The Laws of Thermodynamics and Their Implications on Thermal Comfort in the Built Environment

The Second law of thermodynamics is the most prevalent for the explanation of heat uses within dwellings; it describes the natural direction of energy transformation and entropy. Energy “…move[s] from a highly ordered state to a disordered state…” (Cleveland, Kaufmann 2008.) Heat, as the form of energy with the most entropy, is the eventual natural result; “Entropy of a closed system increases (more exactly, does not decreases) with time.” (Prisyazhniuk, 2007.) This heat will spread until it reaches equilibrium. Within buildings this means that a source of heat, whether it be a fire, hot water system or direct solar gain will spread itself from the concentrated source point out towards any cooler area. Ideally for thermal comfort this heat energy, once within the space should be conserved, emphasizing the importance of airtightness and insulation in design as well as the importance of space economy, or: not wanting to spend the energy to heat to near equilibrium a large space, for just one person. The second law also describes how in order to produce a useful lower entropy, (highly ordered,) form of energy; the kind needed in order to generate heat within our home, that additional energy has to be applied and work done. (Prisyazhniuk, 2007.)  “…the continuous flow of oil, coal, and other fuels used to run society is converted into low quality, unavailable energy ("waste heat").” Also described by the ‘Zero’ law, “…All bodies acquire the temperature of the environment…” (Prisyazhniuk, 2007.)[1] Such laws explain the difficulty of conserving and storing energy as heat, a continuous battle against natural physics that appears to be one of the main elements of environmental dwelling design. We try to harness the high entropy form of energy to store for times when the natural pulsing environment has spread the availible warmth to near equilbrium at a localized area, working with these rules and using the importance of temperature difference to control passive heat flow we endeavour to slow the enevitable directional movement of energy for our comfort.

---

[1] The "Zero" Law of Thermodynamics: the Law of Heat Equilibrium, this wording is put by J. Black (1728 – 1799): "All bodies freely communicating with one another and not subject to a non-equilibrium impact of the ambient conditions acquire one the same temperature, as determined with the thermometer. All bodies acquire the temperature of the environment."(Prisyazhniuk, 2007.)