Completion date


Owner-occupied, 3 full-time occupants, typical residential occupancy.

Days per year Building is fully occupied:


Existing home. Air sealing, reduction of plug loads, replacement of propane-fired heating and hot water with electrical, addition of PV.

Type of Construction Retrofit
Number of buildings 1
Floor area of each building 1,200
Bedrooms 3
Bathrooms 1.0
Stories 2
Conditioned Building Volume 13,000 cu ft
Conditioned Floor Area 1,200 sq ft
Semiconditioned Floor Area 396 sq ft

Location and Climate Details

One side of residential duplex

120 Pulpit Hill Road
Amherst, MA 01002
United States
Location Type Suburaban
Climate Region Zone 5
Köppen Climate Type Dfb
Lat. / Long. POINT (-72.5236273 42.4174055)
Elevation 250 ft
Solar Insolation 3.57 kwh/m2/day
Annual CDD and Base Temp 214 | 70 deg F
Annual HDD and Base Temp 6,400 in 2012, 6,700 average | 65 deg F


Site conditions:
preexisting structure(s)
Site description:

Retrofit of existing duplex unit (one side of duplex only) within 32-unit cohousing community.

Materials and Design Strategy


It was a retrofit, with a minimum of new materials. The original construction in 1994 prioritized for sustainable and healthful materials, systems and design. Retrofit involved air sealing; a new, more efficient refrigerator; installation of HRV to replace exhaust-only ventilation; ASHPs to replace propane boiler; super-insulated water tank to back up existing solar hot water; installation of PV.

Special architectural measures:

The existing home was sun-tempered, well-insulated, and reasonably tightly built. The retrofit included targeted air sealing to improve performance. I think we need to go back and verify the air sealing, as I have reason to suspect that the mechanical installation may have resulted in breaches in the air barrier. (In spite of this, the home was net energy producing in the first year.)

LCA Description:


Indoor Environment Description:
Heat recovery ventilation replaced exhaust-only ventilation. The original materials were specified for indoor health, including white pine floors and cabinetry with water-based finish.