Low-energy office building

The design of the new office building of Energinet.dk has been based on three overall environmental objectives:

• Local disposal of rainwater (LAR) resulting in a reduced load on the sewage system and reduced water consumption.
• Making use exclusively of materials that ensure a good indoor climate, small environmental impact and a minimum of maintenance.
• Low energy consumption and reduction of CO2 emissions.

Henning Larsen Architects has designed a low-energy building solely by means of optimizing the design and an geometry - resulting in an office building in the lowest energy class possible. The building has an energy consumption of only 47,7 kWh/m2 a year. Incorporating solar panels, ground water cooling and heat pumps in the project would further reduce the annual energy consumption to only 35 kWh/m2. The building meets the requirements for low-energy class 1 according to Danish building regulations without the use of energy producing technologies.

The design is based on the integrated energy design concept where the building is designed to achieve the lowest energy class possible - and thus the lowest possible maintenance and operation costs.

In order to reduce the energy consumption of the building, the design team has focused on:

Shape and orientation:. A compact building (large volume compared to surface area) reduces the heat loss and use of materials.

Functional positioning:. The energy consumption can be reduced significantly by means of a proper positioning of the various functions of the building. Permanent workstations are placed to the north-west and north-east to avoid overheating and blinding.

Daylight optimization:. By testing different daylight scenarios, the use of light and heat from the sun is optimised and the use of artificial lighting is reduced. Tailoring the light to the specific needs further optimises the use of artificial lighting. In the design process, light simulations have been applied to optimise the design and reduce the energy consumption for artificial lighting and cooling.

In the design process, a comfortable inflow of daylight has been ensured by means of the following:
• Permanent sunlight protection on the facades to avoid a direct inflow of daylight and overheating.
• Indirect inflow of daylight from overhead lights in the atrium.
• Direct sunlight from the west in summer in the cafeteria and conference rooms. During the rest of the year, the rooms are in shadow.
The offices feature three-layer low-energy windows and, in some places, north-facing overhead lights. The offices only have direct sun from the west in summer. For the rest of the year, the rooms are in shadow.

The building has a green roof serving several sustainable purposes: It reduces the load on the public sewage system by means of slow percolation and evaporation. In addition, the collected rainwater is used for flushing the toilets and watering the garden, which contributes to reducing the overall energy consumption for cooling.