Comfort - does it have to be so boring?

No question this is the most comfortable home we have lived in but I still struggle to get my head around the lack of doing something -anything to adjust - this is boring! The thermometer just doesn't move significantly, the CERV2 data logging is charting flat lines of temperature. I have looked for and can't find cool spots, draughts or even condensation in even our most adverse winter conditions.

We have conditioned ourselves to fiddle with the thermostat and worry about the humidity but in reality, there is much more to it. One of the many benefits of passive house design is that comfort is built right in. So what are these factors that passive house design accounts for? Turns out that while the solution appears simple, the science is complex.

The basics of thermal comfort

Thermal comfort is a subjective state. It is both psychological and physiological, and as such is one of the most complex but important aspects of building design.

There are three types of heat transfer: conduction (transfer through direct contact with solid materials, like holding a hot cup of coffee), convection (transfer through liquids and gasses, like feeling colder when it’s windy) and radiation (transfer through electromagnetic waves, like feeling hot when close to a fire).

In addition, there are six factors that influence thermal comfort:

1. Air temperature: the temperature of the air in the space. This is the factor most think of when considering comfort (it’s too hot, too cold or just right).
2. Humidity: the moisture in the air. With higher humidity, perspiration evaporates less efficiently, resulting in a given air temperature feeling warmer.
3. Mean radiant temperature: the perceived temperature in an environment, created by the average of the air temperature and radiant temperature of all facing surfaces. Mean radiant temperature explains why it can feel cold in the winter adjacent to a large window, even when the room is heated to a “comfortable” 72ºF air temperature. The cool window surface radiantly cools your body.
4. Air speed: the rate of air movement. With higher air speeds (more air movement, within limits), we perspire more efficiently and increase convective heat loss, resulting in a given air temperature feeling cooler.
5. Metabolic rate: the rate of transformation of calories into heat and mechanical work by metabolic activities within an organism. This is directly related to activity level in an environment. With lower levels of physical activity, warmer air temperatures are necessary for comfort, as well as the converse.
6. Clothing insulation: the increased resistance to sensible heat transfer obtained from increasing the amount of clothing. Increasing the amount of clothing insulation decreases the air temperature that is comfortable.