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CO2 payback of renovation of Torenflat social apartments in Zeist, the Netherlands

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To illustrate how the energy performance of existing buildings can be upgraded, the European Aluminium Association compiled the following case study.

The Torenflat (high-rise apartment block) contains 484 apartments on central corridors on 19 residential levels. One of the important objectives of this huge renovation operation, which was carried out entirely whilst people were living in the building, was to eliminate all the thermal bridges of the complex. This was achieved in 2008 by enclosing the entire building in a ‘warm jacket’, a light thermal skin comprised of fully prefabricated aluminium façade units that could be fixed onto the existing structure. Each apartment was given a new skin in one working day. By enclosing the building in this way, the thermal performance of the building was dramatically improved: the energy performance of the building has been improved by three categories according to the Dutch building energy labeling system. This project combined minimal investment with maximum social, economic and environmental benefits, and won the European Aluminium in Renovation Award 2009 in the residential category. An independent expert was involved in order to secure the scientific validity and technical quality of the above calculations.

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Acronym of the case

Torernflat Zeist renovation

Lessons learnt

A simplified life cycle assessment focused on greenhouse gases concluded a CO2 payback period of 13 years when recycling is disregarded and a payback period of 4.4 years when end-of-life recycling is taken into consideration. The use phase data were modelled by Senter Novem, an agency of the Dutch Ministry of Economic Affairs. The production phase was modelled on the basis of the material composition. The end-of-life phase was calculated as two scenarios, i.e. with and without end-of-life recycling. The CO2 payback period is fairly long in this case due to the very ambitious scope of the renovation project, which required a new envelope skin for a large fraction of the building.

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