Thermal Mass on a diet

  • Building Design Expert
  • 5 years ago

People who truly have not had their lives touched by technology are probably designated to reside in a central area of South America, and undiscovered by their outside world. Similarly ‘Thermal Mass’ was a term reserved for construction where ‘Mass’ was the operative word, and ‘Thermal’ was something that crept in once we began to understand the physics associated with the way it functioned. Today even such ancient forms of construction are not immune from corruption by technology.

We now understand that thermal mass operates in a quiet back water of its own, and have adapted the construction form from what was largely ‘massive stone wall construction’, into something a little more manageable, and of course less expensive. No fuss, and no slave to digital tech., as long of course as all the pieces of its particular jigsaw are firmly in place. Requiring a high thermal conductivity, it will happily absorb heat energy thrown at it like a proverbial sponge. Highly insulated on the outside, once the internal temperature drops it doesn’t give a second thought to releasing the stored energy back to where it came from. Even in our high tech digital age, it’s good to see such simple and natural technology in operation.

Enter the digital age: Phase Change Materials (PCM) have been around for a few years now, but like any radical sideways steps, have had to prove themselves in very small increments.

So what is, or are Phase Change Materials? In its simplest form it can be innocuous as a cube of ice. Don’t think about the ice cooling your drink, instead think about your drink heating up the ice. We may appear to be dealing in semantics, but the difference is important in ‘phase change’ terms. The phase change occurs in the transition of the ice from solid to liquid, brought about by the input of energy courtesy of the drink. Okay then the tech is fairly simple – Still.

If we apply the same principle to some microscopic hollow glass beads whose internal void has been filled with wax, incorporating them in a familiar every day material such as plasterboard, we have wghat amounts to ‘nano-technology’ achieving a very similar effect.

The manufacturing tolerances of the wax filled beads are of course supremely fine. But when we are dealing at this level you won’t be surprised to learn that the wax has been chemically programmed to melt at a pre-determined temperature; – let’s say 23ºC. The melt is our phase change. The wax absorbs the heat energy given to it as a result of the ambient internal temperature. Remaining in a liquid state it holds that energy until the temperature drops, releasing it as heat as it changes back to solid form.

It shouldn’t need saying, but I will anyway: The principles of energy release under the heading of thermal mass still strictly apply. For all the ‘highs’  attributable to this technology, the efficiency of energy release is not helped by installing this plasterboard behind fitted furniture , or in small room areas where it will not be effective.

The release of heat is on a relatively small scale so uninterrupted ceilings can generally provide an even distribution of available heat

To remind ourselves, the release of latent heat, by its very nature, needs to be on a reasonably large and uninterrupted scale. That’s large in terms of relative area in relation to the internal space, and uninterrupted in physical terms, so any heat can be allowed into that space. So if we cannot install this material onto a wall, there is no reason it cannot form a ceiling. With a clear ceiling there is an uninterrupted radiant heat source, so that works. The potential for liberation of heat via conduction / convection may depend on how the building designer manages the design / installation. Raking soffits / ceilings are going to offer the liberation of more heat in this way, but too steep an angle may reduce the radiant effect. So trial and error to seek that happy medium. No one size is going to fit all, not when we dealing in fractions.

Phase Change Materials constitute thermal mass on a diet. Simple principles applied to incredible technology that just works.


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