COWI consultants used the IES Virtual Environment (IESVE) to carry out detailed performance analysis to ensure high performance and energy efficiency of Axeltorv Square.
Architect Lundgaard & Tranberg’s design for No. 2 Axeltorv Square, Copenhagen, is designed to bring life to the public square by opening up the city centre site to create a pedestrian thoroughfare.
The 42,000m2 landmark scheme, located next to the famous Tivoli Gardens amusement park, comprises five circular office towers. The towers relate to the surrounding architecture and vary in height from 28m to 61m. The towers are linked at high level by walkways spanning between the buildings and at street level by streets filled with shops and restaurants. From the ground floor, giant staircases lead the public up to a first floor garden. The towers’ upper floors will provide state-of-the-art offices for a law firm.
Consultant COWI worked in close collaboration with the architect to develop a low energy design scheme. Using IESVE they were able to make decisions on the best performance and energy conservation measures to implement. These included: a highly insulated facade, high performance glazing, energy efficient mechanical ventilation with heat recovery and the careful sizing and location of the windows on the towers’ curved facades to optimise the use of daylight while minimising the amount of energy used to keep the building cool.
The building’s city centre location and its complex geometry made it a challenge to ensure good levels of daylight throughout the building. In order to assess daylighting in the offices, the effect of solar gains and to develop an effective shading strategy COWI used the IESVE module SunCast. This enabled the consultant to analyse how the surrounding buildings shade the towers and how the towers shade each other.
“Based on the visualisations SunCast gave us, we were able to optimise the location of the tower’s windows,” says Michael Jørgensen, Architectural Engineer at COWI. “We did various studies to look at the impact of changing some of the window areas to see the impact on energy consumption”. COWI even developed a solution using vertical fins to provide an element shading on the circular facades to help further reduce cooling loads.
The energy modelling was undertaken using the IESVE ApacheSim module to simulate energy and indoor climate and heating and cooling loads. Initially COWI used the software to look at the impact of changing the window area on overall heating and cooling loads for the building. It then made a more detailed model of some of the offices to analyse the indoor climate to ensure the building would meet the latest thermal standards.
“Using IES-VE we were able do a whole building simulation and perform detailed analysis of energy, thermal indoor environment and daylight. Based on the model and its outputs we had good dialog with the architect and together developed an energy efficient design,”
Michael Jørgensen, Architectural Engineer, COWI