For thousands of years clothing has provided the first line of defense against chilling temperatures and blazing sun rays, but history indicates that the idea of adding thermal layers to enhance the comfort of a shelter took a long time to develop. Initially, water-repelling, wind-blocking walls — found in caves or crafted from stone, wood or animal hides — sufficed as protection from the elements. But once people discovered a safe means of generating heat indoors, the motive to retain that warmth drove a desire to insulate their dwellings.
Instinctively looking to local resources, people discovered thermal properties in a broad range of natural materials. To create blanketing layers, they harvested or repurposed substances such as sod, cotton, paper, wood shavings, sawdust and more. Tapping into an ever-ready supply of cork native to their regions, people in southern Europe and Africa have used it to insulate their homes for many centuries. Ancient Greeks and Romans initially used locally mined asbestos to protect themselves from heat and thereby discovered the mineral’s insulating properties. (It was commonly used in modern structures until its health risks were established in the 1970s and ’80s.) And a lack of trees led Nebraska settlers to rely on an abundant supply of straw for their shelter, so they learned about the thermal advantages of straw-bale construction.
Another form of “bio-insulation” was harnessed in 1893 by Samuel Cabot, a chemist who started out making tarpaper and later became a famous wood-stain manufacturer. In an attempt to find a use for eelgrass (an overly prolific sea plant found along the Cape Cod coast), Cabot began researching and learned that some people stashed the dried weeds in their walls for warmth. After discovering that the plants’ air pockets offered thermal properties, he gathered, dried and sandwiched the grass between sheets of paper to make “Cabot’s Quilt,” which became one of his company’s major product lines for the next 40 years.
Two other materials (rock wool and slag wool) were predominant insulators from the mid-1800s to the mid-1900s. Made from fine strands of molten rock or industrial slag, both of these mineral wools are known for their fire resistance as well as their thermal protection. The 20th century brought the harnessing of a variety of new insulators. Finally recognizing the insulating potential of glass fibers (originally produced by ancient Egyptians for decorative pieces), glass makers and some manufacturers of asbestos and mineral-wool insulations (such as Johns Manville Inc.) expanded into production of fiberglass insulation during the mid-1900s. In 1944 Dow Chemical Co. patented Styrofoam, the forerunner of today’s extruded polystyrene foam, an increasingly popular insulator. And in the 1950s Thomas Jefferson’s idea to incorporate cellulose into his famous Monticello estate was resurrected when paper-base wool began to be mechanically produced and widely used as insulation.
Thanks to these developments, the growing prevalence of air conditioners and the energy consciousness that began in the 1970s and resurged with the green movement, insulation has evolved from a building amenity into a construction requirement. Modern homeowners no longer have to worry about devising ways to keep out the cold or keep in the heat; the only dilemmas we face are in choosing among the vast array of insulating products and approaches currently available and constantly emerging.