Does every apartment need a programmable thermostat?

Every heating or cooling system in a dwelling unit needs a setback thermostat unless a central EMCS controls it. Gravity wall heaters, noncentral electric heaters, room air conditioners and some other types are exempt.

Are window and wall air conditioners exempt?

Room air conditioners and room air-conditioner heat pumps are exempt from the setback thermostat requirement in Section 110.2(c).

Does Title 24 require smart thermostats in apartments?

Not in dwelling units under 160.3(a)1, which asks for setback capability. Demand responsive thermostats are required for single-zone units in common use areas and when common-area equipment is replaced.

Who checks the controls?

The building department. Common-area controls are acceptance tested before occupancy, with a Certificate of Acceptance; dwelling-unit installations are documented on the Certificate of Installation.

Multifamily Temperature Control Under Title 24

Every heating or cooling system in a multifamily dwelling unit needs a setback thermostat that the resident can program for at least four periods a day, unless a central energy management control system controls it. That is Section 160.3(a)1, which points to 110.2(c). Systems serving common use areas need the fuller set of controls in 160.3(a)2.

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Where the rules sit

Multifamily buildings have their own subchapters of the Energy Code. Sections 160.0 to 160.9 hold the mandatory requirements, Section 170 the performance and prescriptive approaches, and Section 180 the rules for additions and alterations. Sections 160.1 to 160.9 apply to dwelling units and common use areas. Nonresidential spaces in a mixed-use building follow the nonresidential requirements instead.

Temperature control is in Section 160.3(a), and it splits in two: dwelling unit thermostats, and common use area controls.

Inside each dwelling unit

Section 160.3(a)1 is short. All heating or cooling systems, including heat pumps, not controlled by a central energy management control system (EMCS) must have a setback thermostat as specified in Section 110.2(c). That means a clock that lets the occupant program setpoints for at least four periods within 24 hours.

Exempt equipment: gravity gas wall heaters, gravity floor and room heaters, noncentral electric heaters, fireplaces and decorative gas appliances, wood stoves, room air conditioners and room air-conditioner heat pumps.
More than one unit in an apartment: one thermostat may control them all, or each may have its own. Separate units may also have an on/off control that overrides the thermostat.
Heat pumps with electric backup heat: the controls must keep the backup heater off when the heat pump alone can meet the load, and must cut the heat pump on and off at higher temperatures than the backup heat, under Section 110.2(b).
Variable or multi-speed equipment: the system and its thermostat together must modulate compressor speed with the load, and the installer certifies the tested control setup on the Certificate of Installation. That is Section 160.3(b)8.

Central systems serving the units

Where a central EMCS controls the dwelling units, 160.3(a)1 does not ask for a setback thermostat in each one: the EMCS takes that role. One exception points the other way. Systems that serve only dwelling units and shared living spaces, such as a common kitchen for units that lack their own, may follow the dwelling unit rule instead of the common area rules.

Common use areas

Corridors, lobbies, fitness rooms, central laundries and other common use areas follow Section 160.3(a)2.

Each zone has its own thermostatic control responding to the temperature in that zone. An EMCS may do the job.
Controls must reach down to 55°F for heating and up to 85°F for cooling, with a deadband of at least 5°F where one control handles both.
Each system can shut itself off when the space is not in use, by a time switch with a manual override of up to 4 hours, an occupancy sensor, or a manual 4-hour timer.
The system restarts to hold a setback heating setpoint and a setup cooling setpoint, except in mild climates where the code does not require them.
Single-zone air conditioners and heat pumps need thermostats meeting the demand responsive control requirements of Section 110.12, with exceptions for packaged terminal and room units.
Systems serving zones of more than 25,000 square feet combined are split into isolation areas that can be shut off separately.

Before an occupancy permit is granted, common-area controls are acceptance tested. Constant volume single zone air conditioner and heat pump controls, for example, are tested to Reference Nonresidential Appendix NA7.5.2, and a Certificate of Acceptance goes to the building department.

When equipment is replaced

The alteration rules in Section 180.2 carry the same requirements forward. An entirely new or complete replacement system serving a dwelling unit must meet 160.3(a)1, among other sections. In common use areas, when equipment such as an air handler, condensing unit or coil is replaced, an existing thermostat that does not meet the demand responsive requirements of 110.12 is replaced with one that does.

For what else a replacement brings into scope, such as duct sealing and verification, see multi-family HVAC and Title 24. For the forms a building uses by height, see low-rise and mid-rise multifamily. Multi-family reports start from $345, with unlimited revisions until you comply.