Decarbonisation before thermal renovation?Assessing retrofit requirements for the transition to renewable heating

Project partner

• Scandens AG

Project description

As part of the ‘100 Projects Off Gas’ initiative, the project investigated the conditions under which multi-family buildings can be decarbonised without comprehensive thermal renovation. The aim was to identify realistic courses of action for a rapid transition to renewable heating systems (in particular heat pumps and district heating). This should facilitate the transition to renewable heating and support owners in their investment decisions.

The analysis was based on 30 real, typical residential buildings in Vienna, which were analysed in detail using Scandens simulation software. Heating requirements, heating load and flow temperature were calculated for the existing buildings and for various renovation scenarios. An interim target (decarbonisation with ≤ 55 °C flow temperature) and a target scenario (complete thermal renovation) were defined for each building.

The buildings were then assigned to seven typical cluster groups depending on whether thermal measures were necessary, advisable or unnecessary. The focus was on the technical capability to use low-temperature heating systems (low-temperature-ready). The results show that in many cases, decarbonisation is possible even without comprehensive renovation, particularly by optimising heat dissipation (e.g. radiator replacement, hydraulic balancing). In other cases, renovation is technically necessary. The key result was the development of a methodological basis for a decision tree. This provides owners with an initial assessment of the recommended measures based on a small amount of building data.

Key findings:

• Flow temperature as a key parameter: It is not the heating demand alone, but the required flow temperature that is decisive for heat pump suitability.
• Decarbonisation often possible without comprehensive renovation: In many cases, the required flow temperature can be achieved simply by technical measures relating to heat dissipation (e.g. radiator replacement, hydraulic balancing) can achieve the necessary flow temperature.
• Building clusters show systematic patterns: Two clusters with a total of 16 buildings are immediately LT-ready or close to it. Other clusters require targeted thermal measures to reduce the heating load.
• District heating areas enable simplified access to decarbonisation: Here, only building services adjustments are often necessary.

The study was commissioned by the Energy Planning Department of the City of Vienna as part of the ‘100 Projects to Get Off Gas’ initiative and supported by the Vienna Climate and Innovation Agency.

Click here to visit the Urban Innovation Vienna (UIV) website: https://urbaninnovation.at/