Background and Project Content

The research project "Broad-Based Testing of Energy-Efficient Demonstration Buildings with Thermally Activated Building Components" was the first to systematically investigate a wide range of new and renovated buildings with thermally activated building components across Austria as part of the "City of the Future" program. Sixteen buildings with diverse uses were examined – from single-family homes to production and office buildings. The aim was to identify the applications, performance, comfort effects, and optimization potential of thermally activated building components and to provide comparable, reliable data for future construction projects.

The selection of demonstrators focused on a high degree of diversity with regard to activated materials (concrete, solid wood, brick), surfaces (ceiling, wall, floor), building application, use (heating, cooling), building quality and age, as well as heating and cooling supply concepts.

A standardized measurement concept for recording energy and performance data, temperatures, flow rates, and, in the extended monitoring phase, operative temperatures according to ÖNORM EN 7730, was applied to all demonstrators. In addition, user surveys and expert interviews were conducted to gather subjective experiences, decision criteria, and operational aspects.

Based on energy and comfort-related evaluations, building-specific optimizations were derived. Finally, the results were aggregated and recommendations were formulated for the planning, design, and operation of future thermally activated buildings.

Results

The comprehensive study of thermally activated building components (TABs) in 16 Austrian demonstration buildings shows that the technology can be used efficiently in all building types – residential, educational, office, commercial, and industrial. TABs utilize the thermal mass of ceilings, floors, or walls for heat and cold distribution, thus replacing conventional heating and cooling systems. This reduces technical complexity, lowers life cycle costs, and enables draft-free, silent, and uniform room temperatures. While ceiling activations are primarily used in residential and office buildings, floor activations are frequently employed in production and storage facilities. New approaches, such as activated solid wood ceilings or the retrofitting of existing walls, expand the range of applications, particularly for renovations. The low required supply and return temperatures, as well as the thermal storage capacity, make TABs ideal for efficient operation with renewable energy sources such as heat pumps, solar thermal energy, photovoltaics, and free cooling.

Monitoring reveals wide ranges in heating and cooling energy consumption, but overall a low energy level. The systems operate stably with moderate temperature fluctuations and exhibit high storage capacities. Room temperature measurements confirm a very consistent comfort level, predominantly within comfort category II.

Interviews and user surveys demonstrate high acceptance: Approximately 85% are very satisfied with the temperature and comfort. While the system's inertia is noticed, it is rarely considered a problem. Planners emphasize advantages such as energy efficiency and low operating costs but point to higher coordination efforts and a lack of standardized control strategies.

Economically, BTA offers clear advantages: Despite higher initial costs, lower energy and maintenance costs lead to lower life cycle costs; savings of 15–40% are possible. Furthermore, the large storage mass offers considerable flexibility potential for utilizing variable electricity tariffs and integrating renewable energy sources. However, active coupling with electricity and heat networks is still limited due to regulatory hurdles and a lack of market mechanisms. Studies recommend dynamic tariffs, predictive regulations and aggregation models to strengthen system integration and to utilize the large storage potential of building components activated.

Conclusions and Recommendations

This study confirms that thermally activated building components (TABs) can be used efficiently in all building classes. This technology utilizes the thermal mass of ceilings, floors, or walls as an integrated heating and cooling system, enabling draft-free, uniform room temperature control with high energy efficiency. Due to low system temperatures, TABs are particularly suitable for operation with heat pumps, solar thermal systems, geothermal energy, and free cooling. In addition to concrete, solid wood ceilings and retrofit activation systems such as CEPA are increasingly being used in existing buildings. The measurements show typical flow temperatures of 29 °C (heating) and 19 °C (cooling) and low energy consumption (heating median 37.8 kWh/m²GFAa; cooling 11.5 kWh/m²GFAa). The buildings predominantly achieve high comfort categories with very stable room temperatures. The high storage capacity of the components also makes buildings effective thermal buffers in the energy system.

Early, integrated coordination of architecture, structural engineering, building physics, and building services are recommended for planning. Materials and components should be selected appropriately; ideally, concrete or activated wood for new buildings, and CEPA or similar systems for existing buildings. Design for low-temperature operation, predictive control strategies, and combination with renewable energy sources and free cooling increase efficiency and flexibility. Monitoring and quality assurance during the first year of operation ensure correct system function. Life cycle cost analyses show that, despite higher initial investments, significantly lower costs are incurred in the long term compared to conventional systems.

Policymakers and institutions should establish TABS as a strategic instrument for decarbonization and energy flexibility. This requires the recognition of dynamic storage capacity in energy performance certificates and funding programs, the introduction of variable electricity tariffs, and the development of flexibility markets. Standardized interfaces, norms, and quality assurance processes facilitate planning and system integration. Research, training, and knowledge transfer—for example, through competence networks or demonstration projects—must be expanded. At the same time, further development of digital infrastructure is needed, particularly smart meters and interoperable data interfaces. By more closely coupling electricity and heat networks and taking them into account in neighborhood concepts, component activation can become an important building block for a climate-neutral, resilient energy system.

Project management

AEE INTEC

Project or cooperation partners

• e7 Energie Markt Analyse GmbH
• hacon GmbH
• Interdisziplinäres Forschungszentrum für Technik, Arbeit und Kultur
• Fachhochschule Salzburg GmbH
• FIN – Future is Now

AEE INTEC
DI Walter Becke
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A-8200 Gleisdorf
Tel.: +43 (3112) 5886-231
E-Mail: w.becke@aee.at
Web: www.aee-intec.at