Sustainable

House

Conversion

The Brief

Our clients sought to relocate from London to establish a sustainable family home in a rural Somerset setting. They required a property that balanced environmental responsibility with contemporary living standards, whilst remaining financially viable to build and economical to run.

Having previously worked with the landowner and secured the original planning consent for the site, we were well-positioned to identify this opportunity and guide the clients through acquisition and feasibility. This established relationship ensured the design development could proceed efficiently, with clear understanding of both the site’s potential and its planning constraints from the outset.

Site Context & Challenges

The project occupied a redundant agricultural building in open countryside, where Local Planning Policy typically restricts new residential development. The route to consent lay in utilising Class Q Permitted Development Rights, which permit conversion of certain agricultural buildings to residential use without full planning permission.

However, Class Q legislation imposes strict limitations: the works must constitute genuine conversion rather than rebuild. This meant retaining the existing structural steel frame, maintaining the original footprint and maximum height, and preserving the building’s agricultural character and massing. Glazing needed to be positioned discreetly to avoid domesticating the external appearance.

The existing steel structure required strengthening with timber elements, executed in a manner that reinforced the conversion status rather than suggesting new construction. Every design decision needed to balance residential comfort with regulatory compliance and the preservation of the building’s rural, utilitarian character.

Our Approach

The overarching ambition was to deliver a certified Passivhaus – achieving exceptional thermal performance and minimal operational energy consumption through high-specification insulation, airtight construction, and mechanical ventilation with heat recovery (MVHR). This approach ensures year-round comfort with remarkably low heating demand, dramatically reducing both running costs and environmental impact.

Critically, the project demonstrates low embodied carbon through the retention and adaptive reuse of the existing agricultural structure. Rather than demolition and replacement, the design gives new purpose to a redundant building, significantly reducing carbon impact whilst respecting the site’s rural context.

Materials & Aesthetic

Externally, the building employs timber wall cladding and metal roofing that reference traditional agricultural construction. These robust materials will weather naturally, allowing the structure to sit comfortably within the landscape whilst maintaining the solid, barn-like character required by planning policy.

The interior adopts a deliberately minimalist, industrial aesthetic. Polished concrete floors provide durable, contemporary surfaces with excellent thermal mass properties. Structural elements and MVHR ductwork remain exposed, expressing the building’s construction logic and environmental systems honestly. This approach delivers refined spaces with subtle industrial character – robust yet carefully detailed, functional yet sophisticated.

Technical Innovation

The project successfully navigates the tension between Class Q requirements and Passivhaus certification – two frameworks that rarely intersect. Achieving airtightness standards whilst working within the constraints of an existing agricultural frame required careful detailing and a collaborative approach with specialist contractors.

The retention and strengthening of the existing structure, combined with the Passivhaus envelope, demonstrates that high-performance environmental design need not rely on new construction. The project proves that redundant rural buildings can be transformed into exemplary low-energy homes whilst preserving their original character and minimising carbon impact.

Challenges & Solutions

The principal challenge lay in reconciling competing requirements: Class Q legislation demanded preservation of the agricultural building’s character and structural identity, whilst Passivhaus certification required exceptional envelope performance and airtight construction. These objectives don’t naturally align when working with an existing steel-framed agricultural structure.

Additionally, the glazing strategy needed careful consideration. Whilst generous daylight and views were essential for residential quality, too much visible glazing would compromise the building’s agricultural appearance and potentially jeopardise Class Q compliance.

We strengthened the existing steel frame with timber elements in a manner that read as structural enhancement rather than new construction, maintaining the conversion narrative required by Class Q whilst providing the robust framework needed for the high-performance envelope.

Glazing was strategically positioned to remain largely hidden from external viewpoints, concentrated on elevations screened by landscape or oriented away from public vantage points. This preserved the solid, barn-like external character whilst flooding interior spaces with natural light.

The technical detailing focused on achieving airtightness within the constraints of the adapted structure, working closely with the construction team to resolve junctions and interfaces that would satisfy both Passivhaus testing requirements and the Class Q framework.

The Result

A certified Passivhaus of 4,760 sq ft that successfully navigates the complex intersection of planning policy, environmental performance, and architectural quality. The project delivers exceptional thermal performance with minimal operational energy costs, comfortable light-filled contemporary living spaces across a single expansive storey, and successful adaptive reuse that significantly reduces embodied carbon.

The refined industrial aesthetic celebrates honest materials and construction, whilst full compliance with Class Q requirements achieved Passivhaus certification – a rare combination that demonstrates intelligent design can work within regulatory constraints rather than against them.

Key Features

• Certified Passivhaus with near-zero heating demand
• 4,760 sq ft single-storey living space
• Exposed structural elements and visible MVHR systems
• Polished concrete floors with excellent thermal mass
• Natural timber and metal cladding
• Strategic glazing providing abundant light whilst preserving external character
• Set within almost four acres of Somerset countryside
• Featured in The New York Times and The Modern House