Baseline of existing building with major renovation

Mike Mentzos

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LEEDuser Basic Member

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December 30, 2024

According to ASHRAE 90.1-2010 Table G3.1.5 (f) for existing building envelopes, the baseline building design shall reflect existing conditions prior to any revisions that are part of the scope of work being evaluated.

Does this mean that for an existing building that concern a project that is major renovation the baseline envelope have to be constructed in conjunction with this paragraph of Table G3.1.5 (f) and not Table G3.1.5 (a) until Table G3.1.5 (e)

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

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Tue, 12/31/2024 - 16:55

Table G3.1.5 Baseline (f) obviates the application of G3.1.5 Baseline (a) and (b). Table G3.1.5 Baseline (c)(d)(e) still apply. Keep in mind that the renovation has to be from a similar building usage. For example you can't renovate an unheated warehouse and convert it to full conditioned offices. In that case G3.1.5 Baseline (a)(b) still apply.

Mike Mentzos

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LEEDuser Basic Member

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Tue, 12/31/2024 - 19:14

Marcus I would like to thank you and wish you happy new year But I am a litle confused My new question is why obviate only G3.1.5 Baseline (a) and (b) and not also (c) (d) and (e) as at "LEED REFERENCE GUIDE FOR BUILDING DESING AND CONSTRUCTION" page 354 I read (without exceptions):

For an existing building that was conditioned before major renovation and will be conditioned postrenovation, the
baseline building envelope should reflect the existing conditions, before the scope of work (Table G3.1-5 Baseline (f)).
However, for an existing building (or spaces in the building) that was previously unconditioned and is being renovated
to include conditioning, the baseline building envelope (or the envelope for any previously unconditioned spaces in the
building) must be modeled as if the building is new construction (i.e., according to Table 5.5).

So as my project concern an existing building that was conditioned ,why should follow the G3.1.5 Baseline (c)...for fenestration? And also i find these: Your (older) answer https://leeduser.buildinggreen.com/forum/existing-building-fenestration Thanks a lot

chris jordan

LEEDuser Basic Member

1 thumbs up

Mon, 05/04/2026 - 11:55

Yes, you’re reading it right, but missing the intent: for an existing building undergoing a major renovation, Appendix G requires the baseline envelope to reflect the pre-renovation existing conditions, specifically under Table G3.1.5(f), not the standard baseline assumptions in (a) through (e). Those earlier sections apply mainly to new construction or elements not covered by the existing condition rule. The whole point of Appendix G is to compare your proposed design against a defined baseline model, not an idealized upgrade scenario, so for renovations, the baseline must stay tied to what actually exists rather than current prescriptive values.