.

Evaluation of the comfort air temperature during the usage period in accordance with DIN EN 15251
© FhG-IBP
2 / 3

Results of the monitoring

The monitoring aimed to provide, on the one hand, specific recommendations for the client and operator in order to improve the operation and, on the other hand, general knowledge for future school buildings. Owing to delays in the construction and the insolvency of the main design team, the regular data collection for monitoring did not begin until the end of 2015. Results are now available up to March 2018.

The research team from Magdeburg-Stendal University of Applied Sciences compiled the data from five sources:

The central monitoring server with the measurement stations for the intensive monitoring, the existing storage units for the two central ventilation systems as well as the solar thermal and photovoltaic systems, and the electricity meter data from the Stadtwerke Halle municipal utility company.

The following detailed evaluations are thus possible: annual overviews of the energy and media flow, evaluation of the indoor climate parameters with in-depth analysis of two classrooms and the assembly hall, measurements of the renewable energy and ventilation technology efficiency, and measurements of the building envelope.

Energy flow maps for the district heating, electricity and water/rainwater were created. The following results are becoming evident:

  • With the heating deployment, 75% is useful heat with 25% network losses. The high network losses are due to the fact that the main district heat supply is located 70 metres away and the underground heat pipes are therefore correspondingly long.
  • The largest heat loads are the two central heating auxiliary heat exchangers for the assembly hall, administration and corridors with a total of 56% of the useful heat consumption for approximately 41% of the total area. These are closely followed by the central air heating system for the classroom area.
  • The measured heat consumption amounts to approximately 14 kWh/m2p.a., including network losses. The primary school therefore consumes only about 10% of the national average for primary schools in Germany and achieves the Passive House level.
  • The photovoltaic plants achieve an average annual electricity yield of 81 MWh/p.a. The self-utilisation rate for the generated electricity is about 52%.
  • The electricity consumption amounts to an average of 110 MWh/p.a., of which approximately 60% is drawn from the electricity grid and the remainder is produced via the PV systems on site.
  • The largest electricity loads, which account for almost 50% of the total electricity consumed by the school building (without kitchen), are the two central ventilation systems. The chosen concept leaves, however, little scope for optimisation; it is recommended that the heating and ventilation functions should be separated in future projects.
  • The solar thermal energy delivers up to 214 kWh/m2p.a. relative to the aperture area, which corresponds to expectations.
  • The water consumption for the entire building in 2017 amounted to 776 m3/p.a., 70% of which was purchased as drinking water while the rest was collected as rainwater and used as process water for the toilet facilities. During the course of the monitoring it was revealed, however, that the costs for operating the pumps for the rainwater harvesting system are very high, so that it is still unclear whether this concept will continue to be operated.

Good air in classrooms

Many different studies show that there is a link between the classroom air quality and students‘ performance and concentration. The ventilation system with heat recovery ensures sufficient fresh air in the classrooms. This ensures a hygienic indoor air quality and also allows the temperature in the rooms to be controlled. In St. Francis Primary School it is also possible to supply fresh air via the box windows. To prevent the classrooms from overheating in summer, the excess heat in the window cavity can be released by tilting the outside windows. In winter, the solar gains can be fed into the room by opening the inner windows.

In winter, the geothermal heat exchangers pre-heat the outside air, which means that less energy is required for auxiliary heating. In summer, the outside air is pre-cooled by the geothermal heat exchanger. The passive cooling of the building using night-time ventilation in summer is showing some very good results.

The air quality of the classrooms is rated as very good with hourly average CO2 values during the usage time of <1,000 ppm. Although the Pettenkofer limit was exceeded in up to 41% of the usage time, the values usually remained below 1,500 ppm, which – especially when compared with manually ventilated schools – corresponds to a good air quality.

Results of the accompanying sociological research

The evaluation compared the surveys of the school pupils and teachers as well as the group discussions. The results show that both the students and the teachers are positive about the new school building and feel comfortable in the building. One criticism is that it often gets too warm in the classrooms in summer. Students and teachers then feel that the air is too stuffy. Conversely, it was revealed during the group discussions that the north-facing rooms for the after-school care centre were perceived as too cold during the winter holidays. The problems were partly due to faulty ventilation regulation. This was identified and remedied as part of the ventilation optimisation. It turned out that the regulation had mixed up the northern and southern rooms in the after-school care centre. At times the nighttime ventilation during the summer was also inadvertently deactivated. Despite ventilation optimisation, the locally chosen concept – with a uniform supply air temperature for all rooms – means that unequal heating of the northern and southern rooms cannot be avoided. Some teachers complain that particularly the interaction between the blinds, windows and lighting control is not self-explanatory. Simple operating instructions were therefore created as part of the monitoring.

notepad

BINE subscription

Subscribe to publication

Links

St. Francis Primary School
Website of the primary school in Halle (in German)

ENERGIEWENDEBAUEN
Projects, reports, news and analysis from the research initiative ENERGIEWENDEBAUEN