Use fewer construction materials and ensure that the materials used have low embodied energy to significantly reduce short-term emissions.

The harvesting and manufacturing of building materials, and renovation and demolition of buildings is responsible for approximately 10-20% of all human-made greenhouse gas emissions (Yamamoto, 2009). The embodied carbon of construction materials, depending on a building's efficiency, can account for between 20-100% of the building's total lifetime emissions (Giesekam et al., 2016).

In an energy efficient building, even after 15 to 20 years of operation, the majority of emissions will still be caused by the original embodied carbon in the materials (Strain, 2017). Like compounding interest, embodied carbon avoided at the start of the building's life will have a greater beneficial effect than emissions saved later.

There are several ways to lower the embodied carbon of an assembly:

• Reuse and renovate existing structures
• Minimize waste
• Use less new materials
• Source new materials that are produced with less energy intensive processes and have higher recycled content
• Use plant-based materials that have a negative embodied carbon value

Doing so can provide significant short-term carbon-emissions relief and result in a building that operates from the start with a negative carbon balance. Because the embodied carbon in the structure of a building can account for as much as half of the building's total carbon emissions, retrofits maximize a high performance building's immediate carbon savings (Kaethner, Burridge, 2012).