Retrofit of the castle De Merode in Belgium – Preserving history while protecting the future

“It’s useless to try to maintain historial heritage if it’s to destroy the future,” says Simon de Merode, manager of the Castle de Merode. For him, the responsibility of maintaining a building with historical significance goes hand in hand with minimizing its environmental impact.

The recent renovation of the Castle de Merode—a historic Belgian landmark dating back to the 14th century—faced significant challenges. These included adapting a heating system to work with existing radiators, meeting strict aesthetic and material standards, and heating the castle’s vast interior spaces. Yet, despite the hurdles, this project demonstrates the exceptional capabilities of Ecoforest heat pumps in even the most challenging environments. So much so that it earned recognition from the Belgian Federation of Energy Transition.

Innovative Aquathermy: Harnessing Water to Generate Heat

Given the castle’s historical status, traditional air-to-water solutions were not an option, and boreholes were unfeasible due to the surrounding moat. The innovative solution? Aquathermy—utilizing heat collectors specifically designed for water bodies. This cutting-edge technology extracts up to 90 kW of heat from the castle’s 5000 m³ moat. The project was expertly managed by Extraqt, an engineering firm specializing in aquathermy, in collaboration with Eco-Techn.

A digital twin was created to simulate the water’s cooling process during heat extraction. Through a closed-loop system and a 100-meter pipe network, this heat is transferred to the castle’s heat pump. Remarkably, the system operates efficiently year-round, from the mild summer months to the frigid winter days when the water temperature barely rises above freezing.

Balancing Tradition and Innovation

The installation team determined that heating the castle’s rooms would be achievable with water temperatures of 45-50°C, as long as outdoor temperatures remained above freezing and the moat didn’t freeze over. To ensure reliability, the existing gas system was hybridized with the high-power heat pump, providing additional heat during extremely cold days.

The castle’s existing cogeneration system also continues to produce electricity and maintain water temperatures above 50°C. Supplementing the system, solar panels installed in a nearby shed contribute to the electricity supply. Despite the complexity of this renovation and the reliance on conventional radiators, the installation achieves an impressive SCOP of 3.2. This results in a 50% reduction in CO2 emissions compared to the previous system, significantly lowering the environmental impact of preserving this historic estate. This extraordinary results along with the project challenges made it the runner-up project in the high-power cathegory in the ecoAWARDS organised by Ecoforest to highlight the best heat pump installations.