Deep Energy Retrofit Case Study

This case study details a deep energy retrofit of the Carol Avenue Apartments in Boston, a 33-unit affordable housing property built in 1910. The project, scheduled for completion in late 2024, focuses on eliminating on-site fossil fuel combustion through electrification, improving the building envelope from the interior to preserve a historic brick façade, and installing rooftop solar PV systems.

• The retrofit is projected to reduce energy use by 55 percent through electrification and envelope improvements, lowering the Energy Use Intensity (EUI) from 80 kBtu/sf to 36 kBtu/sf. When including a 65.3 kW solar PV system, the total energy reduction is anticipated to reach 64 percent, with a modeled EUI of 29 kBtu/sf.
• Greenhouse gas (GHG) emissions are expected to decrease by 26 percent through energy efficiency and electrification alone. With the addition of on-site solar, the total anticipated GHG emissions reduction is 41 percent, assuming Renewable Energy Credits (RECs) are not sold to third parties.
• To preserve the historic brick façade and comply with zoning restrictions, envelope upgrades are being performed from the interior. This includes installing 1.5-inch mineral wool board and gypsum board on exterior-facing walls to increase thermal resistance from R-5 to R-12, and adding blown-in fiberglass and polyiso insulation to roofs to reach R-65.
• The project replaces gas-fired heating and hot water with an all-electric centralized Variable Refrigerant Flow (VRF) cassette system for heating and cooling. While domestic hot water is currently transitioning to electric resistance heaters, there are future plans to install heat pump water heaters.
• Based on January 2023 preliminary estimates, the hard construction cost for the deep energy retrofit scope (mechanical and envelope) is $5,163,410, which equates to $148 per square foot or $156,467 per apartment. The insulated envelope assembly alone costs $1,429,800, and additional tenant relocation costs are estimated at $908,000.

APA

RMI (n.d.). Deep Energy Retrofit Case Study. https://rmi.org/app/uploads/2023/11/carol_ave_case_study.pdf

Chicago

RMI. Deep Energy Retrofit Case Study. n.d. https://rmi.org/app/uploads/2023/11/carol_ave_case_study.pdf.

Wikipedia

{{cite report |author=RMI |title=Deep Energy Retrofit Case Study |url=https://rmi.org/app/uploads/2023/11/carol_ave_case_study.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{rminddeep, author = {{RMI}}, title = {{Deep Energy Retrofit Case Study}}, institution = {RMI}, url = {https://rmi.org/app/uploads/2023/11/carol_ave_case_study.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }