"“Why do we heat and cool buildings with air? How did a thermodynamically and physiologically irrational medium of heat transfer - air - become the dominant method of heating and cooling buildings? 

Water is 832 times denser than air. Energy Density is directly related to the density of a material. Water can capture and channel far more energy per unit volume than air. Thermally active surfaces are built around this basic principle. 

The human body is a hydronic, thermally active surface system. Heat energy is transferred in and around a body through the hydronic circulatory system. The heart circulates heat through the blood back and forth between the core of the body to its skin, a thermally active surface. Its thermal system is decoupled from its ventilation system. 

Thermally active surfaces in buildings follow this logic, literally. This alters energy consumption and amends human comfort. Thermally active surfaces in buildings are not metaphors for the body and do not mimic a natural system. Rather, they share the same thermo-dynamical system. In this century, building science and systems will follow how the body actually functions. 

The human body uses radiant transfer to exchange most of its thermal energy. Buildings based on this logic will significantly amend current patterns of energy consumption and human comfort. 

Achieve greater human comfort with low air temperature heating and high air temperature cooling. Thermally active surfaces utilize low-supply temperature heating and high-supply temperature cooling to achieve human comfort. This can save an immense amount of energy in the next century of building. 

Cooling is a deceptive concept. If a building does not get hot, it does not need to be ‘cooled.’ Thermally active surfaces ‘cool’ by continuously removing heat energy. This is fundamentally different from air based approaches to cooling. If a surface is cooler than the bodies and objects in its space, it is removing heat from those objects and has the effect of cooling. There is no circumstance when the surface temperature should be near or at the dew point temperature to heat or ‘cool’ a space. As such, condensation is not an impediment to thermally active surfaces. 

De-fragment buildings and the building industry. Integrated practices must occur on societal levels in how teams and projects are structured as well as on material levels in the form of simplified, yet higher performing, building systems. 

Thermally active surfaces engender more deeply integrated design of material and energy systems for more robust buildings.

What would change if we heated and cooled buildings with water rather than air? 

Thermally active surfaces stand to advance architecture’s practices and performances: its techniques, technologies, professional and ecological sustainability, budgets, and formal possibilities.” 

-Kiel Moe, Thermally Active Surfaces In Architecture

In this episode of The Building Science Podcast we explore one of the world's most potent and revolutionary technologies - thermally active surfaces, or radiant heating and cooling.