Energy Efficiency

A recent presentation at the FRAME Australian Conference by Bernard Hockings outlined some interesting thoughts on Energy Efficiency. He described the challenges of Lightweight (Light Framed) buildings in particular:

The heat loss and gain through windows can be 2-5 kW and that he considered that double glazing will start to become more popular. This might also be influenced by small blocks and loud singing in the shower next door.
The impact of mass acting as a heat bank and absorbing energy in both a positive and negative way. The old brick feature wall does more than just add feature.
Elevated floors can cause significant heat loss and gain. For example the heat loss in winter from slab on ground can be nearly four times less than in an elevated house, see Diagram 1. Diagram 2 shows the impact of filling in around the sub-floor and the almost 50% reduction in heat loss. Similar heat gains are saved in summer.
Wall frame thickness was also discussed showing the benefit of a 90 mm frame in being able to install R2.0 batts in comparison R1.5 batts in 70 mm framing.
Design should allow for the fact that there will be condensation and that it needs to go somewhere. Condensation will form when there is more than a 60 difference in temperature. This is particularly important where non-perforated foil is used or where moisture can run down a rafter. The end result of poor design is rotting timber in 10 years.

The future will see energy efficiency of design becoming more important. Apparently the 5 Star system actually goes to 10 Star, although the benefits of going to Six Star only provide a further 6% improvement in energy efficiency. Things like moving to 90mm framing and adding R2.0 Batts may however allow the inclusion of a feature to the design that draws a potential owner to the home. The benefits of the additional insulation may be a trade off that allows the feature.

Diagram 1 - The impact of open raised sub floor in winter

Diagram 2 - The impact of filling in around the sub floor in winter

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