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July 6, 2011 -
Energy Efficiency ✉ Email The Editor
Today's tip is about the industry-standard definitions for various types of net-zero energy buildings. As net-zero energy buildings increase in prominence - with the expectation that they’ll be code-mandated some time in the future - standard definitions for what exactly makes a net-zero energy building are critical.
Currently, there are four main types of net-zero energy buildings. Let's take a look at each.
1) Net-Zero Site Energy buildings is the most common type. This is a building that produces at least as much energy - through on-site renewables - as it uses on a yearly basis.
2) Net-Zero Source Energy buildings are buildings that produce as much energy as they use when calculated at the source. What that means is that the building’s produced energy must also make up for energy lost in transmission from the source of the energy the building does use.
3) Net-Zero Energy Cost buildings are those in which the amount of money an owner pays for electricity a building uses is equal to the amount of money the utility pays the owner for renewable energy the building feeds to the grid.
4) Net-Zero Energy Emissions buildings produce and export at least as much emissions-free renewable energy as they import and use from emission-producing sources on an annual basis. According to sources, this is the easiest type of net-zero energy building to achieve, and therefore may be the least environmentally stringent.
Strictly speaking, these definitions do not include buildings that purchase renewable energy certificates (RECs) or carbon offsets to make up a gap between a building's energy use and its production. Nor should buildings that use of those make-up measures be included, say most experts. But stayed tuned as these definitions evolve.