This summer, a simple question will be posed to the public in the centre of Dublin: which block of ice do you think will last longer?
The answer will be visible in plain sight, in real time, over several weeks. And for anyone who works in the built environment (or lives in a building, which is everyone) it is worth paying attention to.
The Ice Box Challenge is coming to Ireland for the first time, set within the grounds of Trinity College Dublin, with a live reveal at ZEB Summit on 23 September at the RDS. Mosart’s architectural team is designing and building both structures.
What the Ice Box Challenge is
The premise is deliberately straightforward. Two structures are placed side by side in a public location. From a distance, they appear identical. Each contains a large block of ice. Neither has any mechanical heating or cooling. They simply sit outside, exposed to the same weather, the same sun, the same ambient temperature.
The difference is in how they are built.
One structure is constructed to conventional building standards, representative of typical construction practice in Ireland today. The other is built to the Passive House Standard, with full insulation, no thermal bridges, airtight construction, and high-performance glazing.
As the weeks pass, the gap between the two becomes visible to anyone walking past. In previous events across Europe, the US, and Canada, the results have been striking: in comparable warm conditions, the standard box has typically retained as little as 7% of its original ice, while the Passive House box has held approximately 42%. The experiment requires nothing more than time and weather.
Why this matters now
The Ice Box Challenge is not a new concept. It has been staged in Brussels, Vancouver, Glasgow (during COP26), Seattle, Washington DC, Philadelphia, and across the US. Each time, the public response has been the same: people find it unexpectedly arresting. Abstract arguments about U-values and thermal bridging become concrete when you can watch them play out over time through a window.
What makes the Dublin installation different is the addition of live sensor data. Sensors placed inside both structures will track internal conditions continuously, with temperature and humidity readings from both boxes available online in real time. The public can follow the performance gap as it develops, not just see the result at the end.
For a country moving towards mandatory zero-emission building standards, this kind of visible, comparative demonstration arrives at exactly the right moment. Buildings account for a substantial share of Ireland’s energy consumption and carbon output. The transition to high-performance construction is no longer optional, but for many in the industry the performance benefits of Passive House remain abstract or, worse, disputed. The Ice Box Challenge removes the abstraction.
A collaboration with Trinity College Dublin and PHAI
The Dublin installation is being delivered in partnership with the Passive House Association of Ireland and Trinity College Dublin. The academic partnership brings research rigour to the project alongside public reach, connecting the demonstration to ongoing work in climate adaptation engineering at Trinity.
For Mosart, which has been involved in bringing the challenge to Ireland, the value lies in the installation’s ability to communicate what high-performance buildings actually do. The science of energy-efficient design can shape a more sustainable future, but only if people understand what it means and can see it demonstrated in terms they do not need a technical background to interpret.
Mosart’s Managing Director, Tomás O’Leary, has spoken about the significance of bringing the Ice Box Challenge to Ireland for the first time, noting that it offers a powerful way to show how building performance affects energy use and inviting the public to engage directly with the science behind what is, at its most fundamental level, the problem of global warming.
What Mosart is building
Mosart’s architectural team is designing and constructing both structures using Modern Timber Construction. The brief demands that the two boxes look identical from the outside while performing entirely differently from within, a constraint that makes the design task more interesting than it might first appear and one that mirrors the challenge facing the construction industry more broadly.
The Passive House box will be built to the full standard: continuous insulation, carefully detailed junctions to eliminate thermal bridging, an airtight envelope, and Passive House-specified glazing. The conventional box will reflect current standard practice, built to regulatory minimum rather than performance maximum.
Both structures will be instrumented and open to the public. The boxes will be on display at Trinity College Dublin throughout July, with the results observable by anyone passing through the grounds. The live reveal takes place at ZEB Summit on 23 September at the RDS.
ZEB Summit 2026: where the reveal happens
ZEB Summit 2026 takes place at the RDS, Dublin on 23 September. The Ice Box Challenge reveal is part of a wider programme that will bring together architects, engineers, developers, local authorities, and sustainability professionals from Ireland, the UK, and internationally.
The Summit will place a strong focus on both existing buildings and the delivery of high-performance new builds, covering retrofit, zero-emission standards, embodied carbon, and the technical and commercial decisions that drive performance in practice.
If you work in the built environment and want to understand where Irish and UK construction is heading, this is the event to attend.
Secure your place at ZEB Summit 2026 →
The Ice Box Challenge in Dublin is delivered in partnership with the Passive House Association of Ireland and Trinity College Dublin. Mosart Group is hosting ZEB Summit 2026.