances that require me to dig very deep. Specifically looking at LS-C vs SS-D - with the typical difference being that SS-D includes ventilation loads.

As far as your question 2 on exporting the loads, have you tried our load extractor?
Given you have paid for premium forum and asked a really good question, I have added full access to your account but no promises!
Check it out:

It extracts from the LS-B report and the SS-J report.

Just zip your .sim file and upload it (the zip file works a lot faster)

The tool is a text parser and sometimes doesn't work based on zone names, but it's pretty awesome and worked about 99% of the time in eQUEST 3.65.7173. We just updated much of the website core, so if it returns a file without an extension, just rename the file so it has extension .csv.

We have our own tool in python locally, but the online tool doesn't generate enough revenue for me to update it on our server (using PHP).

Anyway, I'll circle back based on my full findings of SS-D vs LS-C

Bob's picture
Joined: 2010-06-30
Reputation: 475

To make a fair comparison, I think it is better to compare LS-C or LS-D to SS-D because that shows the building loads.

The conventional answer to how they differ is "LS-C has no ventilation loads", and that often makes up the bulk of the difference.

However, the two reports are calculated differently and equipment sizing would be more appropriate using the SS-D (or SS-J). 

The LS-D Report Building Load

  • Based on steady state calculations (steady state meaning it assumes the whole building is operating at its design setpoints at the design hour and the hour before and so on)
  • Does not include ventilation
  • Does not account for building mass (because of steady state)

The SS-D report Building Load

  • Includes ventilation
  • Accounts for hourly changes based on the schedule. So if a building cooling setpoint was 85 over night and set to 75 the next morning at 8 am, there would be a load spike due to the rapid shift in temperature given the mass effects of the building
  • Includes heat transfer across interior walls, floors, and ceilings (so if an adjacent room is not at the design setpoint, then the heat transfer will be calculated based on the actual space temperatures for that hour)
  • Includes all loads seen by the coil such as fan heat, duct heat transfer, and even economizer effects.
The SS-J report gives the same information as SS-D but at the individual system level, where it shows a 24 hour profile of the peak day.

Bob's picture
Joined: 2010-06-30
Reputation: 475