Energy use in buildings worldwide accounts for over 40% of primary energy use and 24% of greenhouse gas emissions . Energy use and emissions include both direct, on-site use of fossil fuels as well as indirect use from electricity , district heating/cooling systems and embodied energy in construction materials.
Given the global challenges related to climate change and resource shortages, much more is required than incremental increases in energy efficiency. Currently, a prominent vision proposes so called "net zero energy", "zero net energy", "net zero carbon" "net zero energy buildings NZEB", or "EQuilibrium" buildings . Although these terms have different meaning and are poorly understood, several IEA countries have adopted this vision as a long-term goal of their building energy policies .
What is missing is a clear definition and international agreement on the measures of building performance that could inform "zero energy" building policies, programs and industry adoption.