Holistic energy retrofitting of multi-storey building to low energy level

The European building sector is responsible for about 40% of the total primary energy consumption. New buildings constructed every year represent about 1% of the existing building mass; hence, the energy-saving potential lies in existing buildings. Buildings with facades worth preserving cannot benefit from the application of large thicknesses of outside insulation to reduce the energy consumption.

Instead, inside insulation could be used in these buildings. However the thickness of the inside insulation should be kept at a minimum to avoid reduction of the floor area. This paper describes a holistic energy retrofitting of a multi-storey building from 1930 with facades worth preserving. Different single measures, e.g. windows and wall insulation, are assessed with regard to energy saving and economy.

The best performing single measures are combined in a holistic retrofitting. The total energy consumption of the holistic solution is theoretically calculated, and the economy is documented based on calculations of cost of conserved energy. The results show that many single measures are cost-effective.

However, when they are combined, the holistic retrofitting solution turns out not to be cost-effective with the actual energy prices on district heating, even though the energy consumption of the building can be reduced to 30 kWh/(m2•year).