THE HOUSE AS A POWER SOURCE
Updated: 2 days ago
How the careful transformation of a historic ensemble can preserve its character while
preparing it for a future without fossil fuels.
What if an existing building could become part of the energy transition without losing what makes it worth preserving? At Wilhelminian Heritage, a late nineteenth-century townhouse and its historic timber-framed barn were transformed into a contemporary residential ensemble. The ambition was to retain their architectural identity while fundamentally rethinking how the buildings use and generate energy. Today, the ensemble is heated without fossil fuels and produces more electricity over the co
urse of a year than its total annual electrical demand. The result began not with technology, but with understanding the buildings.
Reading Before Replacing
Every existing building tells a story through its construction, materials and the changes made over time. Renovation begins by distinguishing what deserves to remain from what needs to change. At Wilhelminian Heritage, the townhouse and the historic timber-framed barn required different approaches. Their original structures, proportions and architectural character formed the starting point for the transformation. One of the most significant interventions was the removal of a later addition that had occupied the space between the two buildings. Its demolition restored the individual architectural presence of the townhouse and barn while creating something equally valuable: an open courtyard. This newly recovered outdoor space now accommodates parking, a terrace and planting, as well as the outdoor unit of the heat pump serving the building’s energy system. What was once built over has become a place that connects the two buildings without compromising their individual identities. Sometimes, the most meaningful intervention is not what we add, but what we choose to remove.
„Every existing building tells a story through its construction materials and the changes made over time.“
From Building Fabric to Energy System
Reducing energy demand was the first step. The roofs were insulated and renewed, the rear façade received external insulation, and cavities within the walls adjoining neighbouring buildings were filled with insulating material. The garage ceiling in the barn was also insulated. New windows and entrance doors further improved the building envelope. These interventions are largely invisible in the completed architecture, yet they are fundamental to its performance. They reduce heat loss and allow the energy systems to operate more efficiently. The technical transformation was therefore not conceived as a separate layer. It developed from the building itself.
New Technology, Existing Architecture
With the thermal envelope improved, the ensemble could be supplied by a heat pump instead of a fossil-fuel heating system. Photovoltaic panels on both roofs generate electricity for the buildings, including household use, heating, hot water and electric mobility. The challenge was to integrate these systems without allowing them to dominate the historic architecture. This required coordination between conservation, construction and building services — and an understanding that technical performance and architectural quality must be developed together.
What the Numbers Reveal
The energy balance demonstrates the impact of these combined decisions. In 2025, the photovoltaic system generated 11.40 MWh of electricity. Across the annual balance, this exceeds the ensemble’s total electrified energy demand by approximately 57%. The detailed figures are shown in the energy diagram above. This does not mean that the buildings are independent of the electricity grid. Generation and consumption occur at different times, making both grid imports and exports necessary. But it demonstrates how far an existing historic ensemble can be transformed through a coordinated approach to building fabric and energy technology.
„Preservation, in this sense, is not simply about maintaining the appearance of the past. It is about giving existing buildings the capacity to remain relevant.“
Beyond Preservation
The completed buildings retain their architectural identity. The townhouse continues to express its Wilhelminian character, while the restored barn remains recognisable as part of the site’s history. What has changed is how the ensemble performs. Preservation, in this sense, is not simply about maintaining the appearance of the past. It is about giving existing buildings the capacity to remain relevant. The most sustainable decision is not always to build something new. Sometimes, it begins by understanding what is already there — and recognising what it can become.
Today
„The most sustainable decision is not always to build something new. Sometimes, it begins by understanding what is already there — and recognising what it can become.“
Before
