You've probably seen phrases like sustainable design, green architecture, environmentally sustainable design, and other similarly sounding terms floating around the design sphere in recent years, and with good reason: according to the Environmental Protection Agency (EPA), as of 2014, construction and demolition generates more than twice the amount of municipal solid waste in the United States.

As a result of this fact and in the wake of climate change, natural disasters, and other environmental conditions, designers of all disciplines across the world are returning to design concepts that have been known for centuries, as well as newly discovered technical materials and ideas. These approaches all seek to reverse or reduce the effect that buildings, construction, and humans have on the environment. However, if you’re new to the concept of green architecture, the terminology used in reports and design coverage may be confusing or hard to understand. While there are dozens of terms and concepts to learn about and address, we decided to cover a few of the basics below.

Green Building Certification Programs

If you’ve heard of green design, you’ve most likely also heard of at least one of the green building certification programs. In North America, the most common programs are LEED: Leadership in Energy and Environmental Design, the Living Building Challenge, Passive House, Green Globes, Energy Star for Home, and Energy Star for Buildings. These programs are all third-party organizations (although Energy Star is a joint program of the EPA and the Department of Energy (DOE) that created their own rubrics or recommendations for assessing, implementing, or designing practical green building solutions. These solutions range from guidelines for whole buildings to ratings of individual products and appliances.

Although they've often been challenged for their piecemeal, sometimes arbitrary appearing approach, and unique requirements, green building certification programs have done wonders for the marketing and publicity that these projects and items have received, making names like LEED and Passive House terms that many are familiar with. Achieving certification can also add a layer of accountability and, at times, integrity for the project and the design team—but it certainly isn’t the only way to reach high-performing, sensitively designed spaces and products.

Carbon Footprint

Carbon footprint is another term that's frequently used when discussing sustainable design. Carbon footprint refers to the total amount of greenhouse gas emissions (gases like carbon dioxide that are produced through the greenhouse effect and have a detrimental impact on the environment by raising temperatures around the globe) that are caused by a person, event, product, or organization. As a general rule, the smaller the carbon footprint, the less greenhouse gases that are emitted, and the better the product or action is for the environment.

Carbon footprints are often mentioned when discussing both the creation and the use of a product. Usually, the manufacturing of an item “indirectly” creates greenhouse gases from the fuel burned to create or ship the product to the consumer, as opposed to “direct” greenhouse gases that are emitted during the use of the actual item, like the burning of gasoline in a car. Although carbon footprints are a critical component of sustainable design, they're complex and difficult to be precisely calculated.

Life-Cycle Assessment

A life-cycle assessment (LCA), also known as a life-cycle analysis, is a technique used by analysts and designers to understand the environmental impact of a product over the course of its entire “life.” A life-cycle assessment starts from the extraction of raw material of a product to its material processing, manufacturing, distribution, shipping, use, repair, maintenance, and eventual disposal or recycling. An LCA can help provide a long-term, comprehensive understanding of the inputs and releases of an item rather than a narrow, short-term view of a product.

For example, a life-cycle assessment allows designers and other professionals to compare two different options for wood shelves. One option might be bamboo, which is a renewable resource and grows quickly (but might have to be shipped thousands of miles to arrive at the client’s home), compared to solid maple shelving, which is grown locally and can be shipped less than 100 miles from its forest and manufacturing facility (but doesn’t grow as quickly as bamboo and isn’t always from sustainable forests). Sometimes, LCAs don’t lead to clear “right” or “wrong” answers, but instead allow for a more complex, nuanced understanding of an item.

Embodied Energy

Linked to LCAs is the term “embodied energy,” which refers to the total amount of energy that's required to produce any goods or services. This energy is viewed as embedded, or “embodied” in the product itself, and takes into consideration all of the energy that's required in the entire life cycle of the item, from its initial production through its demolition or recycling. In general, a product with a high-embodied energy (like a steel beam or column) will create more greenhouse gas emissions than a product with low-embodied energy (like concrete). Typically, natural materials will have lower embodied energy than man-made materials.

Interestingly, most of the focus when it comes to improving energy efficiency in buildings has been on the energy consumption during the operation of a building, i.e. after construction is completed and while it's in use, rather than the amount of energy that was required to complete the building and produce all of the materials and components needed. However, it's estimated that embodied energy accounts for about 30 percent of all energy consumed throughout the lifetime of a building—meaning that the consideration of embodied energy can have significant impacts on the amount of energy a building produces, and therefore carbon emissions.

Gray Water and Black Water

Gray water and black water refer not to the actual color of water, but rather to a classification of wastewater. Gray water is water that comes from sinks, showers, baths, dishwashers, and washing machines that can be reused (usually after treatment) for toilet flushing, irrigation, and other non-potable uses. The reuse of gray water is critical in many locations where access to fresh, clean water is limited and should only be used when necessary.

In contrast to gray water, black water is waste water from toilets, bidets, and toilet paper disposals that contains pathogens and other matter that can't be safely released into the environment without treatment. The organic material in black water makes it difficult to process, but with proper treatment and composting, can actually be reused for the nutrients found within. Regardless, the separation of gray and black water is often a critical component in ecologically oriented buildings and neighborhoods.