Case Study: Lågenergihuset

Short Description

Bostads AB Poseidon has a large number of apartment buildings of similar type which were built between 1967 and 1971. The buildings are in great need of renovation. To ensure that the renovation is carried out in the best way possible the company initiated a renovation pilot study that focused on a house built in 1971 with 16 apartments in order to gain experience for future renovations.

A thorough feasibility study was conducted in the spring 2008. The feasibility study was conducted by a project group which included the contractors. A reference group was also formed to support the project group in more complex issues and standpoints. Except from Bostads AB Poseidon employees the reference group also included a professor, a graduate student and the project manager The feasibility study focused on the conditions of the existing building which resulted in a number of technical renovation solutions. The various alternatives were then evaluated economically.

The renovation started in 2009 and was also completed that year.

Key Elements

Capacity Building

Participants in the project received an education of what project objective was to increase understanding.

Work with Residents

Information and housing advice for tenants that covered behavior differences living in a low energy house compared to a “normal house”.

Funding

The project has a return profit requirement of 6.25%.The building has a 50 year technical life. The renovation was equity financed.

Partnership Working

Bostads AB Poseidon collaborated with the Technical University of Blekinge and with Chalmers University of Technology as a graduate student and professor were included in the reference group.

Thermal Insulation

The building was fitted with 200 mm foam insulation, which also sought to minimize the impact of thermal bridged.

Air Tightness

The design requirement was 0.3 l / s, m ^ 2 at 50 Pa, a requirement the building passes with margin.

Windows and Shading

All windows were replaced with low-energy windows with a 0.9 U-value.

Ventilation

A FTX system was installed.

Heating and Hot Water

Individual hot water metering was introduced. The house is connected to district heating net.

Electricity Saving Products

All lights are compact fluorescent lamps, low energy major appliances were installed and ventilation was optimized to use as little electricity as possible.

Water Saving

Low-flow fixtures were installed.

Main Results

The project will meet the target set: an energy reduction from 178 kWh to 60 kWh.
Key to success was the experience of and the interaction between the project team and reference group. In general, participants in the project were very commitment to the task.

Lessons learned

Most importantly, lessons have been learned on how renovations on these types of buildings can be conducted.  Furthermore, understandings on the economic challenges facing the company have been increased.

Bostads AB Poseidon strongly recommends other companies that are about to undertake similar projects to carefully review their own building stock potential and to perform field trips to others who have completed similar projects.

There are no quick solutions in this type of renovation; each building has its own basic conditions. Furthermore, it is important to avoid poor workmanship.