Renovation of housing stock remains a common challenge

There is no doubt that the domestic housing stock has ecological and economic potential for renovation. Upgrade instead of demolition is the motto. However, the “climate factor housing stock” is complex overall, as the consultancy, planning and project management firm Drees & Sommer Austria knows.

Heat consumption in residential buildings accounts for about half of the energy consumption in Austria and about two thirds is covered by fossil fuels. Fossil energy sources account for just over three quarters of electricity consumption. Given the Green Deal, SDGs, and ESG, as well as the economic stability of housing portfolios, energy or engineering remediation measures are indispensable. “It must also be possible for users and owners to become part of the change of their own accord. This is not only about agreeing to renovation measures and the associated investments, but also about changes in their daily lives,” says Egon Gröller, who is responsible for the residential sector at Drees & Sommer Austria.

Technical solutions are available

Even if there is no one-size-fits-all recipe for refurbishment, but rather every existing building, its environment and its users must be considered individually, there is no shortage of technical solutions. Dr. Peter Holzer, managing partner of engineering firm P. Jung, refers to a feasibility study on eight residential buildings in Vienna. It examined six different technical solutions for phasing out existing gas heating: the use of a gas boiler centrally or decentrally with green gas, the conversion to district heating, central biomass, a central or decentralised air heat pump and a central or decentralised geothermal heat pump, as well as the use of direct or infrared heaters. The results of the study show that in each of the existing multi-storey buildings examined, different technical solutions for heating conversion made sense. The rough costs of the conversion were around 200 to 600 EUR/m² net, with the simultaneous conversion of all flats of a house. “Housing law issues relating to the conversion of heating systems are proving to be difficult and are still inadequately regulated. Beyond the building, questions of reasonableness also arise, for example with regard to noise emissions from heat pumps or the thermal use of public goods, e.g. by means of borehole heat exchangers in public spaces,” says Holzer. The investment associated with switching to new installations would pay for itself at the latest in the medium term. These systems have the greatest possible impact if the windows and walls of existing buildings are also renovated.

Digitisation is also helping to reduce energy consumption and CO2 emissions. In smart buildings, for example, processes and subsystems within a building can be coordinated and regulated in order to optimise both cooling and heating. Energy efficiency can also be increased by connecting smart buildings to each other via smart grids and exchanging energy as needed between buildings and surrounding urban infrastructure.

More alternative energy and less overall energy consumption

In order to phase out fossil fuels, an expansion of renewable energy sources is needed, says Holzer: “In the case of wind energy, an increase of a factor of three compared to today is possible, in the case of photovoltaics, even by a factor of eleven. In the case of hydropower, an additional 10 percent would be achievable, in the case of biomass, 20 percent.” Georg Stadlhofer, Managing Director of Drees & Sommer Austria, adds: “Despite these resources, however, only around half of the annual energy demand in existing residential buildings could be met. Also in view of the possible technical, energetic and structural renovation measures and the potential for efficiency enhancement made possible by digitalisation, there is still a gap here. In order to close this gap, it is necessary not only to expand renewable energies and increase the efficiency of the systems used, but also to reduce final consumption.”

Common will essential

In everyday life, this is all about simple things: switching off light sources that are not needed, keeping hot water running, and heating moderately in winter. For Paul Lensing of Generali Real Estate, energy efficiency also means rethinking individual requirements. Smaller apartments, designed for several people and thus more people per square metre, help to reduce energy consumption as well as running costs.  “Climate protection concerns us all, and renovation of existing buildings plays an important role in this respect. Investments in energy-efficient buildings ensure their future viability and always pay off. Users and owners can directly benefit from the benefits of upgrading apartments in their daily lives,” said Stadlhofer. Commenting on the current legal framework conditions, Lensing says: “The political will to renovate the housing stock in a climate-friendly manner is clearly discernible. However, the multitude of regulations and subsidies that exist side by side makes practical implementation sometimes challenging. Harmonisation of the respective laws at Land, Federal and EU level has further potential to achieve the climate targets set by 2050 and in Austria by 2040.”