What is Thermal Logic for Domestic Homes ?

To be comfortable over the hot Queensland Summer in a domestic home and allow the air-conditioning to work economically, the following three features must be offered:

Ventilation of the roof cavity using whirly bird or mechanical vents – details as per supplier’s instructions.

Insulation – a low heat retention ceiling insulation– which can offer up to R4 summer insulation.

Circulation of the air in the roof cavity completed by the appropriate number and positioning of the eave or ceiling vents.

Fight the battle against heat retention in the roof cavity during the summer months using all three elements.

The Australian Building Code and the Federal Government recognizes the importance of this approach.

The home builder can legally do what he wishes as far as ventilation and the type of insulation is concerned.

Thermal Logic in a domestic home is ensuring that the air cavity above a ceiling recovers thermally overnight !!. Ensuring that the temperature of the air cavity and the ceiling insulation system is 24 degrees celcius or less, first thing in the morning.

This can be simply checked in a home by :

1. Turning off the air-conditioning for two consecutive hot days (over 30 degrees C)
2. Measuring the temperature near the ceiling from within the house, first thing in the morning after the two consecutive hot days.

A typical early morning temperature is 24 degrees C or less and if the house’s roof cavity is properly designed, the interior room temperature will begin at 24 degrees C or less and during the day will rise to approx. 26-27 degrees C. Most homes in Queensland fail this simple test by recording an early morning temp of around 26 degrees C or more, rising to 29 and 30 degrees C fairly quickly during the morning.

The home with Thermal Logic, will require around $200/summer month for electricity running an air-conditioning unit, while an incorrectly insulated home will require around $500/summer month for running the a/c unit. 

Responsible Design

Some contractors use only Anticon Blanket under the roof while many home builders use insulation batts or cellulose fibre in the ceiling. Most do not use any form of ventilation. All these options comply with the Building Code and B.E.R.S. requirements, but PUNISH the home owner with large, wasteful air-conditioning usage costs. The home owner is not aware of the waste of money involved because he believes the ceiling to be correctly insulated.

The cost difference between an unventilated and ventilated system can mean a cost saving of around $300-400 per summer month of electricity needed to run an air-conditioning unit.

Thermal Logic – involves responsible design

Thermal Logic – involves roof cavities as cool as possible that recover over night to the outside temperature.

Thermal Logic – involves air conditioners under mild loading not required to cool a “burning” roof cavity.

Thermal Logic – involves the insulation system that includes a excellent low heat retention insulation to protect the air conditioning system even on the hottest days.