TV presenter Guy Martin put Passivhaus principles to the test in an 'Ice Box' experiment for his Channel 4 House Without Bills programme, with the results now available to watch on YouTube.

As part of a series of building physics trials for the programme, Martin ran an Ice Box Challenge to explore how high-performance homes perform during hot weather.

Two near-identical sheds were used: one built to Passivhaus standards and the other to current building regulations. Each was filled with 0.5 tons of ice and left for a week at Martin's Lincolnshire home in August 2025. When opened, the Passivhaus shed had lost 30% of its ice and measured 5 degrees C inside, while the building regulations shed had lost 60% of its ice with an internal temperature of 11 degrees C.

The well-travelled ice boxes originated in Glasgow and are currently used at NMITE in Hereford to support ongoing training. They were briefly relocated for Martin's experiment before returning to NMITE.

Martin said: "This was an experiment to see - are we all going to melt in well-insulated houses? Insulation works in both directions, it takes longer for the heat energy from the sun outside to penetrate all of this insulation to get to the ice. So, will a well-insulated house cook you in the summer? No it won't, it'll keep you cooler.

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Jon Bootland, Chief Executive, Passivhaus Trust, added: "The experiment demonstrated that the Passivhaus shed is good at keeping warmth in a building in the winter months and keeping things cool in the summer months, in much the way a thermos flask works. The ice boxes are a great visual way to help dispel the myth that Passivhaus buildings lead to overheating. The extra insulation and airtightness actually helped reduce the ice melting in the Passivhaus shed. the first all-electric phase of Agar Grove and we have been able to deliver these Passivhaus buildings using products and technologies that are common to buildings of this typology in the UK – demonstrating that low-energy Passivhaus projects aren't at odds with mainstream construction."

Ben Shirley, Assistant Professor, NMITE, said: "The ice boxes, filmed as part of Guy Martin's House Without Bills programme, highlight the role of practical demonstration in communicating the benefits of high-performance construction to a wider audience. They show how NMITE and the Centre for Advanced Timber Technology work with partners to bring building performance to life. Together, we're making high-performance construction more visible, understandable and achievable."

The experiment was delivered through collaboration between the Passivhaus Trust, The New Model Institute for Technology and Engineering (NMITE) and Edinburgh Napier University, with support from the UK Research and Innovation funded Centre for Net Zero High Density Buildings, Scotland Beyond Net Zero, and the Housing, Construction and Infrastructure Skills Gateway as part of the Edinburgh and South East Scotland City Region Deal. The Ice-Boxes were originally constructed by Built Environment – Smarter Transformation, with preparation support from Herefordshire-based Mike Whitfield Construction.

Collaboration remains central to driving impact across the sector. Alongside the demonstration, two new strategic partnerships were announced, including one between Architecture and Design Scotland and BE-ST, Scotland's national innovation centre for construction and the built environment, to better align design and innovation in the built environment.

At NMITE, the ice boxes form part of applied teaching and industry engagement, helping students and practitioners connect design intent with real-world performance on building quality and low-carbon design.