The talk at an annual building conference in Boston is about how to reduce energy use in houses by more than 50 percent. Early pilot tests show it can be done, but with steep costs.

BY MARCH 12, 2010 6:07 AM PST

BOSTON–Perhaps not surprisingly, wrapping a home in an air-tight seal and adding insulation dramatically lowers utility bills. But the question is: can people afford it?

On Thursday, contractors who could be considered pioneers in “deep-energy retrofits” presented results from their projects at the Northeast Sustainable Energy Association’s BuildingEnergy conference here. In general, the data from early projects in Massachusetts shows that these energy makeovers delivered big gains in efficiency–on the order of 50 percent to 70 percent.

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 (