Buildings use a lot of energy, so its no surprise they are responsible for many CO2 emissions. The challenge involves two tasks: creating new buildings that are zero carbon, and retrofitting all existing buildings to reduce and then eliminate their carbon footprint.
The first task is easier. Passive Homes need 90% less energy for heating and cooling by using super insulation and efficient heat recovery. There are 6,000 homes in Europe built to Passivhaus specifications. Future building codes should probably require that all new houses are built to this standard.
The challenge is tougher for existing buildings. Most building owners could achieve a 20% to 50% reduction in energy use by investing in new windows, super-insulation, heat-recovery systems, and efficient appliances and boilers. Solar PV and solar hot water can be added, and zero-carbon heat can be obtained from heat exchange with the air, earth, water, and sewage.
To encourage building innovation and rapid renovation, we need new programs, tax credits, self-financing mechanisms, and incentives to build differently. Its just a matter of vision and determination.