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At the Cutting Edge

The use of innovative building practices sees a unique coastal property embrace a sustainable, sensitive and challenging design. 


Words by Lydia Paleschi


Perched on the coastal slopes of north Cornwall and overlooking the coastline leading to St Ives, lies Edge O’ Cliff. This multi-award-winning architectural marvel, designed by ARCO2 Architects and constructed by Umbazi Builders, is an impressive example of innovative and sustainable building practices in a location that is equally challenging and picturesque. 


Carbis Bay is celebrated for its beautiful sandy beach, clear waters, and scenic coastal views. Situated within an Area of Outstanding Natural Beauty, and close to a Site of Special Scientific Interest, it offers a unique blend of natural splendour and environmental importance, with the proximity of the South West Coast Path, enhancing its appeal. Edge O’ Cliff benefits from this exceptional location, providing a tranquil and scenic backdrop for a sustainable, luxury home.


The original house at Edge O’ Cliff was a three-bedroom wooden chalet constructed in the 1920s. A charming yet energy-inefficient structure, the property was also slowly slipping down the cliff towards the sea. Recognising the unrivalled location of the chalet, the decision was made to replace it with a new, modest three bedroomed house. With it being a locally significant, highly visible and environmentally sensitive site, it was crucial to create a new property with not only comfort, but also sustainability and aesthetic harmony in mind. 


With unique opportunities come unique challenges and the construction of Edge O’ Cliff was no exception. The site is accessible only via a steep, stepped, winding coastal footpath that crosses a pedestrian railway line, presenting a significant logistical challenge. The utilisation of conventional construction techniques was out of the question and there was no site access for vehicles or construction machinery. The only option was to ensure all building materials were small and light enough to be transported down the footpath by hand. 


Using innovation, determination and a significant dose of passion, ARCO2 and Umbazi embraced the challenge with a meticulous approach from the outset. Working together from the early design stage, they adopted a ‘stick-built’ twin wall timber frame construction method using locally felled Douglas fir. This method allowed for small pad foundations, which required a modest amount of excavation and reduced the need for concrete. Together, this minimised the environmental impact on the site and the surrounding landscape whilst also providing a solution to the logistical challenges. 



Deconstruction of the original chalet provided critical lessons in sustainability for both the design and the building teams, particularly when it came to the use of materials. Whilst the team salvaged useful materials from the original chalet, ensuring a sustainable and resource-efficient build, they also encountered various non-biodegradable and non-recyclable materials such as UPVC windows, plastic corrugated sheeting, bitumen felt, asbestos roof coverings, plastic pipes, nylon carpets, fibreglass, and foam insulation. These materials, introduced during later modifications, had to be painstakingly transported back up the coast path and disposed of responsibly, reiterating the need for sustainable material choices in modern construction.


With the project taking over two years to complete, a significant investment was made in a scaffold tented over-roof to maintain a protected working environment throughout the construction period. This tent also allowed locally sawn ‘green timber’ including Douglas fir and oak to air dry on site for six months before being used, ensuring they were of optimal condition for quality building.


Formed in 2003 to specialise in sustainable and healthy buildings, all of ARCO2’s designs are made with sustainability at the forefront. Their name – derived from ‘architecture’ and ‘CO2’ – is a constant reminder that reducing carbon emissions through design is at the core of what they are trying to achieve. Each of their ten members of staff has hands-on building experience in creating some of the most sustainable properties in Cornwall. This forward-thinking approach has led to a well-earned win in the Carbon Reduction Impact Category at the CABE Built Environment Awards 2024 and ARCO2’s recognition as one of the leading architecture practices in the southwest.



The project at Edge O’ Cliff exemplifies ARCO2’s use of Passivhaus design principles, which set a new standard in energy efficiency and sustainable luxury living. Originating in Germany in 1996, Passivhaus design maintains a nearly constant temperature through superior construction, insulation and ventilation, requiring minimal additional heating or cooling. Edge O’ Cliff boasts U-values and air pressure test results which surpass Passivhaus requirements. 


Other features designed for energy efficiency include triple-glazed timber windows, cellulose fibre insulation, and a twin-wall timber frame using locally sourced wood. Innovative water and energy systems include sub-metered cold supplies, small bore hot water systems, and a whole-house MVHR with electric underfloor heating and a high-efficiency wood stove. Solar thermal tubes and a photovoltaic system have been installed to enhance energy generation. Meanwhile, landscaping by an ecologist, featuring indigenous plants and Cornish stone hedging, helps to seamlessly integrate the house into its natural coastal environment.


The owners commented: “Poor access, coastal location and ex-mining areas are normally enough to send most people running but none of this impeded our vision of creating the final outcome… This was no ordinary project but something very very special. The result is a house which exceeded our expectations in every sense.  Easy to use, low maintenance, very low running costs, and practically every small detail thought through. The overriding style was driven by function but somehow managed to produce a unique quality which is so rarely found in construction.”

“We started the project with a sense of responsibility to build a house that would do justice to the very special location which is held dear to ourselves and an enormous number of visitors as well as local residents. The result was met with absolute admiration not only for defying the obvious technical challenges but for a timeless build which sits peacefully next to the SSSI within an Area of Outstanding Natural Beauty.”



There is no doubt that the new Edge O’ Cliff offers an attractive blend of functionality and aesthetic beauty. It is a property which firmly lives up to modern standards of comfort and efficiency whilst also resonating deeply with its natural surroundings. The result is a timeless piece of architecture, which sits peacefully within its environmentally sensitive context. 


Described as “a tour de force in sleek, simple, design”, it is a building that is not only admired for its seamless integration to the landscape, but also for simply being there. Its sustainable, sensitive and innovative design is reflected in the many awards ARCO2 has won because of it. The best part is that Edge O’ Cliff and this precious corner of the world can be enjoyed for generations to come, without compromising the needs of the future, making it an exemplary example of sustainable design and high-quality architecture in Cornwall.



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