ABSTRACT

A discussion of the thermal properties of thick wall construction with particular reference to the heating and cooling effect of earth walls during a 24-hour period of temperature changes

This paper looks at the ways in which a thick wall behaves as part of a building subjected only to the temperature swings of the outside air. Firstly it discusses the way in which a wall of solid heavy material and relatively high thermal mass responds to ambient temperature changes, tending to dampen both the rate of change and the total swings in temperature. Secondly, a simplified analytical approach will be offered which can yield some useful rules of thumb to predict the temperatures of surfaces and interior mass at different points in the diurnal cycle. While not being a mathematical presentation, this discussion can usefully go further than the anecdotal, non-quantitative approaches commonly found.

We will also look at the ways in which such a wall behaves during shorter periods – an hour or so – and longer – a week or a season, and see how different climates can would make the thermal behavior more or less beneficial to human comfort.

Consideration will be given to how the thermal behavior affects the apparent insulating value of the structure as a result of the thermal dampening. There will also be discussion of how the apparent temperature of the surfaces at different points in the thermal cycle impacts human comfort sensations in the absence of other heating and cooling impacts. Suggestions will be offered not only on how to predict the thermal behavior of mass earth walls in a rational way, but how to enhance and make use of their special thermal attributes.