The great thing about the exterior of the house was that we were able to retrofit the envelope to a higher energy efficiency, technically called a 'deep-energy retrofit,'" says architect David Pill. The exterior galvanized steel, from MBCI, and the fiber-cement siding, by Certainteed, are low maintenance and make the dated 1970s wood exterior a thing of the pastThe great thing about the exterior of the house was that we were able to retrofit the envelope to a higher energy efficiency, technically called a 'deep-energy retrofit,'" says architect David Pill. The exterior galvanized steel, from MBCI, and the fiber-cement siding, by Certainteed, are low maintenance and make the dated 1970s wood exterior a thing of the past