A zero-energy refurbishment solution for retrofitting residential apartment buildings by applying has been developed by Dutch researchers at TU Delft university.
The concept is an integrated, prefabricated and lightweight building envelope that acts as a building’s second skin. With this low-carbon solution, existing buildings can be easily upgraded and meet eco-friendly building requirements.
The solution been developed under Building Technology Accelerator programme of the European Institute of Innovation & Technology’s (EIT) Climate-KIC project.
The “2ndSkin” project brings together different stakeholders of the building industry, aiming at integrating their expertise and objectives into an innovative building retrofitting concept that achieves zero energy use of a dwelling, while offering up-scaling possibilities.
The focus of the 2ndSkin project is the low-rise, multi-family residential buildings, accessed by separate stairwells per 6-8 apartments. This type of building represents about 300 000 houses.
Nevertheless, the concept of the renovation can be applicable in apartment blocks of other than the post-war period, increasing significantly the impact of the solution with a potential target of 875.000 apartment blocks in the Netherlands.
Existing buildings can easily be upgraded at a low cost by adding a second skin to their façade. When retrofitting the building, tenants will not have to relocate during construction activities. The envelope is easily installed within a short period of time.
By renovating existing building stock such as multi-family postwar buildings, energy consumption and CO2 emissions can be reduced significantly.
To meet the requirement of zero-energy consumption, the solution consists of three basic elements:
Increase the thermal resistance of the building envelope, including walls, windows and roof, installing heat recovery ventilation, to reduce energy demand for heating while providing adequate indoor air quality (IAQ), and use photovoltaic (PV) panels to generate energy.
The key advantages are:
A simple payback analysis, balancing only the initial investment required for the renovation against the potential energy savings resulting from it, shows that a complete 2ndSkin renovation would have a payback time of just over 25 years, or a simple average rate of return of 4% per year.
The overall solution can, hence, be an answer to the need for upgrade the building stock to provide comfort and low energy demand, with minimum occupants disturbance. The construction system is based on prefabrication, maintaining still some degree of flexibility, such as different type and size of windows or different cladding material. In this way, the concept aims at higher acceptability and, thus, applicability.