Budgeting for carbon in construction projects

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In the construction field, there recently has been emphasis on obtaining “net zero energy” (often referred to as NZE or net zero metering) for both new and existing buildings. However, depending on the materials used, the way we achieve net zero can create higher greenhouse gas emissions than continuing to build and operate buildings as we currently do.

In today’s built environment, decisions are often based on short-term financial cost, with little to no consideration for the long-term impacts of the material choices. These decisions may have significant negative effects on manufacturers, installers, occupants and the environment.

It is widely accepted that 39% of all carbon emissions are related to the building industry, this number accounts not only for operations, but also the embodied carbon of the materials chosen. As the construction field increases focus on NZE, the importance of material choice becomes more significant, because when CO_2e (CO₂ and equivalents) is measured comprehensively, we find that mining, manufacturing, transport, construction waste and decommissioning/demolition are significant sources of greenhouse gas emissions.

It is sometimes said that “the most environmentally friendly building you can design is the one that never gets built.” This statement should be taken as a challenge by all architects, engineers and builders. Steel, aluminum, concrete and foams are some of the highest embodied carbon materials used in construction today. When we reduce the amount of these materials required in our buildings — or replace these products with less carbon intensive, more biophilic materials (which store more carbon than they take to produce) — we can strive to balance the total embodied carbon to net zero or below. Doing so would create buildings that are not merely carbon neutral, but instead act as carbon sinks.

This will take effort from architecture, engineering and construction professionals. When new materials come to market they are often presented as “sustainable” or “green,” but these labels seem to have lost all meaning as definitions are manipulated to support a sales pitch. Though harder to find in the United States, many manufacturers around the world use Environmental Product Declaration (EPD) labels on their products. These labels detail the embodied carbon of the product based on verified results of Life Cycle Assessment (LCA).

The LCA, however, only takes into consideration “cradle to gate” and does not account for transportation from the factory to distributors and onsite, along with any associated emissions required for installation. More research and verification may be required on the part of design and construction professionals when no labels are provided.

When the choice is made to build with responsible materials — and construction details are chosen, created and executed properly — the cost of construction may increase, but decreased operational costs often recover the construction losses.

Additionally the reluctance to adapt to carbon calculations in buildings may result in financial impacts for businesses as industry regulations shift toward a more cost-effective equation, which potentially calls for carbon pricing. As the building industry becomes more aware and educated about the embodied carbon impacts, new methods and materials will become commonplace, and computer modeling can run LCA to determine a rough estimate of what the overall carbon impact is, making it easy to move forward with carbon beneficial designs.

Eric Menz, RA, is a licensed architect with a focus on low-impact and high-performance design, build, and consultation.