Built in 1916, the 1,500 square foot Concord Four Square retrofit features an upgraded mechanical system as well as a super-insulated and airtight enclosure. Closed cell spray foam insulation installed to the interior of the foundation wall and the underside of the roof deck increases the home’s airtightness while providing a component of the high performance thermal enclosure. Cavity insulation, rigid foam insulation on the walls, roof and under the new basement slab and high performance windows complete the thermal enclosure. Water management details developed for the windows, now set into 4 inches of rigid foam insulation, and a ventilation space provided behind the cladding increase the home’s durability. New heating, cooling and hot water equipment as well as an entirely new ventilation system combine with the insulated and airtight enclosure to achieve a 66% reduction in energy use when compared to a 2008 code built home.