Insulated siding can improve a home’s energy efficiency. Most exterior walls have insulation in between the wall studs, but allow significant energy loss through the studs themselves. Wall studs, both wood and metal, are poor insulators — when they come in contact with the exterior cladding, they allow heat to pass through them (which is called a thermal bridge). Since these studs represent up to 25 percent of the wall surface of an average home, it’s like having an entire exterior wall with no insulation at all.