Built to teach: Scotland’s living retrofit demonstrator

The deep retrofit of Scotland’s National Retrofit Centre (SNRC) has transformed an industrial unit built in 2000 into a live, working demonstrator of best practice in non-domestic retrofit.

Led by BE-ST and supported by the Scottish Government’s Public Sector Heat Decarbonisation Fund, the project showcases how innovative design and construction can dramatically reduce energy demand and decarbonise heat at scale. Phase 1 of the project includes a fabric-first approach using natural, locally sourced materials and modern methods of construction. With an innovative cascaded heat pump and solar PVT system, the building now generates more energy than it consumes, setting a new benchmark for non-domestic retrofit in Scotland’s net zero journey.

Key stats

Construction: Off-site CLT and JJI joists panelised system with hemp insulation
TFA: 810.33 m²
Build start date: 2024
Completed: 2025
Certified: Phase 1 of 2 in a step-by-step retrofit project aiming for EnerPHit certification.

Image credit: Built Environment - Smarter Transformation

The retrofit of the SNRC goes beyond energy efficiency to create a living testbed for Scotland’s decarbonisation ambitions. Designed with PHT members John Gilbert Architects (JGA) and Luths Services, the centre will ultimately meet both the EnerPHit and Scottish Net Zero Public Sector Building standards. The project demonstrates how large-scale, multi-use buildings can achieve ultra-low operational energy targets. BE-ST is documenting decisions, processes, and learnings in real time, ensuring that others in the public and private sectors can benefit from the experience. The centre is not just a building, but a resource for replicating successful retrofit strategies across Scotland and beyond.

The intention here isn't that someone would pick this up and replicate it exactly as it has been delivered, but this is like a menu of different approaches and systems that could be deployed. The project learnings are not only relevant to non-domestic retrofit, but within any retrofit context as the challenges of finance, timescales, disruption, existing data and supply chain access are universal.

Gavin Johnston, Project Manager, BE-ST

Construction

The project embraces a fabric-first strategy, balancing energy efficiency with embodied carbon impacts. It uses homegrown Scottish CLT panels insulated with locally sourced natural fibre materials, assembled offsite for speed, quality, and minimal disruption. The insulated CLT façade system, manufactured on the Innovation Campus, together with a modular offsite insulated roof system delivers outstanding thermal performance while acting as a carbon sink.

Embodied carbon

Every material decision has been guided by low embodied carbon aspirations, local supply chain support, and innovation. Sustainably sourced timber, ultra-low carbon bricks, and circular design principles have created an envelope that captures more carbon than it emits over its lifecycle. By leveraging offsite manufacturing, the team achieved an ambitious programme while showcasing how Scotland’s natural resources and systems can power low-carbon retrofit at scale.

U-values

Roof: 0.12 W/m²K

Loft insulation: JJI Joists panels + nyrock rockwool insulation

Wall: 0.139 W/m²K

External walls: CLT + JJI Joists + hemp insulation+ timber cladding panles

Windows: Timber frame/ aluclad triple glazed windows and doors + reduced window area

Floor: as existing for Phase 1 & 0.126 W/m²K for Phase 2

Solid floor insulation

Building performance

Designed energy performance

Airtightness n₅₀ (≤ 1.0 ACH @ 50 Pa)

Existing: 22 ACH,

Phase 1: 3ACH, Phase 2: 1 ACH

Space Heating Demand (≤ 25 kWh/m².a)

Existing: 347 kWh/m².yr,

Phase 1: 95 kWh/m².yr, Phase 2: 24 kWh/m².yr

Primary Energy Demand: (≤ 120 kWh/m².yr)

175 kWh/m².a

*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria.

Services

To replace the building’s former gas-based heating, the SNRC now features the UK’s first integrated zero direct emissions heating system of its kind. Developed with NIBE Energy Systems Limited and PREAH, the hybrid system combines ground and air source heat pumps with 42 photovoltaic-thermal (PV-T) panels, smart controls, and a cascaded configuration to ensure maximum efficiency even at peak demand.

Mechanical ventilation with heat recovery (MVHR) complements the high-performance fabric, supplying a continuous flow of fresh, pre-heated air while minimising heat loss. Together with energy-efficient lighting and controls, these systems deliver a low-carbon, high-comfort environment while providing live performance monitoring and real-time energy data, turning the centre into both a demonstrator and a data-rich research hub.

Image credit: Built Environment - Smarter Transformation

Challenges & lessons learned

Funding & timescales: Securing Scottish Government funding through the Salix-delivered Public Sector Heat Decarbonisation Fund was vital but came with tight delivery deadlines. A phased approach and offsite manufacturing allowed the team to meet the 12-month funding window without compromising quality or ambition.
Balancing ambition & budget: Inflation and unforeseen costs required careful reprioritisation. Some measures, such as the PV array, were deferred to future phases to protect the project’s core carbon reduction objectives.
Maximising public investment: BE-ST used the funding to deliver impact beyond direct carbon savings by ensuring learnings and best practice would be shared widely with the sector.
Phased retrofit: The project shows how large-scale estates can decarbonise incrementally, providing a practical template for other public bodies.
Contingency & flexibility: Financial forecasting, strategic phasing, and open dialogue with funders were essential to maintaining momentum and outcomes in a fast-changing market.

As anyone who has ever undertaken a comprehensive retrofit or refurbishment programme knows, challenge and compromise are a near constant throughout the delivery. The way we responded to these through adaptation and innovation with considered phasing and maximising off site construction has determined the ultimate success of the project.

Gavin Johnston, Project Manager BE-ST

Key team

Client: BE-ST
Architect: John Gilbert Architects
Passivhaus Designer/ Consultant: John Gilbert Architects
Contractor: Clark Contracts
Structural engineer: Narro Associates
M&E consultant: Luths Services
Client: WARM (Phase 1)

Find out more about the project at the UK & Ireland Passivhaus Conference 2025 on 8 October 2025, where Caitriona Jordan, BE-ST, Barbara Lantschner, John Gilbert Architects, Dan Gates, Luths Services and Gerry Cummins, Clark Contracts will be speaking in the 'How to deliver Passivhaus Retrofit: Practical Experience Case Studies' section of the Conference.

UK + IRL Passivhaus Conference 2025, 7-8 October, Belfast & online