THE WONDER OF THERMAL MASS

Sustainable House Day was a great success with many people exploring the two inspiring homes that were open for the day. It was wonderful to see so many people from different walks of life genuinely interested in building and living sustainably.

One of the key factors in the efficiencies of the home that Geoff Gibson Homes had open on SHD was the integration of strategically placed thermal mass in the design to help achieve an 8.9 Star energy rating.

We are always trying to improve the environmental outcome of all our constructions, whether that be a bespoke urban cottage or a large commercial building. We are designing and building towards the reduction of the embodied energy of the build and reducing the ongoing operational energy of the individual projects.

To that end the placement of additional thermal mass in many different forms works well in both reducing the initial embodied energy of our construction and the ongoing operational energy of the building.

Materials with a high thermal mass give that substance the ability to absorb, store and release heat

Examples of materials with high thermal mass we can use in our buildings are: rammed earth, concrete, brick, block, stone, Phase Change Materials, and even water.

To get these substances to work correctly, the layout of the design needs to place the thermal mass so it has sun exposure in winter but summer shading. Another important factor is to make sure the material being used for thermal energy storage is thermally isolated from the external temperature changes.

Rammed Earth Walls are constructed by ramming a mixture of selected aggregates, including gravel, sand, silt, clay, and a small amount of cement, into place between flat panels of formwork. Rammed Earth at a density of 2000kg/m3 behaves as heavyweight masonry with a high thermal mass. All other things being equal, a high mass building material such as rammed earth remains close to the 24-hour average temperature, so reducing the temperature fluctuations.

Concrete, with a density of 2240 kg/m3 and usually part of most constructions, can be used very efficiently when correctly shaded and exposed. When the concrete is linked directly to other thermal mass materials you end up with a very large thermal storage working to make your home more comfortable yearround.

Brick with a density of 1700 kg/m3 can be used in a reverse veneer situation within the building, placed on the inside of the insulated external frames throughout the building or as independent feature walls. Geoff Gibson Homes used this method extensively in our 9 Star energy rated “Satori” that was constructed in 2016 on Hume Street in Toowoomba. This particular home was awarded Queensland’s most energy efficient at the 2016 HIA Housing Awards. Phase Change Materials are a recent inclusion in a building designers tool kit. PCMs use the power of phase change to actively absorb and release heat. These ‘phase changes’ help maintain constant, comfortable building temperatures. PCMs shift the warmth of the day into the night and the cool of the night into the day, all the while passively keeping a near constant room temperature. A great advantage of PCMs is their light weight and slim profile.

In an area like the Darling Downs where we have a great diurnal temperature range, a well-located high thermal mass wall or floor can supply a battery of useful thermal storage to make your home more comfortable, without you lifting a finger, or costing you a cent.

If you would like to know more, simply arrange a time to visit me at my Design Centre at 20 Stradbroke Street Toowoomba.

— Geoff Gibson