Cwrt Y Bedw
A new housing development designed with first-time buyers and families in mind
Case Study3 min read
With the help of a number of Kooltherm and Therma range products, a 1950’s house in Brockley, London has been reimagined as a contemporary construction, improving its energy efficiency and saving a significant amount of materials from ending up in landfill.
The site of the aptly named House-within-a-House was once home to a Victorian townhouse, which fell victim to bombing during the Second World War. The modest two-storey property that had been built to replace it, however, sat rather incongruously amongst its more stately neighbours. When the homeowners bought the property, it was with the vision of creating a new home suited to the needs of a modern family, that also respected the history of the area. Rather than calling in the wrecking crew, they worked with architects alma-nac to take a radically different approach.
LOCATIONLondon, UK
Architectalma-nac
The revised building design adds a third storey with a steeply pitched roof, providing additional living space for the family. A new outer-envelope was built around the existing structure with a layer of cavity wall insulation in between.
In order to reduce the additional footprint of the building’s ‘coat’, whilst achieving excellent thermal performance, Kooltherm products were specified for both the walls and roof of the building envelope. The boards offer leading thermal performance with thermal conductivities as low as 0.019 W/mK. This helps to keep the ‘building coat’ thin and lightweight, whilst also providing effective protection against the cold.
On the lower two levels, 50 mm of Kooltherm K108 was fixed within the cavity formed between the original masonry wall and the new pale brick exterior. In addition to the cavity wall insulation, a further 57.5 mm thickness of Kooltherm K118 was fixed on the inside of the masonry wall. Despite the slim thickness of the cavity wall insulation and insulated plasterboard, their excellent thermal efficiency allowed the construction to achieve a U-value of 0.15 W/m2K.
To maintain the clean interior aesthetic, heating on the ground floor is provided through an underfloor heating system. As part of this construction, a 100 mm thickness of Thermafloor TF70 was first fitted above the concrete floor slab. The underfloor heating pipes were then laid above the ground floor insulation followed by a 100 mm floor screed, improving the energy efficiency of the building from the ground up.
By adding a warm coat around the entire structure, the thermally inefficient 1950s dwelling has been turned into a highly insulated, airtight construction. The thermal performance of the property now vastly exceeds Building Regulations and gives a comparative reduction in CO2 emissions from 61.55 kg CO2/m2 to 16.49 kg CO2/m2.
"Kingspan products are well regarded and high performing and we often refer to Kingspan's technical guidance to review wall, floor and roof build-ups and ensure that we are achieving the target U-values. Although the project was not designed to meet any particular energy requirements, the clients’ brief was that they wanted to create an energy efficient and warm home. Specification of Kingspan products helped to achieve this and we greatly exceeded the energy requirements of building regulations. The clients have found that they typically don't have to turn on the heating on the upper floors and have low annual energy demands" - Tristan Wigfall, alma-nac
Images: Jack Hobhouse
Page updated 06/01/2026
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Products Used in this Project
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