In a previous article, I discussed “home performance,” the practice of improving the energy efficiency of existing homes by applying the principles of building science, a data-driven approach to energy improvements. Home-performance contractors test each house using sophisticated equipment, analyze the data, and only then make recommendations as to which solutions are right for the house.
Air sealing the home is usually the top priority because most homes are leaky. The benefits from tightening a house’s shell are numerous: reduced energy use, comfort, better health, and lower utility bills.
Controlling indoor temperature is often the second priority — and that means insulation. Because of our mild climate, insulation only started being routinely installed in the late 1970s, when California changed its building codes to require it. Although a positive development, the amount of insulation required back then was insufficient. Furthermore, the industry didn’t have the scientific understanding of how insulation really worked, so its installation often led to other problems, such as mold or wood rot.