Natural Building Technologies’ (NBT’s) natural insulation systems
have been used in the construction of a modern and energy efficient
private home set within the unspoilt, traditional village of
Leafield. NBT’s ThermoPlan structural insulating blocks and Pavaclad
and Pavaroof woodfibre insulation systems deliver exceptional levels
of thermal insulation and satisfy the sustainability requirements
for the home. The systems’ breathability also ensures the long-term
integrity of the building’s structure and delivers a healthy living
The idyllic rural community is situated on the edge of the Cotswolds Area of Outstanding Natural Beauty (AONB). As such, architects faced the challenge of designing a residential property which satisfied the contemporary and sustainable specifications set by the client, but simultaneously incorporated the local vernacular form and materials, thereby complying with AONB planning restrictions. Playing a key part in the architects’ success were NBT’s high performing insulation systems.
Designed by A+G Architects, the building comprises two main masses and a lightweight timber and glass linking element. The front part of the home has a traditional finish, featuring Cotswold stone and a natural slate roof. In contrast, the rear element has a more contemporary appearance with a south-facing, curved structure, featuring a bespoke brise soleil, zinc monopitched roofing, and Cotswold stone and British chestnut cladding.
The walls of the property were predominantly constructed using NBT’s Thermoplan structural insulating blocks. ThermoPlan uses a true thin bed, 1mm thick mortar to secure rows of blocks, with interlocking dry vertical joints anchoring adjacent blocks along the row. The simplicity of the construction process enables ThermoPlan block walls to be typically constructed three to four times faster than conventional blockwork structures, with no limitation on the height that can be built in a day and no drying out shrinkage.
The honeycomb cross-section structure of the blocks delivers excellent levels of both thermal and acoustic insulation, while their microporous structure further benefits the insulation performance and delivers highly effective breathability. The blocks also provide crucial thermal mass, which helps to prevent overheating during the hotter summer months.
In addition, the building also has some timber frame wall sections, insulated using NBT’s Pavaclad woodfibre insulation system. This features NBT’s Pavatherm Plus woodfibre boards installed in a continuous layer over the frame, finished externally with the stone or timber cladding. Infill insulation is also used between the studs, and an OSB board is installed to provide racking strength.
Similarly, the Pavaroof system employed for the insulation of the building’s zinc monopitch roof features Pavatherm Plus woodfibre boards installed over the rafters with additional infill insulation between them.
Being manufactured from over 95% recycled timber, and drawn from FSC approved sources, NBT’s woodfibre insulation boards fulfill the sustainability criteria for the home, whilst simultaneously delivering ultra high levels of thermal performance. In addition, when installed within NBT’s high performing insulation systems, the woodfibre boards create a fully breathable construction, thereby maintaining a healthy environment, with reduced risk of mould formation and the associated health risks to occupants.
Use of NBT’s natural insulation systems resulted in U-values of 0.26 W/m2k for the ThermoPlan walls, 0.18 W/m2k for the timber frame wall sections, and 0.15 W/m2k for the roof.
Additional energy saving measures at the Leafield home include a mechanical ventilation heat recovery system, roof-mounted solar panels, and high performance double glazed windows.