The Francis Cabot Lowell Mill I & II


The Francis Cabot Lowell Mill I & II is a 258-unit elderly/disabled residential apartment complex housed in what was the first fully-automated mill building in the country. Built in 1813, it was converted to apartments in 1978-79. It is listed on the National Historic Register as a Historic Site Building, and is part of a municipal riverwalk and complex that houses the Charles River Museum of Industry & Innovation.

After 37 years as an apartment building, the heating and DWH boiler systems were in need of replacement. The key challenge was determining the best possible system to replace the boilers and how to convert them while maintaining heat and hot water for residents.



The property applied to and was accepted as a Low-Income Energy Affordability Network (LEAN) project. The LEAN program is designed to help low- to moderate-income developments improve energy savings by offering equipment, lamps, and fixtures free of charge to qualifying properties. 


Action Energy Services, an energy efficiency contracting program that partners with LEAN, designed a high-efficiency gas fired boiler and indirect water heater system for the property which features multiple boilers with thermal efficiency rating of 92% or greater. In addition to the boiler upgrades the LEAN program assisted in the conversion of all the common area lighting from recently converted T8 fluorescents to LED lamps.

The project started at the end of the heating season in June 2017 so as not to disrupt the comfort of tenants. The heating equipment was removed from the boiler rooms and the hot water was swapped from the old system to the new one in a single day, thus limiting disruption of hot water. 



In addition to the common area lighting upgrades, the LEAN program worked with the building owner to upgrade the apartment unit lighting to LEDs as well. This provided a direct benefit to the tenants since they are responsible for their in-unit electric bills, thus they saved money.


Annual Energy Use

(Source EUI)
Baseline (2016)
93 kBtu/sq. ft.
Expected (2018)
79 kBtu/sq. ft.

Energy Savings:


Annual Energy Cost

Baseline (2016)
Expected (2018)

Cost Savings:


Sector Type



Waltham, Massachusetts

Project Size

250,000 Square Feet

The Francis Cabot Lowell Mill I & II
The Francis Cabot Lowell Mill I & II