The art of a high-performing home

A stunning Devon home with sea views also offers high-performance and thermal efficiency thanks to rock mineral wool insulation. Specify & Build reports.  

Labrador House is a property born out of the surrounding landscape. When a couple were looking for a new home near the village of Shaldon, Devon, they found the perfect spot, nestled in the coastal cliffs. They decided they wanted to build a home that followed the contours of the cliffside and used a dark palette of materials to blend into the background of the surrounding woodland. 

As well as being architecturally stunning, Labrador House is a high-performing home with wall U-values of 0.15 W/m2K, achieved using Knauf Insulation’s Rocksilk RS45. 

Connecting to the landscape 

VESP Architects specialise in unique residential projects in the south-west of England. The challenge was to build a 550m2 home that didn’t impose on the landscape as a single mass. Instead, the property would be broken up into three main areas, linked by flat roof corridors covered with coastal plants. 

As well as this decentred design, VESP wanted to achieve a high standard of thermal efficiency, taking advantage of the large glazing areas on the seaward side of the property. The property uses two air source heat pumps and mechanical ventilation with heat recovery (MVHR) to extract air from the bathroom and kitchens and cycle warm air throughout the house. These technologies perform most efficiently in a well-insulated environment. 

An airtight thermal envelope 

To achieve an airtight and efficient thermal envelope, the timber clad sections of the house used 175mm slabs of Rocksilk RS45, a rock mineral wool product, fitted between the studs of the steel frame system.  

Rocksilk RS45 is a versatile rock mineral wool slab that can be used in multiple applications including floors, pitched roofs and internal walls, as well as light steel frame and timber frame walls. It is non-combustible, with the best possible Euroclass A1 reaction to fire classification, and is manufactured using ECOSE Technology, a plant-based binder that contains no added formaldehyde or phenol. 

Installation is key 

One of the biggest factors in the specification of Rocksilk RS45 was the installation process. Director Ian Phillips explains: “We now specify mineral wool for any full-fill insulation we need. Rigid boards such as PIR perform well on paper but are not quality control friendly – the boards don’t sit as closely to the timber as they need to.  

“Mineral wool can be pushed into a space and fills it so easily. Over the past decade we’ve used mineral wool more and more – it’s a key part of our specification process now.” 

Mineral wool products like Rocksilk RS45 are flexible enough to adapt to minor imperfections in the substrate, in this instance timber cladding. At abutting edges, the fibres will also ‘knit’ together to create an airtight layer of insulation without taping. 

Ian also explains that Knauf Insulation’s technical support makes them his first choice as a supplier of mineral wool. “Knauf Insulation have always been very approachable whenever we’ve needed technical advice,” he says. “The resources they have are useful – the technical and installation documents and the U-value calculator. It’s good to know I can rely on them for support when it’s needed.” 

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