Green renovating – an expert’s tips, part 4

Locating building materials so that they absorb, store and release heat in all the right places is a aspect of designing an energy efficient home.

While much of Australia still uses brick veneer, it’s actually “completely the wrong way round for comfort” in most southern Australian climactic zones according to architect and solar consultant, Derek Wrigley..

In his book on Making Your Home Sustainable, Wrigley explains where thermal mass should be located and where it can be added to the walls, floors or ceilings to control the temperature inside your home.

Thermal mass basically describes the ability of building materials to store heat. By placing the right types of building materials effectively throughout the house, you can use their thermal mass to absorb, store and release heat so that they keep your home cool in summer and warm in winter.

Using heat from the sun

Wrigley explains that a reversed brick veneer wall (brick on the inside and a lightweight cladding on the outside with insulation in between) would provide better thermal comfort.

However adding extra mass to walls inside your home will only be effective if the room receives direct sunlight for a reasonable amount of time during the day.

“Adding extra mass to rooms on the cooler side of the house would be of little value and a waste of money unless reflectors have been installed, in which case extra mass would be valuable.”

In addition, since we’re talking about renovating here, it’s unrealistic to think that you’ll suddenly go and swap the walls around! So what else can you do?

Here are a couple of simple greenovating options to try.

1. Ceilings

As warm air tends to accumulate in the upper section of the room, the ceiling would be a logical place to add extra mass, which in turn would absorb heat through the day for use at night when the temperature falls.

While the usual type of construction is simple not able to support any significant extra weight, a product known as a phase-change plastic – BioPCM™ - can help absorb and release heat.

Laid under the insulation of a plasterboard ceiling, BioPCM™ absorbs and releases heat using bio-based phase change materials that melt and solidify at room temperature. Unlike other PCM products derived from crude oil refining, BioPCM™ is derived from abundant bio-based materials.

2.Floors

Even if you have a timber floor you could still improve the thermal mass. Add a layer of 25mm compressed fibre-cement sheet [http://jameshardie.com.au/products/hardiepanel.html] to the whole floor and then put tiles on top. This works well if there’s good solar intake through a full-height window for example.

Another option is to insulate uunder the timber floor to reduce heat intake or loss.

Next week: Wrigley’s guide on how to use cross ventilation for indoor climate control.