"We're also finding that group home companies are increasingly persuading prospective new home owners to use thermally broken products," said a manufacturer representative recently.

He said that his company were quoting Residential Thermal Heart at about a 20% cost premium over standard double glazed Altherm windows and doors and this differential was acceptable to a large percentage of clients who valued the benefits of thermal efficiency and interior comfort and warmth.

With optional low-E glass included in the double-glazed units as a further enhancement, it was possible to have a high performance, fully integrated barrier system that addressed both glass and metal conductivity.

In a typical window configuration, Altherm ThermalHEART used in conjunction with a readily available high-spec, low-E glass offers around 90% better thermal performance over and above standard double glazed products.

Thermal modelling carried out by Altherm gives a good indication of the insulative effects of the ThermalHEART technology. For example, in a room where the air temperature is 21°C and the air temperature outside is a nippy 3°C, the temperature of a non-thermally broken aluminium frame on the inside of the window may typically be around 8°C, a major radiator of cold. For a Thermal Heart frame the inside frame temperature would be a much better 15°C.

Altherm also have available for larger windows and doors the robust Metro Series ThermalHEART range. This is a favourite of designers who want to specify tall doors for aesthetic and functional reasons but also incorporate maximum thermal resistance.

As a final touch to its thermal efficiency programme, Altherm manufacturers are moving towards the introduction of a helpful communications tool to alert prospective purchasers to the energy rating of the windows and doors. The rating systems are the ENERGY STAR administered by EECA, the Energy Efficiency and Conservation Authority, and the WEERS system (Window Energy Efficiency Rating System) that has been adopted by Window Association of New Zealand. These systems are scheduled for introduction in the next few months.