Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question

Baseline Lighting Schedule Adjustment for ASHRAE 90.1-2016, 2019 and 2022 Appendix G

asked 2024-05-20 23:16:35 -0500

Keigo's avatar

updated 2024-05-25 07:06:42 -0500

A question about how to interpret ASHRAE 90.1-2016, 2019 and 2022 Appendix G.

According to Table G3.1, lighting shcedules in employee lunch and break rooms, conference/meeting rooms and classrooms in the Baseline case shall be reduced to reflect occupancy sensors.

image description

(In the first place, I don't understand why the Table doesn't use exaxtly the same wordings as Space Types in Table G3.7.)

I tried to find the closest Space Types in Table G3.7 to employee lunch and break rooms, conference/meeting rooms and classrooms, but none of them has Occupancy Sensor Reduction. How should I interpret this? No errata on this requirement has been issued.

image description

The Baseline case shall have occupancy sensors in breakrooms, conference rooms and classrooms, but the occupancy sensor reduction is 0%. So, there is no need to reduce the lighting schedules in the Baseline case due to occupancy sensors. Am I correct?

edit retag flag offensive close merge delete

2 Answers

Sort by ยป oldest newest most voted

answered 2024-05-24 09:56:08 -0500

Hi @Keigo. Not sure I'm entirely answering your questions, but here's my take. I haven't sifted through past 90.1 interpretation requests - may do that at some other point. And the 2019 User Manual (which I haven't consulted) may be useful here.

I do agree that the language is confusing for baseline building design (BBD) lighting schedules, when altered to reflect automatic shutoff controls / occupancy sensors. IMHO, the requirement is poorly worded, and should instead read something like (90.1 2022, SI edition):

In buildings > 500 m2, lighting shall be modeled having automatic shutoff controls (e.g. occupancy sensors) in:

  • employee lunch and break rooms
  • conference/meeting rooms
  • (certain) classrooms (e.g. college/university)

First, interior lighting controls apply (well) to spaces - not buildings. So I think the scope of the requirement needs rewording. Second, there are many instances in 90.1 where occupancy sensors are explicitly referenced (even mandatory). Yet elsewhere in 90.1, the more general term automatic shutoff control device is retained. I'd consider an occupancy sensor as an obvious automatic shutoff control device. Other automatic shutoff control options would include key-card access, logging out of one's designated (enclosed) office workstation, etc. describes automatic shutoff controls (no explicit mention of occupancy sensors, BTW). These are mandatory for a dozen or so space types (see "auto full OFF" column in Table, including the 3 listed above ("lounge" should be associated to "break rooms", BTW). I believe the intention of this requirement is to ensure that some of these space types (not all), required to have mandatory automatic shutoff controls, be modelled accordingly. Why just these 3? Can't say for sure, but they do share common characteristics:

  • larger (in m2) than the others
  • when occupied, populations typically vary from half-a-dozen to 30 or 40 people - not single occupancy
  • their use tends to be somewhat predictable (e.g. number of expected people, expected/planned events).

Occupancy in the other (smaller) targeted space types (like enclosed offices, supply/storage rooms) are much more challenging to predict. So my take is that the 90.1 TC is making here a reasonable judgement call on when/where to factor in mandatory automatic shutoff controls when working with Appendix G. Hence the "NONE" entries in G3.7. Why "None" in some cases and "0%" reduction elsewhere in G3.7 - beats me! And why suggest a 30% reduction for enclosed offices (G3.7), when these spaces are already required to integrate automatic shutoff lighting controls as per Table Double-dipping? Can't answer ...

Regardless, the very same schedule alterations should equally apply IMO to the proposed building design (PBD) schedules, which I think is what is described (loosely) in (g):

For lighting controls, at a minimum, the PD shall contain the mandatory automatic lighting controls specified in Section 9.4.1 (e.g., automatic daylight responsive controls, occupancy sensors, programmable controls, etc.).

In (i), it ... (more)

edit flag offensive delete link more


Thank you so much for taking time to answer my question. So, Occupancy Sensor Reduction in Table G3.7 is the reduction for the Proposed case compared to the Baseline case, not the reduction compared to the default lighting schedule. None means that both the Proposed case and the Baseline case shall have automatic shutoff controls by occupancy sensor as a mandatory provision.

Sounds reasonable.

Keigo's avatar Keigo  ( 2024-05-24 22:41:55 -0500 )edit

answered 2024-05-24 23:00:19 -0500

Keigo's avatar

updated 2024-05-25 02:35:36 -0500

I just want to attach an image in response to @Denis Bourgeois 's answer.

In summary (my take): 90.1 App. G requires factoring the impact of automatic lighting shutoff controls (re: 3 listed space types) in buildings > 500 m2:

  • by altering (in some reasonable way) typical lighting schedules in the BBD

  • the same altered schedules equally apply to the corresponding 3 space types in the PBD

I think I found the reasonable way in ASHRAE 90.1 User's Manual (2016 and 2019 versions): 10% Reduction.

image description


The above may be wrong. The user's manual continues as follows (see blue lines). image description

It suggests that automatic shutoff controls (= automatic time-based shutoff controls) and occupancy sensors are different things. The Baseline lighting schedule for the 3 space types should be adjusted using Occupancy Sensor Reduction in Table G3.7, which brings me back to my original question. I got stuck. It's possible that the ASHRAE 90.1 User's Manual is incorrect, but I can't judge for now.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Training Workshops


Question Tools

1 follower


Asked: 2024-05-20 23:16:35 -0500

Seen: 170 times

Last updated: May 25