Is Moisture the Forgotten Pollutant of the Built Environment?
Moisture is a constant topic in the built environment, yet we rarely stop to unpack the foundational building blocks of how it actually behaves. We toss around terms like relative humidity, vapour pressure, and psychrometrics, but how often do we truly grasp their real-world implications?
In the latest episode of the Air Quality Matters podcast, we are joined by David Schurk , owner of HVAC Insight Consultants. With over 40 years of experience in the HVAC industry, specialising in complex, mission-critical environments like healthcare and aerospace, David is nothing short of a dehumidification Jedi.
This conversation strips away the complex graphs and challenges us to define building physics in plain English. If you want to understand what is really happening to the air in your spaces, this episode is an absolute must-listen. Here is a glimpse into what we covered.
The Pollutant Debate and the Surgeon’s Dilemma
We often lump moisture in with indoor air quality (IAQ) and indoor environmental quality (IEQ), but is it technically a pollutant? David makes a compelling case that it is. While it may not possess the toxicological properties of VOCs or particulate matter, moisture profoundly impacts both human physiology and building integrity.
David paints a vivid description of the environment inside a hospital operating room. Surgeons, heavily gowned and working under intense lights, rely on the evaporation of perspiration to maintain their core body temperature. When a space is incorrectly conditioned—resulting in high humidity despite low temperatures—surgeons can face severe heat stress, feeling as though they are "wrapped in cellophane doing jumping jacks." Hearing David describe the cascading failures of poorly managed OR humidity perfectly illustrates why getting this right is a matter of critical performance, not just basic comfort.
The Fish Tank Illusion: Why Relative Humidity Can Deceive You
One of the most interesting segments of the discussion for me tackles the limits of Relative Humidity (RH). David uses a brilliant "fish tank" analogy to explain why relying solely on RH can be a massive blind spot for building professionals.
Because air expands and contracts with temperature, a room at 75°F and 50% RH holds a vastly different absolute amount of water than a colder room at the same percentage. Opening a window on a seemingly dry but warm day might actually invite a massive moisture load into a cooler building simply because the vapour pressure outside is higher.
To truly manage a space, David argues that we need to look beyond RH and embrace dew point temperature and absolute humidity. The psychrometric chart might look like the structural lattice of a roller coaster to the uninitiated, but as David explains it, understanding the relationship between sensible heat and moisture is vital for predicting how air will behave.
Cold Spots, Mould Spots, and the Physics of Surfaces
Air is only half the battle; the surfaces within a building introduce a whole new dynamic. We discussed the distinct differences between moisture condensing on non-porous surfaces (like chilled HVAC registers) and the hidden dangers of porous, adsorptive materials like drywall.
David explains the fascinating and destructive process of capillary condensation, where hygroscopic materials literally pull water molecules out of the air, even if the space hasn't reached the dew point.
Adding the D to HVAC
Air conditioning is primarily about sensible cooling, and in traditional systems, moisture removal is merely a byproduct of making the air cold. But as we push for higher energy-efficiency standards, warmer coil temperatures in modern AC units are failing to adequately dehumidify spaces.
David introduces the concept of HVAC-D—advocating for dehumidification to be treated as an independent and equally important pillar of climate control. He also breaks down the fascinating mechanics of desiccant dehumidification.
Unlike traditional coils that turn into blocks of ice when pushed to extreme dew points, desiccants capture moisture at the molecular level. Hearing David detail how these systems manipulate vapour pressure to achieve hyper-dry environments (like those required for semiconductor or lithium battery manufacturing) is an absolute masterclass in mechanical engineering.
One Take: The Psychology of Clean Air Tech Adoption
While we love to geek out on the physics of air, none of our engineering matters if the public refuses to adopt the solutions. In this week's One Take, we explore a fascinating recent study published in the Indoor Air journal titled: "Indoor air quality: predicting and comparing protective behaviours in Germany and Portugal."
Using the Protection Motivation Theory, researchers surveyed 800 people to understand what actually drives a consumer to invest in IAQ tech, like sensors or purifiers. The findings prove that a one-size-fits-all marketing approach is doomed to fail:
Germany: Adoption is heavily driven by self-efficacy (the feeling of "I am capable of installing and managing this") and a profound sense of duty to protect close family members.
Portugal: Consumers are highly pragmatic. They don't care about autonomy; they care about response efficacy. They are sceptical and will only adopt the tech if you can absolutely prove that it works to improve their health.
Perhaps the most surprising takeaway? Fear doesn't sell. In both countries, perceived personal vulnerability to illness had almost zero impact on adoption. Instead, people are motivated by acknowledging the global severity of air pollution, combined with an empowering, proven solution. If you are a manufacturer, policymaker, or installer, this episode will completely reshape how you communicate the value of your services.
Indoor Air Quality: Predicting and Comparing Protective Behaviors in Germany and Portugal
The Air Quality Matters Podcast in Partnership with
Particles Plus - Eurovent- Aico - Farmwood
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.