One of these pilot projects is Valla Torg, which encompasses the energetic renovation of 12 apartment buildings in Astra, a quickly growing district in south Stockholm. Altogether 302 apartments distributed over four high-rises and two apartment tracts are currently undergoing refurbishment – with the goal of achieving energy savings of 60%. The first phase alone reduced consumption from 154 kWh/m² to 61 kWh/m². Here, it was important to the planners that they preserve the exterior identity of the sleek 1960s-era structures. Façade insulation 80 mm in thickness was installed; the windows have been replaced with new, two-part models, which call earlier box windows to mind. Two panes of insulating glass, which sit in narrow frames (retro look) achieve a U-value of 0.7 W(m²K).
An exhaust air-heat pump, a system to use grey water and water-saving fixtures have all been installed, rounding out the common ways to save energy. However, the garbage disposal system is something completely new. It goes without saying that the garbage is separated and placed in sacks of different colours. A chute swallows the sacks. But then it gets smart: a vacuum system shoots the sack into the appropriate subterranean disposal system. Once there it is recycled, composed or fed into the system’s central thermal power station. The street lighting is just as smart. It no longer stays on all night; its motion sensors detect pedestrians or cyclists and light the lamps only when people move.
Even in the apartments, sensors record all the data required to precisely determine users’ behaviour in order to derive further methods for saving energy. For instance, the humidity in the bathrooms is measured, as are the room temperature and when the light is on in which room. Data involving the flow of pedestrians, cyclists and motorists are compiled as well. A car and bike sharing system is already available, digital of course, and under smart control.
The success of these digitally controlled energy-saving solutions will not be known until the long-term test is complete. As far back as the 1990s, the city set a goal of no longer requiring fossil fuels by 2040. May this research project contribute to achieving that ambitious aim.