If you’re setting out to convert your home to a “zero energy” building standard, then it’s a good idea to know your baseline. In other words, where does the energy go in a typical home?
As you might expect, especially for heating cooling requirements, it depends on where you live, the age of your home, and to some extent (since the wealthy tend to consume more) how much money you make. However, one thing is clear, the bulk of the energy used in a home is for heating and cooling. According to the DOE, Energy Information Administration’s 2001 Residential Energy Consumption Survey anywhere from 38% to 70% of a homes energy consumption is spent on heating and cooling. The average values across all home sizes, home ages, and climate zones from that survey are shown in the following pie chart.
To give you and idea of how the energy consumption varies by where you live, the following charts show consumption by climate region for the United States.
The key point of all this data is that heating and cooling consumes the bulk of a home’s energy, and all of that energy is exchanged through the home’s shell or envelope. As a result, the starting point for any attempt to convert an existing home to a zero energy building standard must be an upgrade of the building envelope. In general, energy losses through the envelope are evenly divided between infiltration (air leaks), windows & doors, and conduction through the wall, ceiling, and floor. I’ll cover each of those in later posts.