Adaptive Reuse and Title 24
When an office or commercial building is converted to apartments, the Energy Code applies the multifamily alteration rules of Section 180.2 to the building's new occupancy, not the nonresidential rules it was built under. Only what the conversion changes is regulated, and space that was never heated or cooled becomes an addition.
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The new occupancy decides
Part 6 follows a converted building into its new use. Section 100.0(e)3 says that for alterations which change a building's occupancy classification, the additions-and-alterations section for the occupancy after the alterations applies, which for housing is Section 180.0. Section 180.2 confirms it, covering alterations made in conjunction with a change in building occupancy to a multifamily occupancy. An office building converted to apartments is read against the multifamily chapter, not the nonresidential Section 141.0 it was built to. Converting to hotel rooms is different, because hotels and motels stay under Section 141.0.
Multifamily has its Section 100.1 meaning: a Group R-2 building other than a hotel, motel or timeshare, a Group R-4 building, or a nontransient congregate R-3 residence. Conversions the other way, into a commercial use, are on change of use and Title 24.
A change of occupancy alone does nothing
The Multifamily Compliance Manual is direct about it: a change of occupancy without any alterations requires no action under the Energy Code. The work is the trigger. Conversions to housing seldom stop at a change of use, because dwelling units need kitchens, bathrooms, ventilation, water heating and their own heating or cooling, and each of those is a regulated system.
What the alteration rules ask
Only what changes is regulated. On the prescriptive path of Section 180.2(b), each altered component and any new equipment serving it must meet the listed mandatory sections and the alteration requirements; untouched components need not comply. On the performance path of Section 180.2(c), an altered component's standard design is the more efficient of its existing condition and the Section 180.2(b) value, and unaltered components are modelled identically in both designs. A typical office-to-housing scope reaches:
- Windows: replacements meet Table 180.2-B, explained on apartment window replacement.
- Ventilation: an entirely new dwelling-unit ventilation system meets Section 160.2(b)2 under Section 180.2(b)5A, and no dwelling-unit air leakage test is required for alterations.
- Lighting: lighting in the new units meets Section 160.5(a), and common areas whose lighting is installed for the first time meet the new-construction rules, under Section 180.2(b)4.
Section 180.4 also lets any addition or alteration comply by meeting the requirements for the entire building.
Where a conversion becomes an addition
Space that was never heated or cooled, such as a warehouse bay or an enclosed parking level, becomes newly conditioned space when it is converted, and Section 100.1 treats that as an addition under Section 180.1. New dwelling units created that way need whole-dwelling ventilation airflow based on their own floor area. Exception 6 to Section 180.1 removes the PV and battery requirements of Sections 170.2(f) to (h) from additions, and the manual lists them as not applicable to alterations.
Mixed use and story count
Where shops stay on the ground floor, Section 100.0(f) applies each occupancy's rules to its own space. If one occupancy is at least 80 per cent of the conditioned floor area, Exception 1 lets the envelope, HVAC and water heating follow that occupancy, with lighting still met space by space. The number of habitable stories then sets the forms, LMCC up to three and NRCC from four, as explained on low-rise vs high-rise multifamily.
Common Title 24 Questions
- Do apartments need Title 24?
- Does a duplex need Title 24?
- Do triplexes and fourplexes need Title 24?
- Which Title 24 forms does a multi-family project use?
- What is an LMCC certificate?
- How much does a multi-family Title 24 report cost?
Frequently Asked Questions
No. A newly constructed building is one never used or occupied for any purpose. Altering existing conditioned space is an alteration under Section 180.2; converting space that was never conditioned is an addition under Section 180.1.
No. Only the altered components and the new equipment serving them must comply. Section 180.4 offers whole-building compliance as an option, not a requirement.
Not under Part 6. Exception 6 to Section 180.1 removes the PV and battery requirements from additions, and the Multifamily Compliance Manual lists them as not applicable to alterations.
The multifamily set: LMCC certificates for buildings of up to three habitable stories and NRCC certificates for four or more, as listed in Table 2-2 of the Multifamily Compliance Manual.