Greenhouse Gases (GHGs) are gases that trap heat in the atmosphere. For each Greenhouse Gas, a Global Warming Potential (GWP) has been calculated to reflect how long the gas remains in the atmosphere, on average, and how strongly it absorbs energy. Gases with a higher GWP absorb more energy, per pound, than gases with a lower GWP, and thus contribute more to warming the Earth. The excess accumulation of GHGs is what causes Global Warming via the Greenhouse Effect. Reducing GHG emissions through improved design strategies and material selection is the best approach the AEC industry has to prevent climate disasters and Fight Global Warming.
Carbon Dioxide and Other Greenhouse Gases
A GWP is expressed as the equivalent tons of CO2e, Carbon Dioxide and Equivalent Greenhouse Gases (GHGs), generated from the beginning to end process of enacting human activity. A common misnomer about the expression CO2e is that the "e" stands for embodied when in reality, the "e" stands for equivalent and represents all non-CO2' GHGs emitted throughout a building product's lifecycle. Roughly 80% of GHGs will be Carbon Dioxide, and the remainder makeup is a combination of Methane (CH4), Nitrous Oxide (N2O), and Fluorinated gases (industrial synthetic gases such as Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), Sulfur Hexafluoride (SF6), and Nitrogen Trifluoride (NF3)).
GHGs and Embodied Carbon
When applied to the AEC industry, GHGs used to calculate the building's Embodied Carbon for each stage of the Life Cycle Assesment. Embodied Carbon can represent any phase of the building life cycle, but only a full assessment from A1 (extraction) to A7 (end-of-life) is called an LCA or Life Cycle Assessment. The diagram below shows the 7 stages of the LCA: the extraction, manufacture, transportation, construction, replacement, and deconstruction of building materials, together with the end of life emissions.
Where to find GHGs values?
The standard building material does not have a known Embodied Carbon value, however, the metric has gained popularity through the growing recognition and code/certification requirements of Environmental Product Declarations (EPDs) and increased demand for Lifecycle Assessments (LCA's).
EPDs are a standardized assessment of a product or building system's effect on the environment. The assessment includes declaring the product's or building system's global warming potential (embodied carbon). Although a variety of EPD programs exist, a verified EPD will follow the ISO (International Organization for Standardization) 14025, 14040, 14044, and EN 15804 or ISO 21930 and have at least a cradle-to-gate scope. Manufacturers who have undergone the process to declare their products will typically list these forms as .pdf files on their websites. So when searching for your ideal product properties for cove.tool's optimization, searching "Manufacturer Name" + EPD will help determine whether such a document exists.
Once you have found an EPD, the next step is locating the Embodied Carbon value. Below are two tables are taken from example EPDs found online. The first is a glazing product (EPD) from a GuardianGlass. The second is a wall insulation product (EPD) from CertainTeed-SaintGobin. In both examples, the embodied carbon value is written as the Global Warming Potential (GWP) and has columns listed for different stages of the life cycle assessment. Before you start selecting your embodied carbon value, make sure that this row also uses the same units as embodied carbon, kgCO2e[q]. To calculate the embodied carbon value required for the cove.tool optimization only selects, or add up, the GWP value from the cradle-to-gate stages of the table. We have highlighted which sections below. If you did it correctly the embodied carbon for the Glass product (above) is .00145 kgCO2e, and for the Insulation product (below) is 0.94 kgCO2e.