REHAU Brings Rosslyn Castle into the 21st Century

Situated just nine miles south of Edinburgh, Rosslyn Castle is a true hidden gem among Scotland’s many historic sites. Though not as widely known as the capital’s fortress, Rosslyn Castle is a stunning sight all the same, offering panoramic views over the River Esk below from its promontory on the cliffs of Roslin Glen.

Location	Scotland
Contractor	Lothian Heating
Year	2025
Product	Underfloor heating

Fortifications have stood on the site since the 14^th century, and the stronghold has survived numerous fires and military campaigns over the centuries, though today the castle serves an altogether different purpose. Following a period of restoration instigated by the Earl and Countess of Rosslyn, the fortress’ primary function changed over to that of holiday accommodation in 1985.

Heating Up History

After nearly 40 years serving holidaymakers, the site’s owners decided that another restoration project would be necessary in order to successfully bring the Category A listed building into the 21^st century. Commencing in 2022, the ambitious £4 million repair and restoration programme planned to fit the castle’s great hall and tower with a permanent roof for the first time since 1650, while also ensuring that the entire site was Net Zero ready.

Heating was set to be provided by six air source heat pump (ASHP) systems, which would be located in the second level of the castle’s vaults. This would help reduce the impact of any noise within both the castle and the glen below, while the thermal mass of the vaults would help maintain efficiency during cold weather.

James Cameron, Associate Director of electrical consultants Harley Haddow, explained: “The installation of six ASHPs would allow the site to transition from fossil fuels to entirely renewable means, with the inclusion of four large thermal stores helping to maximise efficiency and provide additional resilience.
“This was estimated to reduce the building’s heat and hot water consumption by 67% compared to the previous system, saving over 17 tonnes of CO₂ every year. We believe that this may be the oldest building in the world using ASHPs.”

Navigating the Past

Heat and hot water was set to be distributed around the building via a combination of underfloor heating (UFH) and radiator circuits. However, working within the confines of such a historic building would naturally invite its own challenges that required careful consideration, which is where REHAU was called upon to assist with the specification and delivery of the heating system.

Scott McDonald, Area Sales Manager at REHAU, explained: “From the moment we were brought on board, it was apparent that this was going to be a project with an extremely unique set of challenges. Fitting a heritage site with a modern heating system always requires a great deal of planning, and I don’t think any site exemplifies this more than Rosslyn Castle. However, through a combination of our own technical expertise and that of Harley Haddow, we were able to come up with an ingenious solution.”

REHAU’s UFH would be selected for its ability to evenly heat the space, which was a crucial consideration for large open areas such as Rosslyn Castle’s great hall. Moreover, the use of an UFH system would also allow the building to benefit from energy-efficient heating without compromising its historic aesthetic. The installation would be completed using a combination of diffusion plates, which replaced the original floorboards, and a screed rail system, depending on the available space within individual rooms of the castle.

For the radiator circuits, the castle’s historic walls and floors provided minimal room for manoeuvre, while minimising damage to the listed building’s fabric was also critical. Here, REHAU’s RAUTITAN MLCP would prove paramount to overcoming this challenge while still ensuring a high-quality installation.

The pipework’s innate flexibility would allow it to be easily bent by hand into the required shape and installed within the building’s narrow channels. RAUTITAN’s proven compression sleeve jointing system also negated the need for any hot works that would have posed a threat to the building’s fabric, and would have also been difficult to complete in the space provided. Lastly, RAUTITAN’s signature lack of O-rings also guaranteed that the pipework would remain leak-proof once installed, offering maximum peace of mind to both installers Lothian Heating, and the castle’s owners.

Angus Liston, Director at Lothian Heating, said: “Getting a building such as Rosslyn Castle Net Zero ready is no mean feat, but has been made possible through the hard work and collaboration of REHAU, Harley Haddow, and our own team. Overhauling the castle’s outdated heating system was a key element in the owners’ latest restoration project, and has gone a long way to providing the site with a new lease of life for a whole new generation of visitors to enjoy”

Find out more about Harley Haddow.

Find out more about Lothian Heating.

Find out more about REHAU’s underfloor heating and RAUTITAN MLCP.