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Residential Retrofit assessment platform and demonstrations for near zero energy and CO2 emissions with optimum cost, health, comfort and environmental quality.

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Smart retrofitting toolbox for nearly zero-energy buildings

The renovation rate of Europe’s energy-inefficient building stock is around 1 % per year; it should be around 3 % to meet the goal of carbon neutrality by 2050. ReCO2ST offers decision-making support tools and tech to help get us there.

Climate Change and Environment icon Climate Change and Environment

According to the EU-supported ReCO2ST project based on Buildings Performance Institute Europe data, while 40 % of final energy use takes place in buildings, the majority of the European building stock is quite old. Some 80 % was built before 1990 and 40 % before 1960. As previous building regulations were either non-existent or more limited than today, energy use is typically inefficient. To boost renovation efforts, ReCO2ST has developed Retrofit Assessment Tools and a Business Model Kit for evaluating renovation options. “Being able to develop and rank renovation scenarios, while estimating costs, improves decision-making, making it possible to choose high-performance and cost-effective approaches tailored to individual projects,” explains Per Kvols Heiselberg, ReCO2ST project coordinator. The approach has already been successfully trialled in buildings in four countries.

Retrofit technologies

Innovative renovation technologies developed during the project were integrated by partners within four residential buildings in Denmark, Spain, Switzerland and the United Kingdom – customised according to their unique architectures and climates. “Our challenge was not only to refurbish for net zero emissions buildings but to do so cost-effectively, while also accommodating health, comfort and environment-friendly construction considerations,” remarks Heiselberg from Aalborg University, the project host. The ReCO2ST project focused on large building projects, typically apartments buildings. But with renovation timelines of typically 4-8 years from initial idea to completion, these preclude the full ReCO2ST approach from being tested within a single project, so ReCO2ST assessed the performance of single technologies at early adopter sites, then used simulation models to extrapolate for yearly estimations. The full range of retrofitting technologies assessed were: vacuum insulation panels, smart windows, nature-based solutions, concentrating photovoltaic, heating ventilation and air conditioning (HVAC) mechanical ventilation, HVAC + cooling evaporative Kit, cooling roof material and cooling evaporative units. The project found that smart windows, for example, fitted in buildings in Denmark, Switzerland and the United Kingdom showed a significant increase in inlet air temperature. Rooms with smart windows had an average energy saving of 39 %, while also improving indoor CO2 concentration and humidity. Taking the Danish demonstration building, by analysing 11 different renovation scenarios, alongside four different energy system solutions, the project concluded that careful selection can reduce primary energy demand by more than 60 %. A prototype approach used in the Swiss demonstration building showed a primary energy reduction of 70 %, with the investment returned in 19 years.

The support tools

Key to project success was being able to demonstrate the accuracy of the assessment tools and a favourable cost-benefit analysis. “Comparing predicted and actual energy savings indicated that our dynamic thermal model can be used with confidence when assessing planned interventions,” adds Heiselberg. “Additionally, on average, projected costs were close to reality, with actual costs about 5 % lower than our forecasts.” ReCO2ST also developed a business model toolkit and a financial module to help building owners launch energy conservation measures. The toolkit which provides crucial information about the management and financing of energy retrofit projects, was successfully tested at two early adopter sites. “Our approach benefits building owners, residents and society by helping increase the potential renovation rate of existing buildings to the 3 % needed to achieve carbon neutrality by 2050,” concludes Heiselberg. While the project team continue developing their tools, improving data collection and analysis as well as user-friendliness, partners also continue exploiting project results. Groupe E (website in French) and Estia, for example, are already using the project’s Retrofit Assessment Tools and the Business Model Kit in their services to customers.


ReCO2ST, retrofit, renovation, buildings, energy, carbon neutrality, simulation, thermal

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