The effect on climate change impacts for building products when including the timing of greenhouse gas emissions

Greenhouse gases (GHGs) trap infrared radiation emitting from the Earth's surface to generate the "greenhouse effect" thus keeping the planet warm. Many natural activities including rotting vegetation emit GHGs such as carbon dioxide to produce this natural affect. However, in the last 200 years or so, human activity has increased the atmospheric concentrations of GHGs mostly from burning fossil fuels resulting in climate change (i.e. additional warming).;Global warming potential (GWP) measures the impact from climate change but does not consider the timing of the GHG emissions. Traditional (static) life-cycle assessments (LCAs) use GWP. However, GHG emissions for building products may occur decades after initial product production and installation. A new dynamic methodology was created for long-lived products using wood flooring as an example over a 100-year time horizon.;The new methodology demonstrated the time-dependent climate change impact metric using cumulative radiative forcing. Similar to the concept of net present value, time-zero equivalent (TIZE) generates a single value where future negative and positive radiative forcing impacts are brought back to year zero. TIZE 100 values for fossil carbon dioxide, methane, and nitrous oxide were found for two wood flooring products, prefinished solid strip hardwood (SSHF) and prefinished engineered wood (EWF). Results were reported in kg CO2-eq per functional unit of product for TIZE100 and GWP100. The functional unit was one m2 of installed flooring in service for 80 years. The service life for SSHF and EWF are 80 and 40 years, respectively. TIZE100 values were less than the GWP100 values. For SSHF, GWP100 and TIZE100 values were 20.9 and 15.6 kg CO2-eq per functional unit, a 25% decrease. For EWF, GWP100 and TIZE100 values were 34.7 and 28.9 kg CO2-eq per functional unit, a 17% decrease. SSHF had the greatest reduction for TIZE mainly because of its longer service life resulting in less GHG emissions at end-of-life.;Including timing of GHG emissions by using the TIZE (dynamic) methodology provides greater precision on the impacts of climate change than GWP (static) does. Additionally, because TIZE and GWP use the same reporting unit, kg CO 2-eq TIZE could be an alternative to GWP.