High School Broye (GYB) Payerne

The High School Broye in Payerne is a secondary school and offers various post-compulsory courses in its catchment area from Moudon to Cudrefin. The building complex is located in the north of Payerne and comprises classrooms, an assembly hall, laboratories, conference rooms and a library with a capacity for around 1000 pupils. The GYB was opened in 2005 and due to the growing number of students in the following years, an extension with a site area of 10,000 m² was approved in 2019. The extension includes new versatile classrooms and a sports hall.

In 2022, Gruner Gebäudetechnik Bern was asked to provide building climate consulting services and thermal-energy building simulations.

The classrooms on the south and south-east sides of the building were experiencing uncomfortably high indoor air temperatures during the summer months. An already known problem was the existing fabric sun protection, which opens even at relatively low wind speeds and exposes the classrooms to the sun. The situation was exacerbated by the fact that the region and the school are situated in a wind-exposed location. In terms of building technology, the rooms have no active cooling source or only a ventilation system with heat recovery and air heating.

The lead architect's office, Bögli Kramp, designed various optimization options, such as replacing the fabric sun protection with a higher wind class, slat blinds, replacing the windows and a type of canopy over the windows (fixed shading). Using thermal-energetic simulations of the existing building, a study was carried out to examine the existing variants for their potential for improvement and to look for new ways to optimize the indoor climate.

At the end of the project, a total of nine different variants and combinations of variants were simulated in two classrooms. A change to more efficient LED lighting, better night-time cooling and more wind-resistant sun protection showed the highest possible potential for improvement at low cost.

Added value

• Analysis of the indoor climate under a wide range of boundary conditions
• Variant and optimization study using computer simulations
• Identifying the potential for improvement of measures
• Transparent and data-supported results

Services

• Dynamic building simulation
  Dynamic building simulations take into account relevant factors such as location, shading, building physics, use and building services systems and represent a digital model of reality.
  
  
• Room utilization profile, internal heat loads
  Knowing how the internal heat loads and time profiles are composed is crucial in order to obtain accurate simulation results. In the GYB, the lighting waste heat is very high due to old halogen lights and could be significantly reduced with LED replacements.
  
  
• Site-specific wind analysis
  Particular attention was paid to controlling the solar shading. To ensure that the solar shading behaves as it would on site, the wind gust weather data from Payerne was adapted to the location of the school and used as a control limit value for the solar shading.
  
  
• Evaluation of the simulation results
  In accordance with SIA180, the perceived or room air temperature should not exceed the upper limit curve in rooms where the windows can be opened and people adjust their clothing seasonally. In the optimized variant, the indoor climate could be massively improved.

• Relationship between outside air and indoor air temperature
  The graph above shows the relationship between outdoor air temperature and indoor air temperature. The regression line characterizes the relationship between the two variables and enables a visual comparison between the variants. The flatter the line, the better the thermal performance of the variant.

• Transparent data basis
  A clear fact sheet compares all variants with each other and enables the best variant for the project to be determined. In this case, LED lighting, more wind-resistant solar shading and an overhaul of the mechanical ventilation were chosen.

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