Structural Design for Adaptability and Deconstruction: A Strategy for Closing the Materials Loop and Increasing Building Value

Structural engineers sometimes wonder what they can do to advance the practice of "sustainable" or "green" design. While for building design it is true that the architect and mechanical engineer tend to play larger roles than the structural engineer, the structural engineer can contribute in a number of significant ways. For example, designing efficient structures and using recycled and salvaged materials conserve non-renewable resources. One emerging strategy with far-reaching consequences is Design for Adaptability and Disassembly (DfAD). DfAD may in fact be the most important strategy we can use to conserve materials, thereby reducing the energy consumed and the pollution and global warming gases emitted during their extraction and manufacture. Applying these strategies should greatly increase the probability that (1) the life of the structure will be extended, and (2) at the structure's end-of-life the materials will be reused or recycled. Adaptability is a measure of how easy it is to modify a building during the course of its life. One recent study of demolished buildings in Minnesota found that only about 40% of the demolitions were due to the building's physical condition. The remainder were due to factors such as neighborhood redevelopment and suitability for a desired use. Stewart Brand's book. How Buildings Learn, leads the reader through the lives of many different types of buildings, and demonstrates that most long-lived buildings undergo changes during their lives, such as changes in use, upgrades to facades and mechanical systems, and additions. Buildings that cannot adapt, die. If the costs of making the changes that the building users demand exceed the cost of building from scratch, the older, non-adaptable, building is likely doomed, and the materials in that building either wasted or, at best, recycled. Deconstruction is a demolition method whereby a structure is carefully and methodically disassembled so as to salvage as many components as possible. The goal here is not merely to recycle, but to reuse. Recycling is certainly beneficial, in that it conserves virgin resources, but recycling also can consume large amounts of energy and produce significant pollution. Reuse, on the other hand, requires no re-manufacturing, and therefore has a much lower environmental impact. Often the impact is limited to transportation, such as moving materials from the site of a former use to the site of a new use, perhaps with an intermediate stop at a materials storage site or a refurbisher's shop.