Our Back-of-the-Envelope calculator is a learning tool that allows anyone to interact with a building as an energy system. You can see real-time energy connections between building components, isolate the effects of changing a single energy parameter, or produce concept-level energy and CO2 emissions estimates. When it comes to building energy consumption, nearly everything affects everything. It's very difficult to get a feel for energy efficiency among the complicated interactions. Download the tool and additional climate data.