New multi-family house in Eschen – How dynamic building simulation saves on a second heat pump

Visualization of the MFH Eschen created by Schafhauser & Biedermann AG

During the construction of a new apartment building in Eschen (FL), conventional calculations threatened to lead to unnecessary additional costs: The structural analysis called for two heat pumps in cascade. Learn how we used dynamic building simulation to determine the actual heating requirements and save the client from oversizing the system.

Correctly sizing the heating system is a critical factor for the economic viability of a new building. If structural calculation methods are applied indiscriminately, this often leads to unnecessarily high investment and operating costs. Our client, Schafhauser & Biedermann AG, faced precisely this challenge with this project comprising seven apartments.

The starting point: Static calculation requires a complex cascade solution

The static heating load calculation according to SIA standard resulted in a power requirement of over 26 kW for the planned multi-family house.

The technical consequence of this calculation would have been complex: the planning of two air-to-water heat pumps in cascade. This would have had significant disadvantages for the project.

• Significantly higher investment costs for plant technology

• Increased complexity and space requirements in the technical room

• Potentially higher maintenance and operating costs over the entire life cycle

Due to the excellent building envelope, consisting of a prefabricated wooden facade with solid interior walls and combined with hemp blocks for additional thermal mass, this need had to be critically examined. Was the potential adequately considered in the structural calculations?

Energy model of the MFH Eschen, including modeling of surrounding shading objects

Our solution: Dynamic building simulation instead of static calculation

To clarify this question, BOP was commissioned to determine the effective heating load requirement using dynamic building simulation. The aim was to create a physically sound basis for decision-making that goes beyond static snapshots.

In close collaboration with the architectural firm and the HVAC specialist planning, we digitally modeled and analyzed the building:

• Precise representation of thermal inertia: The specific properties of the high-quality building envelope, and in particular the thermal mass of the hemp blocks, were incorporated into the model in detail using building physics principles. This is crucial for realistically representing peak loads.

  
  

• Consideration of topography: The simulation model incorporates the effective horizon and shading from neighboring buildings. This has a significant impact on solar gains, especially in topographically challenging locations.

  
  

• Detailed zone analysis: We not only simulated the relevant rooms, but considered the building holistically – including unheated zones such as the basement and stairwell.

  
  

• Variant studies: By simulating different variants with varying flow and room temperatures, we were able to transparently demonstrate to the HVAC planner which parameters influence the power requirement and to what extent.

The result: One heat pump is sufficient

The dynamic building simulation provided a clear result and refuted the assumptions of the static calculation:

• Effective heating power requirement: 19 kW (instead of 26 kW)

• Specific heating output: approx. 14 W/m²

The proof was there: A single air-to-water heat pump fully covers the heating needs of the apartment building, ensuring safe and comfortable heating even on cold days. Analysis of unheated areas such as the basement and stairwell also confirmed that temperatures in these rooms remain within a safe range year-round, within the insulation perimeter. This solid data provided the parties involved with the necessary planning certainty to consistently forgo heating in these areas.

The added value: reduced investment costs, increased efficiency

The decision to use simulation-based planning has paid off directly for the client. The savings from eliminating the second heat pump significantly outweigh the costs of the simulation.

The advantages at a glance:

• Direct cost savings: Elimination of the cascade solution and reduction of investment costs.

  
  

• Reduced complexity: Fewer components, simpler control technology and space savings in the technical center.

  
  

• Optimized operation: The system is correctly sized, cycles less frequently, and operates at its optimal point. This reduces energy consumption and maintenance requirements.

  
  

• Planning certainty: Architects and specialist planners received reliable data on temperature development and power requirements in all rooms.

This project exemplifies how those who rely on dynamic building simulation avoid expensive oversizing and create buildings that are technically, economically, and ecologically optimized.

Would you also like to save on investment costs and gain planning certainty in your next project?