In short: Thermal comfort simulation models how a space actually feels air and radiant temperature together, not just how much energy it uses. In a listed Victorian hall, it showed infrared panels were the simplest heritage-friendly retrofit, but heat pumps delivered far lower carbon and running cost over the building’s life. Only a holistic appraisal surfaces that trade-off (Rugani, Picco and Fantozzi, 2024).
Heritage buildings are where retrofit theory goes to be humbled. The envelope leaks heat by design and cannot be wrapped without erasing what makes the building worth keeping. The volumes are vast, the ceilings high, the occupancy intermittent: a few hours of community use, then days of emptiness. Every standard assumption behind modern heating design fails somewhere in that list and the UK has hundreds of thousands of such buildings, all facing the same demand: stay open, stay affordable, decarbonise.
A study by researchers including FREDS founder Marco Picco took one of them on properly: a historic Victorian hall in Brighton, mid-refurbishment, asking a deceptively simple question: “What is the right way to heat this building now?” (Rugani, Picco and Fantozzi, 2024). The answer required an unusually honest method, and produced an unusually useful verdict: the system that was easiest to install was not the best choice once comfort, cost and carbon were all allowed to vote.
Thermal comfort simulation that measures people as well as kilowatt-hours
What separates this study from a standard options appraisal is that it refused to let any single metric decide. The approach combined two strands:
Real occupants, really interrogated. As part of the hall’s renovation, two infrared ceiling panels (1 kW each) were installed in the community room as a live trial, not a thought experiment. Occupants’ thermal comfort was surveyed by questionnaire and analysed through the standard comfort framework (the PMV approach, which relates the thermal environment to how people actually report feeling, accounting for air and radiant temperatures, humidity, air movement, clothing and activity). Radiant systems make this essential: they warm people and surfaces directly rather than the air, so an air-temperature thermostat reading systematically misdescribes what occupants experience.
A calibrated dynamic model, stress-testing every alternative. In parallel, the hall was modelled in dynamic building energy simulation, with thermal comfort simulation across eight heating scenarios from a traditional gas boiler with radiators (H_1), through condensing boiler and gas heater options, air-to-air and air-to-water heat pumps, electric radiators, to the infrared ceiling panels themselves (H_7), plus a refined infrared scenario (H_8) controlled on operative temperature the average of air and radiant temperature that better represents what a person in the space feels. That control detail is the simulation honouring the physics of the system being simulated: judging a radiant panel by air temperature alone undersells exactly the mechanism it relies on.
Comfort, energy, running cost and environmental impact were then assessed together with UK energy prices applied at their real asymmetry (electricity around 0.27 £/kWh against 0.07 £/kWh for gas), which matters enormously to any electrification verdict.
What the numbers said
The simulation results redrew the intuitive ranking. In primary energy terms the total energy the building draws from the wider system the gas-fired scenarios were the heavy consumers, requiring on the order of 28,000 kWh more primary energy on average than the electric alternatives (gas scenarios totalling roughly 33,000–47,000 kWh). Electrification, in this leaky Victorian envelope, was directionally right.
But which electrification mattered just as much. The infrared panels delivered genuine virtues: simple installation with minimal intervention in the historic fabric (no pipework, no plant room, no wet system threading through a protected interior), targeted radiant warmth well suited to tall spaces and intermittent use, and positive occupant response in the live trial. For a heritage setting, those are not small advantages.
And yet the study’s headline conclusion cuts the other way: while infrared panels are easy to install, their environmental impact outweighs alternatives that demand more complex installation but repay it in economic returns and user satisfaction, the heat pump family chief among them. The reason is arithmetic rather than ideology. Direct electric resistance converts one unit of electricity into one unit of heat; a heat pump converts it into several. In a building this dissipative, running every winter for decades, that multiplier compounds into a decisive gap in both carbon and operating cost large enough to outweigh the panels’ installation advantages over the system’s life.
The study’s real finding, then, is not “infrared bad, heat pumps good.” It is that it depends on the nature of the building and on which lens you privilege easiest installation, lowest bills, best comfort, lowest carbon and that only a holistic assessment, weighing all four, surfaces the trade-off honestly enough for a building committee to make an informed choice. Pick the metric first and you have picked the system; the discipline is refusing to.
What this means beyond one hall in Brighton
For anyone responsible for a historic or community building, four transferable lessons:
- Electrify with a multiplier where you can. The primary-energy gap between gas and electric was large; the gap between resistance heating and heat pumps is the difference between electrification that merely complies and electrification that pays. Radiant systems are suitable when the space can be effectively kept at an average lower temperature with radiant panels providing the necessary top-up comfort; not the case for this Hall.
- Judge radiant systems on operative temperature. Specifying or simulating them on air temperature misrepresents both their comfort delivery and their consumption in opposite directions.
- Let occupants into the evidence base. The questionnaire strand caught what no meter can: whether people in the space actually feel comfortable. In community buildings, that is the service being purchased.
- Demand holistic appraisal before committing. The cheapest system to install, the cheapest to run, the most comfortable and the lowest-carbon may be four different systems. Knowing which trade you are making is the entire value of the analysis and in heritage buildings, where every intervention is constrained, it is the difference between a defensible decision and a lucky one.
The capability behind the case
This study is what FREDS consultancy work on heritage retrofit looks like in practice: calibrated dynamic simulation, multi-criteria appraisal, comfort fieldwork and heritage constraints, brought to a single defensible recommendation. The same research group’s platform makes the screening layer of that analysis comparing system and envelope scenarios dynamically a matter of minutes rather than weeks, which is what makes eight-scenario honesty affordable on ordinary projects, not just published ones.
Historic buildings forgive nothing and reward rigour. The Brighton hall’s lesson travels: easy and right are different questions and only the full analysis tells you when they disagree.
Facing a heritage heating decision? FREDS consultancy team applies this exact methodology to live projects talk to us about your building.
Related reading
Frequently Asked Questions
What is thermal comfort simulation?
What is the best way to heat a heritage building?
Why are heat pumps better than infrared panels for heritage retrofit?
Should radiant heating be assessed on air or operative temperature?
References
Written by Marco Picco, PhD co-founder of FREDS4Buildings and a building-physics lecturer at the University of Lancashire, whose work on building energy simulation has been published in Energy & Buildings , Building and Environment and the IBPSA Building Simulation conference proceedings. About Marco Picco
Reference: Rugani, R., Picco, M. and Fantozzi, F. (2024). Thermal comfort and environmental impact in the heating system refurbishment of a Victorian hall with infrared ceiling panels. Building Simulation Applications proceedings. View paper
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