Passive school De Verdieping Heusden-Zolder

July 5, 2016


Client:  Gemeente Heusden-Zolder
Location:  Heusden-Zolder, Belgium
Period:  2013-2015
Size:  5.000 m²
Team:  THV A.A.Q. (Q-BUS Architectenbureau, Axis Engineering en ARAT), 3E


In April 2015, the passive school in Heusden-Zolder, called “De Verdieping”, was officially opened. This school, for which 3E was responsible for the energy concept and the passive certification, is one of the passive schools built within the Flemish passive school programme.

3E took up the challenge to find the most fitting energy concept, which allows compliance with the passive standards set for schools, reduces operational costs and meets the client’s requirements regarding comfort and flexibility.

  • Glazing is predominantly North oriented since solar gains on top of the (already high) internal gains would cause very high cooling loads.
  • Nevertheless the North orientation for most windows, active cooling was proposed for all class rooms. A detailed overheating analysis indicated that most classes required active cooling due to their specific function and the resulting high internal gains (computer class rooms, cooking class rooms,…). In addition to this, flexibility (to change class room functions in the future) and anticipating ongoing digitalisation (leading to an increase in internal gains) were important design requirements. This resulted in the choice of the design team to equip all classes with active cooling.
  • The thermal loads inside the building vary significantly as a consequence of the different functions and occupation profiles of the class rooms. Following the choice to implement active cooling, a heating and cooling concept was chosen that enables the exchange of heat and cold between different class rooms resulting in a high overall energy performance of the building.
  • Due to the typical dense occupation of class rooms, the resulting high humidity levels could lead to condensation in case of radiant ceiling panels or chilled beams. The design team therefore chose a fast-reacting air based emission system (compared to slower emission system options).
  • With regard to ventilation a cost-optimal solution was found by choosing for a semi-decentralised concept. The school is equipped with 10 separate ventilation groups with Variable Air Volume (VAV) control to take into account the fact that many class rooms will be empty at times when others are not. This allows limiting duct sizes and floor-to-floor heights, while avoiding an overshoot of ventilation groups to keep maintenance costs down.

The efficient HVAC-equipment, together with the passive school requirements and the choice for photovoltaic panels on the roof, enabled the creation of an NZEB-building, clearing the path for a long-term sustainable future for this school.