The City of Stockholm has carried out innovative energy efficiency renovation of four fourteen-floor buildings and two four-floor buildings built in 1961 (324 apartments). Similar to other older buildings, these had problems with thermal bridges and climate shell insulation. A significant amount of heat and energy was lost in the existing energy installations in these buildings, due to long distances of poorly insulated pipes for heating and water, as well as the absence of heat recovery systems.
The climate shell refurbishment consisted of a package of innovative technologies:
- Additional insulation of 80 mm on building façade and 200 mm on basement walls.
- New type of roof construction with added insulation.
- New four glass windows with U-value 0,7 W/(m2K).
- Separate heat exchanger in every building for district- /geothermal heating.
- Heat pumps recovering heat from the exhaust air and transmitting it to produce heat and hot water
- Wastewater heat exchange system to preheat fresh water
- Installation of “pipe in pipe” system to reduce hot water circulation losses
- Water-saving tap water fixtures to reduce water consumption
- Electricity saving measures, including low energy lighting fixtures for common spaces and modern and more effective elevators
- Renewable energy installation: photovoltaic cells to produce electricity for the building use.
In addition to the above innovative technologies implemented, the project also equipped several apartments with smart home energy visualization applications in the form of a screen connected to smart plugs, to monitor energy consumption in real-time. This raised the tenants’ awareness of their own energy consumption, aiming to encourage a more sustainable way of life.
The renovation was made by the housing company Stockholmshem, a private company partially owned by the City of Stockholm, who are the owners of the apartment blocks in question. Stockholmshem took on most of the costs., while certain sections of the renovation, such as the climate shell refurbishment were part of GrowSmarter and thus supported by EU-funding through the Horizon 2020 Initiative.
What are the CO2 reduction goals and achievements?
CO2 Reductions: The ambitious aims set in the GrowSmarter project are to achieve 60% of energy saving and 60% of CO2 emission reduction. This is to be achieved through, among other things, shell refurbishment, energy efficiency measures on buildings and in apartment level, photovoltaics on the roof of the taller buildings and sedum roofs on the lower buildings.
The baseline for heating, cooling and electric energy has been obtained through measurement of annual energy demand (kWh/m2) corrected for ambient conditions before measures have been implemented. The annual performance is displayed as energy signatures, highlighting any difference between the two scenarios. The emissions data source is established from official authorities and used throughout the evaluation period of baseline and evaluation of conducted measures. The consumed energy mix has been established and used throughout the evaluation period of baseline and evaluation of conducted measures.
Expected savings compared with baseline:
- • CO2 emission reduction: 54%
- • Space heating and domestic hot water use reduction: 54%
- • Purchased electricity reduction: -17%
- • Total energy consumption reduction: 50%
Air Quality: The goal is to achieve a 60 % decrease in controlled emissions from transport in the project through mobility measures connected to the refurbishment of the buildings (such as electric car pool, e-bike pool and e-cargo bike pool). By incorporating sedum roofing, not only is there better insulation, less energy use is needed. The vegetation on the roof is an efficient air cleanser. It also creates a favorable environment for birds and insects with a positive impact on biodiversity.
This model of energy efficiency climate shell refurbishment can be replicated as a whole or in parts. This pilot project sets a good example for other locations, as it includes systems for district heating for five of the buildings, but also a system for geothermal heating for one of them. These systems can also be used for cooling. In Sweden, an ongoing research project at KTH Royal Institute of Technology has mapped existing buildings by type, energy performance, insulation level, and type of ventilation system, amongst other aspects. For Stockholm, the potential for a full-scale implementation of this pilot energy efficiency retrofit will be informed by this database.
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