Planning for deconstruction: What’s next for construction and demolition recyclers?
Tuesday, February 17, 2015
Posted by: Anne Piacentino
Source: American Recycler
by MARK HENRICKS
Buildings today are designed for easy, cost-effective construction, with little attention paid to how costly and difficult it might be to someday demolish structures and recycle construction materials.
A different approach called designing for deconstruction is an emerging discipline that could significantly increase the quantity and quality of materials recycled from demolition.
As described in a recently issued report from VTT Technical Research Centre of Finland, designing for deconstruction requires going beyond using recycled and recyclable materials. In addition, this expanded cradle-to-grave thinking would allow for easy disassembly by, for instance, using bolts or screws to connect building
“Proper design for future deconstruction will greatly reduce the time and effort needed to dismantle the building frame,” commented Petr Hradil, VTT research scientist. “It will also affect the life cycle impact of the building because all of the embodied energy and carbon content is retained.”
Designers and architects today are beginning to consider future ability to recycle building materials when they design structures. One way this can be done is by using materials that are more readily recycled. For instance, metals are generally much easier to recycle than plastics, noted Richard Diven, managing partner of R.J. Diven Consulting, a Coeur d’ Alene, Idaho, a demolition consulting firm.
“Metal is very recyclable,” Diven said. “Virtually 99 percent of metals are recycled now.” However, considerable amounts of plastic materials such as polystyrene foam insulation are also being used in buildings, Diven said. “They’re difficult to recycle, at least in the older buildings that have them,” he said of plastics.
One reason plastic building materials can be difficult to recycle is that it is challenging to separate them from other materials. Often, plastics are glued or otherwise attached to other materials using adhesives and techniques that make it hard for recyclers to separate economically. In the vision VTT put forth, designers and architects would minimize chemical connections, as well as specifying adhesives, sealants and other fasteners that would be more readily disassembled when the building’s lifespan was complete.
Another key element of the design for deconstruction principles developed by VTT is to document the materials and methods used in construction, and retain this documentation to make it available for future demolition. “The availability of information about the material quality, components, sizes and manufacturing process at the time of their reuse can further reduce the costs associated with material testing and quality checks,” Hradil said.
VTT’s deconstruction plan also calls for keeping designs simple when possible, ensuring that connections between building elements are accessible, separating mechanical and electrical and plumbing systems, using elements that can be interchanged, and generally thinking of future deconstruction to make it as efficient, affordable and safe as possible.
Designing for deconstruction is likely to have the most impact on designs for certain types of buildings. These include warehouses, schools, supermarkets and stadiums. That forecast is based on expected life spans of these types of buildings and the materials and methods used to construct them. Generally, designing for deconstruction is of less importance for very long-lived structures, such as museums.
The nature of a building’s environmental effect, including emissions and carbon impact, is also of concern. For instance, a warehouse requires comparatively little energy for operation, so the carbon embedded in its materials makes up as much as 60 percent of the building’s lifetime carbon impact. Embedded carbon in an office building, on the other hand, may amount to just 45 percent of its lifespan carbon impact, so planning for deconstruction is less critical with this type of building.
Planning for deconstruction today is generally limited to specifying recyclable materials. Diven, who has worked in demolition for more than 50 years, said he has never been asked for advice on designing a permanent building to facilitate demolition. However, he noted, the practice of thinking about eventual demolition during design is decades old when it comes to materials. Examples include the long standing restrictions on use of lead paint, asbestos and other materials that can pose a hazard to demolition workers and others.
Diven said economic and market pressures and the difficulty of planning for a demolition process that may not happen for decades keep design for deconstruction out of the mainstream for architects and engineers. “The problem is the goal is to sell the structure and satisfy the client,” he said. “I don’t know if most people think out 30 to 40 years.”
Modular building techniques are becoming more common, however, and they can greatly facilitate deconstruction and allow for re-use of modular components for other structures. “We have dismantled buildings, taken them apart and resold them to be re-erected somewhere else,” Diven commented.
Sustainable building certification systems such as Leadership in Energy and Environmental Design (LEED) in the U.S. and the European Building Research Establishment Environmental Assessment Method (BREEAM) incorporate some elements of designing for deconstruction in assessments and ratings, which encourages architects, designers and owners to think about the topic, Hradil said. He anticipates these types of standards, and others even more encompassing, will eventually show up elsewhere. “The design for deconstruction may be part of the future building codes or as one of the requirements for building permits,” he commented.
Ultimately, designing for deconstruction could meaningfully increase the amount, quality and value of recyclable materials recovered from deconstructed buildings, while reducing the time, effort and cost of recovering them. That could allow companies that specialize in recovery and recycling of construction and demolition (C&D) materials to make much more cost-effective bids on demolition jobs, Diven said, because the value of the materials recovered is a major element in estimating such bids.
Hradil predicts that in 2020, over 70 percent of C&D materials in Europe will be re-used or recycled. Hradil feels that at that point, design for deconstruction will be a more widespread practice. “We think that the architects, designers and owners should think beyond the deconstruction by proposing the possible scenarios for the future utilization of dismantled building elements,” he said.