Deep Energy Retrofit Case Study

The Carol Avenue Apartments in Boston are undergoing a deep energy retrofit scheduled for completion in late 2024. The project focuses on transitioning a 33-unit, 1910-era property from fossil fuel-based systems to a fully electric infrastructure. By combining interior wall insulation, roof upgrades, and the installation of a Variable Refrigerant Flow (VRF) system, the property is estimated to reduce energy use by 55 percent. The addition of 65.3 kW of rooftop solar PV is projected to further increase total energy reduction to 64 percent and reduce greenhouse gas emissions by 41 percent.

• The deep energy retrofit, consisting of envelope improvements and electrification, is estimated to reduce energy use by 55 percent, lowering the Energy Use Intensity (EUI) from 80 kBtu/sf to 36 kBtu/sf.
• The integration of rooftop solar PV systems totaling 65.3 kW (split into 22.6 kW and 42.7 kW systems) is projected to serve 19 percent of the total load, increasing the total energy reduction to 64 percent and the greenhouse gas emissions reduction to 41 percent.
• To preserve the historic brick façade, the building envelope strategy focuses on interior upgrades, increasing wall thermal resistance from R-5 to R-12 using 1.5-inch mineral wool board and raising roof thermal resistance to R-65 with blown-in fiberglass and polyiso insulation.
• The property is transitioning to a fully electric site by replacing gas-fired heating and hot water with a centralized all-electric Variable Refrigerant Flow (VRF) system and electric resistance water heaters.
• The anticipated hard construction cost for the deep energy retrofit scope (envelope and mechanical) is $5,163,410, which equates to $148 per square foot of floor area or $156,467 per apartment.

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} }