November 18, 2025

An All-Electric, Prefabricated Home Built for Urban Living: A Case Study

Unity Varm Exterior in Urban Residential Neighborhood

A Rebuild That Redefined What Their Home Could Be

Cynthia and Tim wanted a home that felt comfortable, healthy, and efficient without giving up the convenience of their Somerville neighborhood. After weighing the idea of a deep energy retrofit, they chose a fresh start: a new, prefabricated, all-electric home built with Bensonwood’s high-performance panelized system. The result is a quiet, sun-filled space that met Mass Save’s Tier Two energy efficiency program standards at that time, and earned the couple a $25,000 incentive.

Why a Deep Retrofit Wasn’t Enough

Located on an urban lot close to the metro, the existing mid-century home offered convenience – but lacked comfort and energy efficiency.

“Our original plan was to renovate,” said Tim in a recent interview. “But it was quite old and a pretty poor quality home and we ended up getting to the point where it would have been cost prohibitive to renovate and we still wouldn’t have gotten what we wanted in terms of the quality of the house and the way we want to live in it.”

While weighing the option of renovating versus starting fresh, Tim and Cynthia came across Bensonwood – Unity Homes at that time. At first, they were skeptical. Could offsite construction be a possibility for their lot with their tiny street and thick traffic? Once they connected with our team to find out, they found that panelization is actually a very good solution for city lots with reduced onsite labor requirements, faster dry-in and less site disturbance.

The lot was ideal for a fast, efficient building process that would minimize noise and traffic while delivering exceptional performance results. And, by building new, they were able to create a home from the ground up that aligned with their priorities: a full-height basement, a fully electric mechanical system, high-performance windows, and a tightly built enclosure designed for long-term efficiency.

“One of the most exciting things was seeing it go up,” said Tim. “Monday morning there was a hole in the ground and by Thursday I could walk up to the second floor.”

All-Electric Living in a Unity Varm

Tim and Cynthia were drawn to the Varm because they wanted a floor plan that gave them the maximum amount of usable space but with the smallest footprint.

“The Varm being a nice rectangle with two full stories allowed us to meet that objective,” said Tim. “Having that sort of simple modern farmhouse aesthetic with the gable end style fit really well with the neighborhood so it doesn’t look out of place.”

Like many homeowners exploring a pre-engineered platform, Tim and Cynthia initially wondered whether starting with an existing plan might feel restrictive.

Instead, they found that the structure provided clarity and offered a strong foundation while still allowing them to shape the home around their lifestyle and priorities.

“We were a little bit anxious at the beginning thinking that having some designs as a starting point would be limiting in terms of being able to be really creative with how you put the house together…we actually found that it was liberating because if you start with just a big blank sheet of paper that’s actually almost harder,” said Tim.

The Värm’s simple form supports exceptional insulation and airtightness, helping keep operating costs low. With solar panels now installed, their only major utility expense is electricity-an outcome they describe as surprisingly affordable.

In fact, the solar array has produced far more electricity than the homeowners consume, earning them a surplus credit with Eversource in just over a year. Even better, Cynthia and Tim chose to share their success by donating their excess energy credits to the Somerville Homeless Coalition, helping offset electricity costs for those in need. Through Eversource’s program, surplus credits can be banked or transferred to another account—an opportunity these generous homeowners were proud to embrace.

The High-Performance Details Behind the Design

Certifications
- U.S. Environmental Protection Agency (EPA)
- EPA Indoor airPLUS.
- U.S. Department of Energy Zero Energy Ready Home.
- EPA WaterSense.

Building Envelope
- Infiltration: Blower door test achieved at impressive 0.63 ACH50.
- Attic: Air Sealed and insulated with loose-fill cellulose (R-60).
- Walls: 9.5” prefabricated exterior walls wooden I-Beams with OSB on both exterior and interior layers plus dense-packed cellulose (R-35).
- Windows: Triple-paned, double-gasketed with .16 U-factor and .38 Solar Heat Gain Coefficient (SHGC).
- Foundation: Standard poured concrete walls: Rigid foam board (R-15).

HVAC
- Mitsubishi non-ducted 11.0 Heating Seasonal Performance Factor (HSPF) and 18 Seasonal Energy Efficiency Rating (SEER) air-to-air heat pump provides heating and cooling for bedrooms and bathrooms.
- Airia Brands Lifebreath Heat Recovery Ventilator system (72 CFM/35 watts) supplies fresh, balanced, filtered air to the living space 24 hours per day.

Hot Water
- Bradford White 50-Gallon heat pump hot water heater (3.44 UEF).

Solar and EV Charging
- 7.2 kW solar array was installed on the roof to satisfy all of the home’s electric needs. The system frequently generates twice its current load, so it is better than Net Zero.
- Electric vehicle charging station ready – the owners currently have electric bikes instead.
- Annual Electric savings: $5,694.