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Treading lightly

In a world where every effort counts towards lowering our carbon impact, ARCO2 helps us to reconnect with the earth through the very walls of our home.

In 1996, the Passivhaus Institute in Germany developed a set of building principles that would prove to be the gold standard in energy efficiency, translated to mean, quite literally, passive house. Created to rigorous energy efficient design standards so that they maintain an almost constant temperature, Passivhaus buildings are so well constructed, insulated and ventilated that they retain heat from the sun and the activities of their occupants, requiring very little additional heating or cooling at all.

It is these evolving standards that the team at ARCO2 weave into their own principles as they work to tread lightly on the earth and bring sustainability into each house they create, having recently earned a win in the Carbon Reduction Impact Category at the CABE Built Environment Awards 2024. Each project is designed and constructed with the surrounding environment in mind, using natural and local materials coupled with the latest renewable technologies.

One such Passivhaus-inspired project completed in 2023 is Keynvor. Overlooking the ebb and flow of the tide that washes the shore of Mawgan Porth, this dual but interconnected structure exemplifies this sustainable approach. “As with many of our builds that are close to the sea,” explains Director of ARCO2, Ian Armstrong, “a high level of insulation is necessary, so priority was given to wall thickness with recycled newspaper blown into the wall structure to a width of nearly 400mm.”

A high level of thermal insulation was specified, one that removes direct heat transfer between the outside and the controlled internal environment, resulting in a lower heat load to the internal spaces. By reducing the amount of temperature change the level of interstitial condensation risk was lowered. This has measurable positive benefits for the longevity of the property, as material degradation is lessened due to moisture generation and retention being reduced to a minimum. Defined by Gro Harlem Bundtland as a “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”, it seems sustainability has been woven into the walls of Keynvor, future proofing it for generations to come.

Surrounded by the wild and wonderful Cornish weather, the exterior had to be carefully considered. The detailing, implemented by Nathan Davis, has been meticulously considered to make the floor-to-ceiling windows wind and water tight. This is imperative to the coastal location where winds can reach 90mph. “The materials that are selected for our sustainable architecture designs to become tangible have a hierarchy of credentials that dictate our choices,” Ian continues. “We would always seek out those that are sourced locally first. The stone and cut timbers in the case of Keynvor were acquired locally with more specialist materials imported from as near to the site as possible.”

Keynvor has an air-source heat pump to provide the primary space and water heating requirements. The main use of the property will be during the summer months when a heat pump solution is most efficient. What is particularly innovative is the capital investment into a single heating system for both properties. A carefully planned super-insulated heat loop pipework system had to be installed deep into the ground to reduce the heat losses to a minimum. Mechanical heat recovery and ventilation (MVHR) solutions are essential in maintaining a healthy living environment. They are a ‘must have’ to each and every ARCO2 sustainable architecture design. The location of the MVHR with a short pipework run to the outside is essential to gaining the best efficiencies in heat recovery.

A truly impressive achievement shared by James Huxley and Nathan Davis, the end result was the culmination of a synthesis of energy and ideas by both partners. As Nathan acknowledges: “It’s the most enjoyable outcome to see the success of a well thought through design being physically realised.” Light and airy, timber panelling and micro-cement floor tiling makes its way across the open-plan layout of the first floor, the main living space enjoying the awe-inspiring view of the ocean beyond. In a reverse layout, the bedrooms are located in the level below, and the interior design of the home, created by Nicola O’Mara, serves to mirror the beauty of the location and the unique architecture of Keynvor, weaving through interconnected spaces.

“Virtual reality (VR) simulations allowed us to work out the positions for the windows to maximise the sea view and orchestrate the cast of natural light within the building,” James explains. “It also facilitated seamless and efficient on-site construction with off-site 3D modelling prior to the start of the build.” A green roof, achieved by the planting of sedum, was implemented to minimise the impact of the foreground building on the site line and to integrate with the view of the headland beyond.

Understandably, the clients were delighted with the end result, overwhelmed by the quality and comfort provided by Keynvor. Financially future proof, and with low energy demands designed upon Passivhaus principles, this ARCO2 home can cater for this family’s needs as well as future generations, coupled with the ability to support multigenerational living, all wrapped up in a sustainable, well-considered design bundle.”


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