Good daylight entry and maximum heat efficiency 30 January 2020 Back to news index

Good daylight entry and maximum heat efficiency

Natural light plays an important role for our well-being, health and performance. In order to provide interiors with plenty of natural light, buildings are often designed with large glass surfaces. But it is precisely here that there is a risk of significant heat loss. Highly thermal insulating glazing helps, but it also filters out a high proportion of valuable natural light. In buildings with smaller window dimensions, this can have a significant effect. As a result, the building is well insulated, but more artificial light is required as less daylight can enter the building. Impressive results in terms of thermal insulation, solar gains and daylight utilisation can be achieved through a combination of the products ECLAZ® from Saint-Gobain Building Glass and the warm edge spacer bar SWISSPACER Ultimate.

A powerful combination
ECLAZ® is an entirely new generation of Low e coating: Thanks to a newly developed coating technology using Exclusive Laser treatment, ECLAZ® combines best thermal insulation properties with exceptional daylight entry and significant free solar gains. CLIMATOP ECLAZ® is a triple heat insulating glazing that is especially suitable for use in cold climates. In temperate regions, the use of the double glazing version CLIMAPLUS ECLAZ®, which also scores highly thanks to its outstanding thermal insulation and light transmission values, is often sufficient. The warm edge spacer bar SWISSPACER Ultimate eliminates thermal bridges at the edge of the glass efficiently and ensures excellent Psi and UW values. It is one of the most effective spacer bars on the market. In combination with the ECLAZ® low e coating, this opens the door to thermal efficiency, natural daylight entry and solar gains. A comparison using standard window dimensions (1.23m x 1.48m) for a PVC window (frame width 117mm) with double glazing and Standard-Low-E coating and an aluminium spacer bar shows that if the ECLAZ® insulating glazing and SWISSPACER Ultimate are combined, the Psi value is reduced by more than 50 percent, while the UW value falls by up to 10 percent. The total energy transmittance of the insulating glass is at 71 percent and makes an increase of 11 % in DGU (up to 20% in TGU) on free solar energy gains possible.

Better energy ratings for export markets

In countries such as Denmark that have clearly regulated window energy ratings, the use of the ECLAZ® and warm edge from SWISSPACER in thermally insulating glazing often facilitates a jump into an efficiency class that is two levels higher. Window manufacturers who optimise their products in this way have a strong competitive advantage – especially when export markets demand verifiable values. The software tool Caluwin offers a reliable calculation basis for this. CALUWIN is available online at and as an App for iOS and Android end devices from the respective App Stores. It was developed by SWISSPACER and implemented by Sommer Informatik GmbH with technical support from the engineering firm BAUWERK. The calculating engine in Caluwin is certified by ift Rosenheim, and the calculations have been tested and confirmed by various international associations.