Design Choices Involving Sealants and Adhesives in Building Construction and Their Impact on our Environmental Footprint

Whether sealants and adhesives will be seen from an ecological point of view as being part of the solution or part of the problem – especially when one considers recycling of materials and components at the renovation or demo­lition stage – depends largely on decisions made during the design phase.

First, it should be recognized that, even if the design process itself had only a minor contribution to the cost of building, a considerable portion of the cost (as well as material and energy use) associated with later life cycle phases is committed at the design stage. It has been estimated that more than 80 percent of a product’s environmental impact is determined during its design phase[15] [16] [17], and it is likely that the same holds true for buildings. Therefore, it is essential to consider environmental aspects of the whole buildings as well as of the components and materials used from the first stages of design and de­velopment. Such an approach is generally termed ‘Eco-innovation’ or ‘Design for Environment (DfE)’. The purpose of Design for Environment then is to design a building in such a way as to minimize (or even eliminate!) the envi­ronmental impacts associated with its life cycle. Design for Environment, as applied to buildings, typically focuses on energy efficiency and effectiveness, materials innovation, and recycling. While energy efficiency often is under­stood as addressing energy savings at the sub-system level, for instance in terms of the heating, ventilation and cooling (HVAC) system, energy effec­tiveness may be defined as producing the best overall results with the least amount of energy. Materials innovation addresses the need to develop new materials that allow construction of low embodied energy, light weight, and durable components which also meet the need for improved recyclability (which often is a challenge with composites) and have less environmental impact. Recyclability finally is considered at the design stage by ‘Design for Deconstruction (DfD)’. Design for Deconstruction is an emerging concept that borrows from the fields of design for disassembly, reuse, remanufac­turing and recycling in the consumer products industries1617. According to the ISO 14021:1999 standard “Environmental labels and declarations – Self­declared environmental claims (Type II environmental labeling)”, the use of the term ‘design to disassemble’ refers to the design of a product that can be separated at the end of its life-time, in such a way its components and parts are reused, recycled, recovered as energy form, or in some other way sepa­rated from the remainders flow. The overall goal of Design for Deconstruc­tion is to reduce pollution impacts and increase resource and economic ef­ficiency in the adaptation and eventual removal of buildings, and recovery of components and materials for reuse, re-manufacturing and recycling. From

an environmental point of view, building adhesives and sealants often face two contradicting requirements: On the one hand, these materials should be durable and resist the environmental stressors, such as sunlight, water, and heat; on the other hand, there is the need to easily separate substrates for recycling or repair. Recently, there has been increased interest in ‘Debonding on Demand’, which refers to the process of easily separating two adhered surfaces. Heat and light switchable adhesives have been developed, as well as primers that can act as a separation layer when activated by infrared or microwave radiation181920. Surely novel methods for Debonding on Demand will be developed in the near future and it will be interesting to see what the environmental durability of these sealants and adhesives will be.

Returning to the topic of dematerialization, it should be noted that less material use does not automatically imply less environmental impact. If the dematerialized product or component is inferior in quality and has a shorter usable life, then more replacements will be needed during the over­all life of the building, and the net result likely will be a greater amount of waste in both production and use. Design for Dematerialization, therefore, must always be accompanied by Design for Reliability and Durability, i. e., designing a product or component to perform its task in a reliable, consist­ent manner, and ensuring that it will also have a long life span. From an environmental viewpoint, therefore, dematerialization should perhaps be better defined as the reduction in the amount of waste generated per unit of building product.

When considering Design for Durability, a fair question to ask is: What should be the design life of a building or a material or component used in the building? Clearly, there is a trade-off between the embodied energy in the building and its energy efficiency and effectiveness. Building components that are still far from being fully optimized in terms of their impact on ener­gy efficiency should not last forever; rather they should be easily replaceable with new, more efficient components and easily recycled at the end of their life. Obviously, the corollary to this statement is that the higher the energy efficiency associated with a building component is, the higher its expected service life should be. The same holds true from an economic point of view: The higher the investment cost, the longer it takes to recover the invest – [18] [19] [20]

ment, the higher the durability of the component should be. Consequently, recyclability is more important for short-lived products and components than for more durable ones.

Another, very effective approach to dematerialization is moving from a product to a service orientation, i. e., using less material to deliver the same level of functionality to the building owner. After all, building own­ers and users are more interested in the value a product provides than in its physical presence. For example, the newly published ASTM Stand­ard C 1736-11 “Practice for Non-Destructive Evaluation of Adhesion of Installed Weatherproofing Sealant Joints Using a Rolling Device” offers the sealant applicator an opportunity to move from installation contracts to product-oriented service contracts. Probably most applicators will ini­tially view the concept of inspecting the quality of installed joint seals as challenging their reputation, possibly resulting in increased liability for them. However, when this inspection is offered as part of a periodic maintenance contract, sealant failures can be repaired locally and without replacing the entire installation. Such maintenance results in material savings as well as satisfied building owners (and facility managers), as the functionality of the seals is ensured and maintained at a high level, and, ultimately, also results in better and more stable relationships between sealant applicators and their clients due to the more frequent contacts and the higher value provided. Similarly, sealant manufacturers initially will be concerned that such service contracts will lead to decreasing seal­ant product sales. However, revenue models could be developed that allow extension of sealed joint warranties based on certification fees associated with the inspection of the building.