This retrofit house is located in Newton, MA (Cold Climate). It involved adding two layers of 2” foil-faced polyisocyanurate rigid insulation above the roof deck with 2x4 furring above the insulation to vent the roof, while the existing rafter bays filled with existing fiberglass insulation were encapsulated with open-cell spray foam insulation. The walls were retrofitted to add two 2” layers of foil-faced polyisocyanurate rigid insulation to the exterior of the wall sheathing and dense pack cellulose insulation in the framing cavities. The windows were replaced with new triple- and double-glazed windows and open-cell spray foam insulation was added at the mud sill. Closed-cell spray foam insulation was added to the interior of the foundation wall and a new slab was cast with 2” XPS rigid insulation under slab.
For complete details on this deep energy retrofit project, go to
National Grid Deep Energy Retrofit Pilot Project–Cape Basement Renovation Turned Comprehensive DER