Worldwide, buildings account for 32 percent of energy use and 19 percent of energy-related greenhouse emissions. They pull from the electric grid or natural gas lines to heat, cool, and light the spaces within them and to power appliances and machinery. As much as 80 percent of the energy consumed is wasted—lights and electronics are left on unnecessarily and gaps in the building’s envelope allow air to seep in and out, for example.
Much of the attention paid to green buildings is in new construction, but retrofitting brings energy efficiency to the existing built environment. The world has 1.6 trillion square feet of building stock, 99 percent of which is not green. Retrofitting addresses how heat and cold are escaping or entering the building, the systems that cool or warm inhabitants, and how spaces are illuminated. It ultimately improves the experience of being inside the building.
Retrofitting is a well-understood practice, and good building performance data is making it increasingly effective. The payback on retrofits, depending on the building, is five to seven years on average. A recent retrofit of New York’s iconic Empire State Building will cut energy use by 40 percent and avert 105,000 tons of greenhouse gas emissions.
As with net zero buildings, there are no results presented from our models here. Building owners who retrofit existing residential and commercial building space install better insulation, improved heating and cooling equipment, upgraded management systems, etc. These solutions are accounted for individually. No retrofit will look exactly the same, making forecasting costs and savings nearly impossible.