Photo: Staffan Bolminger

Construction of Hamnhuset began in 2006. It consists of two apartment buildings of four to five stories surrounding a sheltered courtyard, and contain a total of 115 rental apartments, the largest of which consist of four rooms and kitchen. The building attracted great interest from the public when they were built. The apartments were let very quickly and the tenants moved in during summer 2008. One of the apartments has been kept as demonstration apartment to show people how the building works.

The buildings have been constructed to minimize cold bridges in the exterior walls. This means that the insulation is nine centimeters thicker than buildings constructed in the conventional way. Hamnhuset also has more insulation between interior concrete walls and the facade.

There are no radiators in Hamnhuset. A heat exchanger is used to warm fresh air from outside using air that is extracted from the building. On very cold days, heating is supplemented by district heating through the supply air ventilation system.

Hamnhuset uses 60 kilowatt hours per square meter and year for heating, electricity and hot water (the current Swedish building standard prescribes a maximum of 100 kilowatt hours per square meter and year). Of these 60 kilowatt hours, 18 are used for heating, 13 for hot water, and 29 for electricity.

Hamnhuset also has solar panels on the roof that provide half the energy needed to heat the hot water used each year.

Hamnhuset has a waste extraction plant with source separation into three different fractions. In practical terms, the waste extraction plant means that garbage trucks do not need to enter the area, but collect the waste at a point just outside. In every staircase, there is a recycling room where tenants can place cardboard, plastic, glass, and batteries.

Bengt Dahlgren AB (The company is located in Region Västra Götaland)

• Hamnhuset has 70% lower emissions of carbon dioxide compared to a building constructed with conventional technology.
• Passive housing uses only 25% of the energy for heating that conventional buildings use.
• The solar panels that heat the tap water in the summer provide 125,000 kilowatt hours a year. This is equivalent to half the energy needed to heat the tap water for a year.
• Passive housing makes you less vulnerable to increases in energy prices.
• It is not more expensive to own and operate an energy-efficient, environmentally friendly, comfortable building. On the contrary. In the long term it is cheaper.
• The investment is 2.5% higher to begin with. But the total cost is lower after a year.
• Constructing energy-efficient housing reduces the total cost by 32 SEK per square meter. This means a cost reduction of 370,000 SEK over the first year. The saving will probably be even greater in the long term since energy prices are expected to increase.
• With a costing interest of 7% and an annual increase in energy prices of 2% above index, ROI is 0.2% higher than for a building constructed with conventional technology.