Historic preservation and photovoltaics – a sustainable pair
In May 2024, the listed house in Fürschwendi, Eggersriet (SG) was equipped with a customised LEVEL roof-integrated solar system from Megasol – a breakthrough after seven years of intensive negotiations with the office for the protection of historical monuments of the Canton of St. Gallen. Thanks to the close cooperation between the installation company and Megasol, a solution was developed that convinced both the municipality and the cantonal office for the protection of historical monuments. This project sets a new standard and serves as a model for the authorisation procedure introduced in the canton of St. Gallen in autumn 2023, which should make similar projects easier in the future.
A new PV system was needed
Karl Büchler, the owner of the house in Fürschwendi, had wanted to replace his aging solar thermal system with a larger and more efficient PV system since 2017. After all, there was now a higher demand for solar energy due to, among other things, an air-to-water heat pump and an electric car. The old system was installed on the roof where it was visible to everyone. So it seemed reasonable to assume that approval for a new system would not be a problem. That was far from the truth! The preservation order was interpreted differently. This resulted in a number of challenges regarding the approval. The hamlet of Fürschwendi is one of Switzerland's nationally significant heritage sites worthy of protection. This means, for example, that traditional materials must be used for renovations, including the roof renovation.
before
after
Objections of the preservation order
The old solar system was a rooftop installation for solar thermal energy. A proposed new, larger PV system would have significantly altered the appearance of the roof, which is covered with grey Eternit shingles, making it a conspicuous foreign element. The initial building applications for the new roof-mounted solar system were therefore rejected by the preservation authority, as it would have excessively disrupted the historical aesthetic of the listed ensemble. ‘First of all, the color didn't match, then the size of the planned PV system. It was difficult to find a compromise with the heritage protection authorities,’ says Karl Büchler in a report by Schweiz aktuell im SRF.
It was only a cantonal amendment to the law on the protection of historical monuments in 2022 that enabled progress to be made in the approvals process. According to the new approval procedure, the roof landscapes worthy of protection in the canton of St. Gallen are categorised using a traffic light system in red, orange and green. The hamlet of Fürschwendi is in an orange area and is therefore one of the roof landscapes with high value. On this basis, roof-mounted systems will be possible here in the future, although the preservation order still has a say.
In 2023, Karl Büchler submitted a new application for approval of a solar installation. This was again rejected. However, the preservation order allowed for the application to be reconsidered if a compatible solution were found. This should allow the PV system to blend in better with the appearance of the historic roofs.
The solution
Karl Streule, managing director of Streule+Alder AG, took on this challenge. He had not only planned the project together with the client, but had also been involved in the negotiations with the office for the preservation of historical monuments from the outset. He was familiar with the arguments and reservations. He turned to his partner company Megasol that he had been working successfully with them for years and knew from this experience that he would find not only the right modules for his customers but also ideal support from a partner in his search for a solution.
‘The preservation authorities were sceptical about installing a photovoltaic system on a listed building,’ explains Karl Streule, managing director of Streule+Adler AG. ’But in the end, we were able to convince them with Megasol's custom-made, non-reflective modules. They blend harmoniously into the overall historical picture.’
He was able to discuss the requirements of the preservation order with his contacts and look for a solution for the implementation. After all, Megasol had the relevant experience, having already installed Megasol solar roofs on a number of historical buildings in recent years. In the case of the house in Fürschwendi, the roof-integrated solar system LEVEL proved to be the solution.
LEVEL impresses the heritage protection authorities
To ensure that the modules of the LEVEL roof-integrated solar system in ‘Full Black’ blend in better with the matt-grey Eternit shingles, they were matted in a special process. This meant that, as ‘ZeroReflect’, they were not only low-reflective and low-dazzle, but the dark, matt grey tone took on the visual characteristics of the Eternit shingle roof and met the requirements of the preservation order. Karl Streule personally presented the samples to the relevant people in the municipality and the heritage protection agency, impressing them with the product. The installation in Fürschwendi also served as a showcase project for the newly introduced approval process in the canton of St. Gallen, impressing with its harmonious integration.
Installation of the PV system
Shortly afterwards, installation work began on the south-east facing part of the roof. The small, old system was dismantled over an area of around 97 m². In addition, some of the Eternit shingles were removed. The roof was covered with the LEVEL roof-integrated solar system in this area. On the upper part of the roof, a total of 40 PV modules were installed at a roof pitch of 40° over an area of around 69 m², and a further 16 PV modules were installed at a pitch of 35° over an area of around 28 m². Four fall protection devices and a final snow guard were added to the 56 modules over the entire length of the system. The total yield forecast for the system is 16,928 kWh. The installation itself was carried out quickly: mounting hooks and support plates were mounted on the battens, the sealing rails were screwed on and the modules were inserted. In this way, experienced installers can install 10 m² per person-hour.
Technical data of the solar energy system
- Installed module capacity: 19.04 kWp
- Module type: LEVEL solar roof with ‘ZeroReflect’ technology
- Number of modules: 56 glass-glass modules, specially frosted for low-glare and low-reflection surfaces
- Total roof area of the PV system: 96.65 m²
- Yield forecast: 16,928 kWh/year
- Fire protection: Broof (t1) according to DIN EN 13501-5
- Hail protection class: Class 5 (50 mm grain size)
- Additional elements: Four fall protection devices and a snow guard for protection.
Do you have a listed building?
The photovoltaic system could be harmoniously integrated into the historical ensemble and sets new standards for listed buildings that are to generate sustainable electricity. We at Megasol offer customised solutions for historical buildings that meet the highest aesthetic and technical requirements. Contact us – together we will find the perfect solution for your property.
