Perhaps the most eco-friendly feature of the project is architect Mike Shively's preservation of the original structure. "I always believe in starting a project by identifying the best parts of what you have," he explains. "In this case [it was] the solid masonry construction and timber floor structure. I fired out all the perimeter walls and used spray foam insulation and Marvin windows to get a tight seal that keeps my heating and cooling costs low."  Photo 1 of 8 in A Chicago Renovation Taps Into its Attic to Almost Double its Square Footage