Annual balance of the final energy in comparison to existing building stock and the demand predictions (based on the reference climate in Potsdam); there is no energy consumption measurement data for the existing stock. Thanks to the primary energy factor of 0 for the district heating, the solar power, which is mainly used on site, and the refurbishment of the building envelope an energy plus level has been achieved.
© Future Energy – Institute for Energy Research (iFE)

Use of the ceiling fans depending upon the outdoor or indoor air temperatures during the usage period. In the event of indoor air temperatures over 26 °C, the ceiling fan was activated for up to 97 % of the usage period.
© Harald Semke, pape oder semke ARCHITEKTURBÜRO

Installers fit the prefabricated modules; they are then filled with cellulose.
© Harald Semke, pape oder semke ARCHITEKTURBÜRO
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Tricky commissioning of the heating

Without additional expense, the existing heating circuit in the old buildings could only be controlled in a building specific manner because the distribution is carried out as a Tichelmann system. The classrooms in the basement, the computer rooms, the standard classrooms and the staffroom are on the same heating circuit. The option of adapting the temperatures in the rooms is limited to the individual settings of the existing (authority’s) thermostatic valves and the operating time of the heating. One disadvantage is the position of the thermostatic heads because some of them are  situated in an alcove or are covered by window sills or cable channels. That can lead to a microclimate that is different to the centre of the room and prevents a fast reaction to the room temperature.

The new room thermostats recommended in the technical plan to allow users individual access were initially not implemented for reasons of cost because within the planned monitoring and optimisation phase and after hydraulic balancing plus the reduction of the supply temperature, this investment can possibly be saved.

A modified operation is necessary so that at the start of lessons there is a room temperature of approximately 21 °C, even in the classrooms in the basement, which lose heat through the non-insulated floor slabs. Different specified room air temperatures have been set on the thermostat valves for the heating-up process in the morning: 20–22°C in the standard classrooms, 17 – 19 °C in the computer rooms and 26 °C in the basement rooms. After 2 hours of heating up in the morning, the heating circuit generally switches to reduced operation because the internal loads in the rooms, even in the basement, are almost enough to maintain 21 °C. Without the classrooms in the basement, the heating operation during the day would not be needed at all.

The intensive monitoring in combination with room simulations have made it possible to incrementally approach an optimum operation of the heating by way of adaptations during the ongoing use of the buildings. For that reason, a sticking point will again be the handover to the caretaker or building operator.

At first, users assessed the air quality as worse than expected

Employees at the Institute for Resource Efficiency and Energy Strategies (IREES) regularly surveyed students and teachers in order to record the perceived comfort before and after the refurbishment. According to the survey, the users were primarily unhappy with air quality after the refurbishment. They gave it a school grade of D plus, even though during most of the usage period a CO2 concentration of less than 1,000 ppm was recorded and 1,500 ppm was only rarely exceeded. Measurements verified the critical air humidity conditions in the winter: the outdoor airflow of approx. 20 m³/h per person led to a relative air humidity of only 20 to 30% during approximately one third of the usage period – a typical problem with mechanical ventilation. After the adaptation of the heating control system and the reduction of the maximum flow rate to 12 m³/h, not reach- ing the threshold of 40% occurred considerably more rarely. Currently, the scientists are investigating how to permanently guarantee sufficient relative air  humidity with a simultaneously lower CO2 concentration.

User information necessary

In order to be able to use the funds from the German government’s Economic Stimulus Package II, the buildings were initially expanded. The lengthy application for and approval of research funding for innovative components prevented the seamless start of the energy refurbishment. Furthermore, insolvencies also markedly delayed the project. Parallel to the optimisation in terms of energy, the internal visual and technical refurbishment as well as the refurbishment of the drainage for the whole campus were carried out. These large construction measures during the ongoing use of the buildings over such a long period of time unavoidably led to decreasing tolerance as well as criticism on the part of the users. Regarding participation, the school was represented in all regularmeetings from the first briefing, concerning all sketches and performance phases of planning and implementation. Information events were also held for the teaching staff.

the ongoing use of the school, a communication and participation policy is necessary. In projects of this kind dialogue is essentially to be sought with the users as soon as possible after completion in order to provide information about changes and how to use rooms and installations. The responsible personnel must be given technical support especially in the first months of the heating season and the summer operation in order to correct short-comings at an early stage and in this way to avoid bad feelings and misjudgement in regard to the building from the very beginning.

Facade insulation – life cycle in focus

Special attention was paid in the project to maintaining the existing construction and to using resource-saving materials. On the basis of life cycle analyses, prefabricated modules using a timber panel structure with thermal bridge-optimised timber I-joists filled with cellulose were selected for the facade insulation. The elements were developed and produced with the help of a 3D scan of the building. It allowed the dimensional tolerances of the uneven, slanting and highly varied existing walls to be taken into consideration. The prefabrication made it possible to limit the insulation work to the summer holidays.

In energy research, there has also been international focus on life cycle analysis. Since 2016, more than 20 countries have been cooperating on EBC Annex 72 of the International Energy Agency on the topic of “Assessing Life Cycle Related Environmental Impacts Caused by Buildings”.

Projektinfo 09/2018:
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BINE-Projektinfo 09/2018
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Energy-efficient schools
Final report for the research project "Energy-efficient schools" (in German)

EBC Task 72
Website of the International Energy Agency for the subject "Assessing Life Cycle Related Environmental Impacts Caused by Buildings"

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