Kingspan’s Kooltherm range of products’ ability to deliver outstanding thermal performance, from minimal insulation thicknesses, has been used to full effect as part of the retrofit of an extraordinarily narrow house in central London. 

Slim House, a mid-terrace in Clapham, London, measures just 2.3 metres across internally.  The plot was originally used as access to stables from the high street and many of the rooms in the building were cramped and gloomy. Architects Alma-nac were hired to design an extension for the rear of the property.

Tristan Wigfall, partner at Alma-nac, said: “At Slim House our aim was to improve both the internal space and natural lighting against a tight budget. To achieve this we designed a rear extension with a slanted slate clad roof. This allowed several rooflights to be installed, greatly improving the natural lighting in the centre of the house.

The Kingspan Kooltherm products were a key part of this solution, allowing the building to achieve excellent thermal performance, without having to compromise on living space. Kingspan also provided excellent technical support regarding how best to insulate the unventilated roof build-up.”

To insulate the roof of the new extension, main contractors McGovern Carpentry installed two 75 mm layers of Kingspan Kooltherm K7 Pitched Roof Board between the joists. This was followed by a further 37.5mm thickness of Kingspan Kooltherm K18 Insulated Plasterboard, preventing thermal bridging through the joists and helping to achieve an overall roof U-value of just 0.14 W/m2.K. 

Kingspan Kooltherm K18 Insulated Plasterboard was also installed in various thicknesses as part of the extension wall build-ups. The product combines insulation, dry–lining and vapour control in one board, making it ideal for projects where space is at a premium. All products in the Kingspan Kooltherm range have a Class 0 fire rated insulation core and are manufactured with a blowing agent that has zero ODP and low GWP.

The new building layout is designed to make maximum use of space, with every nook and cranny utilised to keep the rooms uncluttered. The floor plates within the newly formed rooms have also been lowered, increasing the floor to ceiling height thereby creating a greater sense of space.

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