If you live in an older home in New England, chances are your exterior walls looks like the example on the left: no insulation, questionable vapor barrier, plenty of gaps to allow transfer of air between interior and exterior. Even if you don’t have X-ray vision, your heating and cooling bills will give you some clues as to the state of your building envelope. An energy analysis will show specific problem areas but if your home is already on an old lot which won’t accommodate new construction, a Deep Energy Retrofit (DER) may be your best option.
This approach essentially wraps the existing building in a blanket of insulation. The image on the right shows fiber insulation packed into the existing wall framing as well as a new interior wall which houses electrical boxes and other penetrations which reduce the insulation depth at their locations. Foil backed rigid foam insulation has been added to the exterior out to the depth of the roof overhang for the dual benefit of increasing insulation value and providing a continuous air barrier. All joints between materials are carefully sealed and gaps are filled with expanding foam.
This cutaway model is on view at booth 1010 at the NESEA Building Energy 12 conference in Boston through March 8. Exhibitors are Passive House New England and member representatives from Zero Energy Design and Boston Green Building.