Stainless steel: a warmer edge. stainless steel offers a good combination of properties

Several warm edge-solutions have been developed in the last years. To evaluate a warm edge product performance it is necessary to judge not only the thermal properties, but the mix of four requirements:

1). Thermal bridge reduction;

2). Ease of handling and processing;

3). resulting insulating glass quality

and

4). Economic efficiency.

Thermal Bridge Reduction

The heat conduction through spacer bars depends on the thermal conductivity of the material and the spacer's wall thickness. Compared to aluminium spacer bars both can be reduced essentially by stainless steel spacer bars.

Another important point is the reduction of condensation. The formation of condensation will be significantly reduced because of the higher glass surface temperature. Compared with conventional edge sealings the outside temperature may drop 4 to 7 °C and more before condensation occurs, depending on the frame construction, temperatures and humidity.

This helps substantially to avoid wet and mouldy windows.

Processing

Because of its high profile stability stainless steel spacer contributes to the continuous production of insulating glass, as the profile as well as the frames can be handled safely. The austenitic stainless steel is optimised with respect to both thermal and IG-manufacturing characteristics. The profile is able to be bent with our without prefilled desiccant. Heating is unnecessary, as the profile is bent cold, reducing manufacturing time and costs, in comparison with some other warm-edge products. Frames with sharp edges or bows can easily be manufactured.

Stainless steel spacer bars can be cut by abrasive wheels or special thin walled steel sawing blades. Corresponding to aluminium spacers there are no changes in fixing Georgian bars or butyl application.

Insulating Glass Quality

To introduce stainless steel spacer instead of other metal spacer bars, insulating glass producers require no special tests to comply with current quality and test conditions. The positive experience gained with insulating glass with two-stage edge sealing and metallic spacers over the last four decades can be transferred. A metal spacer is and stays impermeable against gas and water vapour for its whole lifetime. The adhesion to sealants has been proved by all major sealant producers with excellent results.

Compared with other spacer materials stainless steel has a noticeably lower difference in thermal expansion relative to the glass. This reduces the sealant stress and has a positive effect on the lifetime of the insulating glass.

Efficiency

The market demands high-quality products at reasonable prices. At minimal costs, less than one part in a thousand of the cost of a building, a substantial improvement in the window units will be obtained by using stainless steel. Insulating glass and windows have a lifetime of about 30 years. In an average single-family house, for example, it will save about 60 litres of heating oil per year. This energy saving corresponds to an annual reduction of around 100 m3 carbon dioxide (CO2) per house.