Solar VHF: Recovering energy to heat buildings using rear-ventilated façade elements

Solar-VHF focuses on the solar thermal activation of rear-ventilated façade systems. The façade cladding absorbs solar energy and ambient heat and transfers this energy as low-temperature heat to a heat pump system. The building envelope thus becomes a renewable heat source.

The project focuses on the following key research areas:

• Experimental investigations of six façade cladding materials which are tested and monitored at outdoor test rigs under real-world weather conditions.
• Simulation models are developed and validated using the measured thermal performance data of the façade systems.
• Integrated system concepts combining heat pumps, thermal storage, and control strategies are developed for residential buildings.
• Demonstration buildings in Pforzheim and Hanover are monitored to evaluate and demonstrate the practical feasibility of the concept.
• The combination of Solar-VHF technology with an ice-based thermal energy storage system is assessed as an additional system configuration.
• Practical design guidelines are developed in collaboration with the German Association Rear-Ventilated Façades (FVHF).

The project aims to demonstrate the practical feasibility of the system, particularly through the two demonstration buildings. In addition, the project findings are intended to provide a sound basis for decision-making in energy-efficient building design and to help reduce planning and investment risks.

The core project is largely completed. The research team has experimentally investigated the solar thermal activation of metal, glass, and concrete cladding materials on dedicated test façades. The resulting measurement data are being used, among other purposes, to validate façade simulation models. These models have subsequently been integrated into a simulation model of a multi-story residential building to identify the optimal system configuration for Solar-VHF applications, including heat pump, supplementary heat source, thermal storage capacities, and control system.

The demonstration buildings in Pforzheim and Hanover are currently in operation. Researchers at Fraunhofer IBP and ISFH are continuously monitoring both systems to verify the practical feasibility of Solar-VHF technology and to compare predicted thermal energy yields with measured performance data.

As part of a project extension, additional commercially relevant cladding materials, such as fiber cement panels, high-pressure laminate panels (HPL), and aluminum composite panels have been incorporated into the research project. Together with the façade materials already investigated during the core project, this expanded scope now covers a broad range of commonly used façade cladding systems.

Experimental investigations of these additional materials are currently being conducted at the Fraunhofer IBP outdoor test facility in Holzkirchen and at the ISFH technical center. In parallel, the project team is analyzing both Solar-VHF as stand-alone renewable heat source and hybrid system concepts combining Solar-VHF with ice-storage technology. In addition, the monitoring of the two demonstration sites is ongoing, accompanied by measures to optimize the system operation. In collaboration with the FVHF, the project team is also developing design guidelines to accelerate the transfer of knowledge into professional practice and support the implementation of Solar-VHF systems in the construction sector.

• Institute for Solar Energy Research Hameln (ISFH)
• Systea GmbH
• Clina Heiz- und Kühlelemente GmbH
• Konvortec GmbH
• Pforzheimer Bau und Grund GmbH
• Gundlach GmbH & Co. KG
• Trade Association for Building Materials and Components for Rear-Ventilated Curtain Facades (FVHF)
• Etex Germany Exteriors GmbH
• 3A Composites GmbH
• Trespa Deutschland GmbH