There are a number of techniques to cut building energy but the one these contractors often focus on is superinsulating, or sealing the building "envelope" and adding insulation, both inside and on the exterior of buildings.In one multiphase project in western Massachusetts, the homeowners anticipate getting a 70 percent reduction in energy use by adding a layer of foam insulation on the roof and outside walls among other enhancements. Slashing energy use means lots of insulation: the roof will have an R-value, or insulating value, of 59, which is two or three times that of a typical New England home.Closer to Boston, a superinsulation project at an 85-year-old, two-family home in Arlington, Mass, was able to reduce the amount of heating oil by about two-thirds in its first year, according to homeowner Alex Cheimets In that case, homeowners decided to seal and add insulation to the exterior of the home when they had to replace the aging shingles.