As discussed on the Resource Use and Buildings page, good thermal performance of the materials in the building envelope can help the building save energy and is usually the most important factor in building material selection (for example, insulation or thermal mass).
Lifecycle Assessment is the most thorough way to determine the environmental impacts of your building materials. However, LCA can be very costly, varies project-to-project, and is not yet extremely prevalent. Instead, the building and building products industries have a host of measures and “certifications” for green building products. BuildingGreen’s Green Building Product Certification Guide is a fantastic resource for understanding this (sometimes intentionally) complex world.
Using Recycled Materials
To use recycled content in your building, call suppliers to source recycled materials. Be sure to verify the physical properties (strength, stiffness, etc.) of the material with recycled content. If they are lower-performance, you may need to alter your design to use slightly more material. This is usually still a net benefit environmentally. Perhaps the easiest way to create a large improvement from recycled content is in concrete, because it is used in such large quantities. Concrete can recycle fly ash from coal-fired power plants, and slag from the blast furnaces of steel production, among other materials. Be aware, however, that these materials may contain toxins like mercury; if so, they should not be directly exposed to occupants.Some building materials already have recycled content by default. For instance, most structural steel contains 90% recycled content, while sheet steel usually contains around 25% recycled content. Aluminum for curtain walls generally has no recycled content.
Making Recyclable Constructions
Materials are only recycled when the monetary value of the materials is greater than the cost to separate them out from other materials.To make your building (or parts of your building) recyclable, design for disassembly. That is, make it easy to separate different kinds of materials from each other. Some strategies for this include using as few different kinds of materials as possible, using undoable fasteners (e.g. screws rather than nails or epoxies), and using larger assemblies that have greater value than small pieces.
Reused materials are even more beneficial than recycled materials, because in addition to saving natural resources, they also require far less manufacturing. However, it may not be zero manufacturing. Reclaimed wood, for instance, is often planed or otherwise cleaned up for reuse.You can also make it easy to reuse the materials from your own building by designing for disassembly. This means using constructions that are easy to separate from each other.
Sustainably Harvested Materials
Rapidly Renewable Materials
The toxicity of a material is measured and published in its Materials Safety Data Sheet (MSDS). However, these documents can require chemistry expertise to understand.For those without toxicology expertise, some organizations and green building certification systems have created lists of substances to avoid. Here is once such list, from the Living Building Challenge:
- Chlorinated Polyethylene and Chlorosulfonated Polyethlene
- Chlorofluorocarbons (CFCs)
- Chloroprene (Neoprene)
- Formaldehyde (added)
- Halogenated Flame Retardants
- Hydrochlorofluorocarbons (HCFCs)
- Lead (added)
- Petrochemical Fertilizers and Pesticides
- Polyvinyl Chloride (PVC)
- Wood treatments containing Creosote, Arsenic or Pentachlorophenol
These substances are usually not advertised in products, but can be present as fire retardants, adhesives, stabilizers, refrigerant gases (“working fluids”), and other ingredients. Some of these substances are classified as Volatile Organic Compounds (VOCs) – which can slowly “off-gas” and can cause health risks in buildings that aren’t properly ventilated (see Indoor Air Quality).Even materials that do not cause concerns about indoor air quality for the building’s occupants can still carry toxicity risk for construction workers and manufacturing workers. Some materials can also leach toxins to groundwater when they are rained on.Manufacturers are starting to communicate more about the presence of VOCs in their products (like paints and composite wood products). However, some due diligence is required to ensure harmful chemicals and VOCs are not present in the products you source. In addition to lists referenced above, the health impacts of specific building products are becoming easier to understand and compare because of industry efforts like the Pharos Project (from the Healthy Building Network).
Local materials are any kind of material grown or manufactured within a certain radius of the building site. They are also called “regional” materials, because the radius is often large, such as 500 miles (800km).The goal of local material use is to avoid the ecological impacts of transportation, and to support local economies. For most materials, transportation is a much smaller impact than resource extraction and manufacturing, so it is a low priority environmentally (source – Journal of Green Building: Winter 2012, Vol. 7, No. 1). However, local materials’ benefit to local economies can be significant. One of the only ways green building certifications encourage local economies is by giving credit for local materials.