Deep Energy Retrofits for Multifamily Buildings

What it is

A standard retrofit replaces one system. A deep retrofit changes how the whole building uses energy. It reduces the load first, through envelope and ventilation work, then sizes new, usually all-electric equipment to the smaller load.

The result is a building that needs less energy to stay comfortable, not just newer equipment.

Typical measures

Measures commonly combined in a multifamily deep retrofit
Area	Measures
Envelope	Wall and attic insulation, air sealing, window replacement, cool or insulated roofs
Heating and cooling	Heat pumps replacing furnaces, boilers for space heat, and old AC
Ventilation	Balanced or heat-recovery ventilation once the building is tighter
Lighting and controls	LED lighting, central controls, metering and submetering
On-site power	Solar and, where it fits, battery storage

For the heating and cooling piece, see heat pump HVAC retrofits.

One project or phased

Single project

All measures in one contract, often during a major renovation, recapitalization or vacancy. One mobilization and one design, but a larger upfront commitment.

Phased

Measures timed to equipment end of life, unit turns and roof cycles, under one long-term plan. Smaller steps, but each phase must leave room for the next.

Either way, write the full roadmap first. A heat pump sized before envelope work may end up larger than the building needs.

Occupied-building logistics

Do exterior and roof work first, where residents are least affected.
Schedule in-unit work in blocks, with notice and a clear day-by-day plan.
Decide early whether any work needs temporary relocation, and who arranges it.
Keep heating and cooling running, or provide temporary units, during changeover.
Name one point of contact for residents for the whole project.

Funding

Deep retrofits are usually paid for with a mix of capital reserves, refinancing proceeds and any incentives or technical assistance that is open at the time. California's regional energy networks and income-qualified programs have supported whole-building work. Check the California multifamily program directory for current status.

Benchmarking data helps make the case for funding. See California energy benchmarking. Affordable housing operators can also start from a capital needs assessment: see affordable housing retrofits.

Outcomes and past projects

Results depend on the building and the measures. Ask any contractor for comparable past projects: building type and size, measures installed, how residents were handled, and before-and-after utility data where available.

Questions before you begin

What makes a retrofit "deep"?

A deep energy retrofit treats the building as a system and combines several measures, usually envelope, heating and cooling, ventilation and controls, instead of replacing one piece of equipment. The goal is a much larger cut in energy use than any single measure would give.

Is a deep retrofit done all at once?

It can be, often during a major renovation or refinancing. Many owners phase it instead, lining each step up with equipment end of life, unit turns or roof replacement.

Can residents stay during a deep retrofit?

Often, yes, especially when work is phased and mostly exterior. Some interior work may need short-term relocation. The resident plan should be part of the scope from the start.

How is a deep retrofit funded?

Usually a mix: capital reserves, refinancing, and any program incentives or technical assistance that is open for the property. Program terms change, so confirm each one before budgeting.

Deep Energy Retrofits for California Multifamily Buildings