Aarhus City Council needs to extend its Building and Planning administration and will, in partnership with ALECTIA, add an extension in the form of a new low-energy office block.

Aarhus City Council has a target to become CO2-neutral by 2030. As buildings represent 30-40 percent of overall energy consumption, a targeted effort will be required to reduce energy consumption in both new and existing buildings.

ALECTIA, C.F. Møller and Aarhus City Council’s Property Administration are to build a new extension to the property on Kalkværksvej 10. The extension will be built as a low-energy office block with an area of approx. 1,600 m² distributed across six floors and one technical floor.

ALECTIA will help design the climate profile in the new building in partnership with the architects. The building's energy architecture is reflected, for example, in the design of the frontage. In the south and east-facing facades, solar cells and solar walls will be placed to create a live interplay between the sky-facing panels, glass sections and the integration of the solar walls in the natural stone facades.

Low-energy office block with “passive house” features
Aarhus City Council’s energy criteria are based on a wish to reduce energy consumption for heating to a passive house level, which corresponds to 15 kWh/m² per year. The new building will also be a low-energy Class 1. The building is to be completed by the end of 2010.

Energy measures in the office block
The following means were used to reduce the above energy consumption:

• SolarWall/solarCooling. An air collector has been located on the facade. The job of the air collector is to catch energy from the sun, after which the heated air is used in the building’s climate system. In the summer, the heated air is used in the cooling process, supplemented by district heating if required, and in winter the heated air is blown in to reduce the need for district heating.
• Phase-changing materials. In south-facing rooms, the building’s heat accumulation abilities are supplemented by phase-changing materials. 
• Vacuum insulation. In closed facade sections, vacuum insulation is used to improve the building’s insulation capabilities and to optimise the architectural design.
• Low-energy lighting. Energy-efficient light fittings are used throughout. In hallways and secondary rooms, LED fittings are used.
• Air tightness. The air tightness in the facade constructions is 0.6 h-1. This means that the building is approximately three times as airtight a building as required by Danish Building Regulations. It helps to ensure that heating is used optimally and does not escape through the facade.
• Solar cells. Solar cells are integrated in the south-facing facade.