Project Team

Ratings, Awards and Recognition


Mass CEC tier 3 rebate
HERS Five Star Plus+ Certificate

HERS Index::

This is a new house in the Katywil Farm Community, an intentional cohousing community in Colrain Massachusetts. It was designed as a Net-Zero house by the owner/architect Peter Brooks after taking Marc Rosenbaum's first NetZero design course. It is derived from the Capstone project from that course.  The house was built by Karsten Construction of Leverett. We have a heated walk-out basement that is unfinished but has a radiant slab floor and an unheated root cellar room. The house is a 26 x 34' rectangle with a secound floor that has shed dormers on the North and South sides. The house is sited facing slightly East of South on a South facing slope. It is designed with about 8% south facing triple glazed windows and small windows on the north. The walls are double studded 12" thick packed with dense cellulose. The roof was designed to have 18" of cellulose, about R60. The house was built quite tightly and tested at .8 ACH50. The house is ventilated by a Fantech Flex 100 ERV. The house is heated by a Daikin air to water heat pump that pumps hot water to the DWH indirect tank and the radiant slab and radiators. There is a 7.6 kW solar PV array of 30 panels, with half on the 45 degree sloped roof and half of the panels are on the top of the dormer roof at about 30 degrees.

 We have just received 12 full months of energy data and we seem to have generated enough power to be within 12% of NetZero. We need to generate an extra 671 kWh to offset the 24 gallons of propane that we used for cooking. We will add a monitoring to the system and refine our use until we meet our goal of Net-Zero. 



Quick Facts


Location Colrain, Massachusetts
Building Type Single family residence
Project Type Zero Energy Ready / Near Zero Energy
Basis of Performance Claim Modeled, Verified
Bedrooms 2
Bathrooms 2.0
Conditioned Floor Area 2,200 sq ft
Total Cost of Project $480,000

Energy Summary

Energy Data Type Modeled, Verified
Renewable Energy System Type(s) Photovoltaics

Mass CEC tier 3 rebate
HERS Five Star Plus+ Certificate

HERS Index 5
Net electricity usage (purchased) 1,262 kWh/year
Natural gas amount (purchased) 671 kWh/year
Annual renewable energy generated 9,987 kWh/year

Envelope and Mechanicals

Subslab assembly

We have two layers of 2" extruded polyurethane under the slab, R20,with a vaor barrier and 6" of crushed stone.

Foundation wall assembly

The below grade foundation is an 8" concrete wall with waterproofing. It is insulated on the inside with 2" of polyurethane insulation and a stud wall with blown in dense packed cellulose and 1/2" gypsum board for a total nominal R value of 22.

Above grade wall assembly

The above grade walls are 12" double studded walls with dense packed cellulose between zip sheathing and 1/2" gypsum board. The band joist is sprayed with 8" of closed cell foam. The air and water barriers are taped zip sheathing.

Door Assembly

Fiberglass with wood edges, Therma-tru, smoothstar.