Granite walls, marble floors, and heavy timbers, that’s the way to build a sustainable house – or it was for palaces and castles. While that may look sustainable (go check some ruins that are mostly rubble) there are newer measures of sustainability: economic and environmental. The materials we use to build our houses are evolving.
Go further back to the days of caves. That was sustainable living! It was also limiting. There are only so many caves around. Step forward in history and it can sound like the story of the three little pigs: straw, sticks, and bricks. Each is sustainable in its own way, as long as the big bad wolf doesn’t drop by for two of them. Our more modern materials have typically been wood, glass, concrete, and steel. Mix and recombine as necessary to create a variety of styles from log cabin to contemporary Modern.
Wood is the traditional building material for much of the world. It is hard to invent something that is as readily available, light, cheap, pleasing, and easy to shape as wood. Almost every surface could be made from trees: walls, floors, doors, and ceiling. Wood has evolved from chopping down whichever tree was closest, to using the right tree for the right project. Like any organic material, the key to making wood construction sustainable is sustainable harvesting. Turn wood into a composite with the right adhesives and create plywoods and laminated beams that are stronger and more resilient. Wood can live longer as lumber than as a tree. It can also be reused as weathered wood in new buildings.
Glass is at the other extreme because it is a completely inorganic material. Scoop up the right kind of sand, add the right “impurities”, melt it, cool it, cut it, and install it. Sand is created by the natural process of erosion occurring around the planet. We’re not likely to run out soon. The greatest non-renewable cost is the energy required to melt the broken shells and rocks that become sand. As we develop more efficient renewable energy sources, this concern shrinks. Waste materials can be recycled, driving down the cradle-to-grave costs. Coatings, laminates, and the addition of other chemicals makes each pane lighter, more durable, and more energy efficient in production and in the home.
Concrete is so ubiquitous that it can be hard to remember that we invented it about 9,000 years ago, before we understood chemistry. Roman aqueducts continue to carry water even though they’ve been exposed to the weather for thousands of years. It is like building with liquid stone. Unfortunately, treating the lime, and creating concrete releases significant quantities of greenhouse gases. It is heavy, too, which makes it financially and environmentally expensive to transport. It is now being recognized for sustainability thanks to its longevity, weather protection, and as an aid in thermal regulation. Somewhat like glass, concrete can be broken up, mixed with new, and used again. Fortunately, ways to make concrete mix are in development that will either reduce, eliminate, or even reverse the greenhouse gas impact.
Steel is increasingly popular. It has the benefits of being lightweight for its strength and is relatively easy to shape. The waste is easy to reuse, too. The added bonus is protection against pests. Like sand, it has the high energy cost of melting rocks. Steel has evolved more from the way we use than from the way we make it. Structural elements are increasingly steel rather than wood. Exposed I-beams are accepted as architectural elements. Steel studs for walls are saving weight and trees while also making it easier for plumbers and electricians to route pipes and wires thanks to pre-cut holes. Protection from rust is a concern, which ironically can be provided by metal roofing. Corrugated panels work inside and out, and have graduated from siding and roofing for sheds to functional ornamentation for houses. Like sand, it can be reused and recycled further decreasing the systemic life cycle cost.
Extending conventional materials for sustainability takes a lesson from reinforced concrete where steel rods that are good in tension work with concrete that is good in compression to create structures that use far less material.
The most innovative materials reach back into history to use old materials in new ways. Wool can be used for insulation. Instead of hardwood, try cork or bamboo. In a nod to the sod houses of the prairie and the adobe houses of the Southwest, rammed earth, mud brick, and straw bales are being used for structural walls because of their price, availability of materials, and natural insulating properties.
The specific cradle-to-grave costs of each material can vary by the application. A couple of central authorities on sustainability are: the US EPA’s Green Building page and Environment Canada’s Athena Institute for Sustainable Materials.
More good news is arriving. New materials like graphene and composites can dramatically decrease weight while increasing strength. Buildings can now by printed rather than constructed, drastically reducing material waste, time on site, and site impact. Energy solutions like solar panels incorporated into shingles, windows, and wall panels can turn negatives into positives by producing some of the energy needed to create the materials.
The right combination of materials may create a building that’s more sustainable than yesterday’s palaces and castles in many more ways than simply standing up for a long time.