Thermal Comfort, Overheating, and the Human Factor
In the built environment, we have become incredibly proficient at designing for the heating season. We know how to insulate, we know how to seal, and we know how to decarbonise our heat sources. But as our climate shifts and our building standards evolve, a new challenge is emerging in cooler climates: cooling!
In this episode of Air Quality Matters, I sat down with Paul D O'Sullivan from Munster Technological University to navigate the complex intersection of ventilation, thermal comfort, and the rising risk of overheating in our building stock.
Beyond the Thermostat: Defining Comfort
We often treat indoor environmental quality (IEQ) as a checklist of contaminants to avoid. However, thermal comfort is distinct—it is not just about the absence of a negative; it is about the presence of an environment that allows us to thrive.
Paul articulates a fascinating shift in how we view our buildings: moving from simple "shelter" to spaces that are "fit for purpose." A significant portion of our conversation explores the psychology of comfort. We discuss the tension between the "luxury" of perfectly controlled environments and the human need for agency.
One of the most compelling insights Paul shares is the concept of adaptive comfort. We discuss why a room full of building professionals can sit in an uncomfortable meeting room, feeling helpless because they cannot open a window, and how the ability to intervene—to put on a jumper or open a blind—changes our physiological and psychological tolerance for temperature.
The Cooling Ladder Design Ethos
A key takeaway for architects and engineers listening to this episode is Paul’s framework for designing resilient buildings, which he calls the "Cooling Ladder."
Without giving away the full depth of the technical specification discussed, the conversation outlines a cascading hierarchy of design interventions:
Preventative Measures: Stopping heat ingress before it happens.
Modulating Measures: Using thermal mass and building physics to manage the load.
Dissipative Measures: The role of ventilative cooling.
Mechanical Intervention: The final rung, only to be used when passive measures are exhausted.
Paul argues that we often jump straight to mechanical cooling without fully exploiting the building’s passive potential, specifically the "battery" effect of thermal mass and night cooling strategies.
The Performance Gap and Data Blind Spots
We also delve into the uncomfortable reality of the "performance gap." Theoretically, we know how our buildings should perform. In reality, the data tells a different story.
Paul shares striking findings from recent research, including a revelation that compliance tools (like DEAP/SAP) may be under-predicting energy use by up to 40% compared to real-world monitoring. This segment of the podcast is crucial for anyone relying solely on design-stage modeling. It highlights the urgent need for post-occupancy evaluation (POE) and the importance of treating buildings as living systems that require "tuning" rather than static assets.
Unexpected Resilience: Schools as Climate Shelters
One of the most intriguing parts of our discussion centers on resilience. As heatwaves become more frequent, how do we protect the vulnerable? Paul introduces the concept of using schools as "climate shelters."
Since schools are often unoccupied during the hottest summer months and are centrally located in communities, they possess the potential—through minor retrofits and night cooling strategies—to become safe havens for vulnerable demographics during extreme heat events. It is a thought-provoking look at how we might reimagine the utility of existing public infrastructure.
Why You Should Listen
This conversation moves beyond the dry physics of overheating. It touches on the socio-economic impacts of poor design, the friction between air quality (pollution) and natural ventilation, and the future of "hybrid" cooling systems.
Paul O’Sullivan brings a refreshing mix of academic rigor and practical reality to the table. If you want to understand why your "A-rated" energy-efficient design might be creating an overheating liability, or why the future of cooling isn't just about air conditioning, this episode provides the context you need.
One Take: Is Your Good Home Office Actually Productive?
Paper: Home as an Office: Investigating the associations between indoor environmental quality, wellbeing and performance.
In this week’s One Take, we dissect a paper that challenges the engineer’s reliance on sensors. The researchers monitored 95 work-from-home setups, measuring objective data (PM2.5, CO2, acoustics) alongside the occupants' subjective perceptions of their space.
The findings were surprising. The study revealed that objective sensor data had a weaker association with productivity and wellbeing than the occupants' subjective feelings.
Essentially, if a person felt they had a good view, ergonomic furniture, and agency over their environment (like opening a window), their performance improved—even if the sensors picked up slightly elevated CO2 or pollutants. Conversely, specific annoyances, such as persistent kitchen odors or noise interruptions, had a statistically significant negative impact on mental vitality.
This doesn't mean air quality doesn't matter. Rather, it validates the idea that human perception is a powerful driver of performance. It suggests that a holistic approach to design—considering aesthetics, control, and comfort—is just as critical as hitting a specific PPM target.
The Air Quality Matters Podcast in Partnership with
Zehnder Group - Farmwood - Eurovent- Aico - Aereco - Ultra Protect -
The One Take Podcast in Partnership with
SafeTraces and Inbiot
Do check them out in the links and on the Air Quality Matters Website.
If you haven't checked out the YouTube channel its here. Do subscribe if you can, lots more content is coming soon.