Energy Efficient Communities - A Collaboration Project of the International Energy Agency IEA

Since in general over 40 % of the end energy use in OECD countries is caused by the built environment, an increase of the energy performance in this sector, together with the increased use of renewables for electricity generation, will be the key to a successful energy and climate change policy in the industrialized world. 80 % of our built environment is located in towns and cities. For this reason, it is decisive that cities, small or large, will be able to achieve such ambitious energy goals, and this will entail enormous changes in urban fabric and urban energy use patterns in the future. During recent years, new energy standards like the German “Passivhaus” or the Swiss “Minergie”, or even “Net Zero Buildings”, have been introduced successfully, which have facilitated a reduction of end energy consumption by a factor of 2 or more compared to conventional new buildings. Is this the solution of the problem? Looking at the existing buildings in our cities and considering the fact, that some 80 % of them will still be there in 2050, and their current primary energy consumption for heating, cooling, hot water and electric appliances is in most cases beyond 300 kWhPE/m, a reduction by 80 % would require a primary energy use level of about 60 kWhPE/m. While this is technically feasible with today’s technologies, there are economic limits due to a non-linear increase of costs. To reduce the economic burden, cost-efficient alternatives must be found to simply decreasing Uvalues below economic limits.