Tregelly

Mawnan Smith, Cornwall

2026

Tucked into rolling hills that run between Mawnan Smith and Maenporth, Tregelly is a high-performing, low-carbon new-build residential house that we’re building to Passivhaus principles to LA Architects’ design.

Despite high specifications throughout the integrity of the building – designed to exceed standard building regulations – we have kept this project cost-effective for our client.

The build follows the core Passivhaus approach of a fabric-first design: a fully airtight envelope, continuous insulation, and triple glazing work together to minimise heat loss and all but eliminate draughts, keeping the home warm in winter and cool in summer with very little energy. More technical information is below.

Cladding exterior, Tregelly
Laying a parquet floor, Tregelly
Red cedar cladding, Tregelly
Cladding and roof detail, Tregelly

Tregelly, residential new-build Passivhaus principles, Mawnan Smith, 2026

Project details

Cost-effective built to Passivhaus principles (not certified).

Arts & Crafts aesthetic: 1920s arts and crafts influence with a client-realised modern twist.

MVHR system, full battery, solar array, and air-source heat pump.

Project development

Technical notes

A mechanical ventilation with heat recovery (MVHR) system supplies a constant flow of fresh, filtered air while reclaiming heat from the air it extracts, so comfort never comes at the expense of efficiency. Solar panels paired with battery storage further reduce reliance on the grid by capturing energy throughout the day and making it available when the house needs it most.

Where a standard Passivhaus build would rely on engineered I-joists, we took a conventional timber frame and pushed it somewhere new. By combining natural wood fibre insulation with standard rock wool and running an airtight membrane over standard OSB board, we engineered a wall build-up that delivers comparable thermal and airtightness performance using readily available materials — a smarter use of the client’s budget for the same end result. Berryman Construction were involved at every stage of this four-bedroom project, from the very first idea through design and development to the delivery of the completed home.