Energy modernisation

Within the scope of conversion and extension measures of a school building complex in prefabricated construction built in 1978, an energy consultation with subsequent detailed energy planning was to be carried out by bfl | Architekten und Berater.

After an intensive inventory, the entire thermal envelope was recalculated and concrete improvement measures were proposed. For this purpose, thermal bridges were simulated in detail and designed to be safe in terms of building physics.

The entire building envelope was uninsulated at the time of the inspection. At building corners, where the heat-emitting surface is greatest, or at interfaces between e.g. storey ceilings or internal walls and external building components, there were numerous thermal bridges due to the construction.

The main heat losses were caused by the heat transfer, the so-called ‘transmission’ at the uninsulated outer shell. Additional losses occurred due to uninsulated heating pipes during heat distribution.

Overall, the comfort and thus the comfort of the users was considerably limited by cold areas on the exterior wall in winter and overheating in summer.

According to our new building component dimensions, the single-shell precast concrete elements of the exterior walls were insulated and clad with rear-ventilated clay panels. The existing district heating station for generating heat for the heating system was renewed, heating pipes insulated, and radiators and thermostatic valves replaced. A decentralised instantaneous water heater replaced the existing hot water tank.

Due to the good condition of the windows, which were renewed in 2001, they were retained in their existing state, and external sun protection was retrofitted to the generous window strips. In some highly frequented common rooms, a mechanical ventilation system with heat recovery now regulates the exchange of fresh air through decentralised ventilation ducts installed in the window frames.

Before the renovation, the school building’s annual primary energy demand was about 30% higher than the value required by the EnEV for modernised old buildings. In the refurbished state, it improved by around 40%. This also significantly reduced the running costs.