New construction of two multi-family houses in the Canton of Aargau: Clarity regarding summer overheating in timber construction

3D energy model of the multi-family building

Modern timber construction is booming. It's sustainable, aesthetically pleasing, and creates a pleasant indoor climate. But what happens when tenants complain about overheating after moving in during the summer? Are these structural weaknesses or is it due to the occupants' behavior? This was precisely the challenge faced by the project team of two newly constructed apartment buildings in the Canton of Aargau. A precise, dynamic building simulation from BOP provided the necessary clarity and created a reliable factual basis for all parties involved.

The challenge: When tenants complain about overheating in the summer

In the Canton of Aargau, two high-quality apartment buildings were constructed using modern timber construction methods. The project was planned and realized together with the timber engineering specialists at Timbatec Holzbauingenieure AG. However, after commissioning and the first warm summer months, complaints arose from the residents, who complained about overheating in the living spaces during the summer.

This created a complex situation for the client and the specialist planning team. In timber construction, the issue of thermal mass is inherently more sensitive than in traditional solid construction, even if it is not the decisive factor. While the basic structural requirements for summer heat protection were reviewed and met during the planning phase, the implementation during the construction phase deviated from the plans, leaving the initial situation unclear. It had to be determined whether the basic structural requirements were still being met despite the deviations and whether unfavorable ventilation and shading practices by the occupants were the cause of the overheating. To avoid costly errors or legal disputes, an independent and thorough analysis of the completed project was necessary.

The BOP approach: Reality is digitally simulated exactly.

The planning team commissioned BOP to conduct a detailed review of the summer heat protection based on the completed project. Using a dynamic building simulation, we created a detailed model of the entire building.

To obtain a realistic representation, the BOP team proceeded as follows:

• Precise storage mass modeling: We precisely incorporated all specific component structures of the timber construction into the simulation model in order to accurately account for the thermal behavior of the storage mass.

• Detailed shading analysis: Our team recorded the complex environmental situation – including the neighboring buildings and the actual horizon.

• Real sun protection scenarios: In addition to fixed shading elements such as the wooden louvers in front of the balconies and windows, interior awnings were also accurately incorporated into the calculations.

The result: Building regulations met – user behavior decides.

The dynamic building simulation delivered a clear result: The proof showed that the basic structural requirements for summer heat protection could be met in all zones.

The cause of the temporary overheating was therefore not due to a deviation in design or incorrect planning, but to individual user behavior, such as insufficient night cooling via window ventilation or incorrect operation of the sun protection system.

Security for building owners and planners without expensive renovations

Thanks to dynamic building simulation by BOP, the building owner and specialist planners now have a sound basis for argumentation. Instead of undertaking complex and expensive structural modifications, those involved can now implement operational optimization measures based on the results and specifically inform tenants about the correct behavior.

Are you struggling with overheating and user complaints in existing buildings? We support building owners and specialist planners in gaining clarity: We check whether the basic building requirements are met and simulate concrete measures to provide you with a fact-based basis for decision-making.