In 1976, during the course of renovation work the Albergo Ospizio Bernina, situated at a height of 2,309 metres, was fitted with KOMMERLING PVCu windows.

In 1991, the panoramic windows were restored to their historic, former design. KOMMERLING took this opportunity to remove and examine two of the fifteen year old PVCu windows.

This high mountain pass linking Italy and Switzerland experiences uniquely severe weather. Long periods of hard frost, violent storms, an inhospitable climate and increased radiation provided a rare opportunity for long term research into PVCu windows.

This comparison will be of interest to anyone familiar with the way that the cold causes certain plastics to become brittle: the average air temperature at Bernina is 8°C lower than in Zurich. KOMMERLING windows are also resistant to continuous periods of frost.

The global radiation comparison between Zurich (red) and the similar location of Santis (yellow) shows an annual average in Bernina that is a quarter higher, with significant peaks, too. Resistance to ultraviolet radiation is a vital factor in ensuring durability and maintaining whiteness.

After fifteen years of use under the most severe weather  conditions the tilt and turn windows still functioned perfectly. With only minimal care they were still in an excellent condition, both visually and technically.

Even after 15 years, the sash rebate seal still functions correctly and does not appear to have suffered any impairment, although seals were usually changed every ten years. While this is not an expensive process, it has not been necessary in this case.

The rebate seal that is still a sign of progressive window technology can be clearly seen here. The two critical surfaces still provide an effective seal that is resistant to driving rain, wind and other weather conditions.

On the original tilt and turn fittings even the pivoting point subjected to the greatest wear is still fully intact. All the metal parts, including the screws, are free of any corrosion.

One of the two PVCu windows manufactured using KOMMERLING profiles was taken to the renowned Swiss research company EMPA immediately following its removal. KOMMERLING was so confident of the quality of its 1976 windows that the institute was also asked to test for air-permeability and resistance to driving rain in accordance with test category C, still the highest ranking classification. Such confidence was based not only on the condition of the windows being, both in visual and functional sense, but also on comparable tests of older KOMMERLING profiles, which repeatedly demonstrated that their performance matched the requirements in force at the time of their removal, rather than in their installation. This was again confirmed by the EMPA tests: here the windows met the highest performance specifications in terms of their effectiveness of their seals and resistance to driving rain, and complied with the European standards in force since 1991.

The graph showing the permeability of the joints, which in this case is more accurately referred to as the waterproof properties of the seals, shows that the performance of the 15 year old test windows was some 50 times better that that of new windows as specified by the Swiss standard in force since 1991.

For the test windows removed from the Albergo Ospizio in Bernina, colour stability was certainly the greatest challenge. Even the extreme exposure to sunlight and high levels of ultraviolet radiation over a period of 15 years did not result in any noticeable changes to the colour. After basic cleaning, there was virtually no difference between the weathered and the unweathered surfaces of the profiles.

Tests to determine the air permeability and resistance to driving rain were conducted in accordance with the Swiss directives of 1989, i.e. regulations that were only introduced 13 years after the windows had been installed. Nevertheless the test window came through both examinations with flying colours.

A visual assessment of the interior and exterior surfaces of the profiles gave no indication of any adverse ageing effects in the structure of the PVCu. The test pieces did not reveal any cracks, hairline cracks, or discoloured areas or stripes. Together with the other findings such as the absence of corrosion on the steel reinforcement and the good condition of the fittings, it can be assumed that they have lasted very well, exceeding many times over the serviceable life of the windows.

In order to accurately determine the test figures a different measurement was conducted in a pressurised chamber, confirming the airtight properties of the test window. In all three categories the resistance to driving rain clearly fulfilled the current requirements throughout the duration of the tests.

The steel reinforcement is as good as new. This also conforms with the findings of other test reports which indicated the excellent condition of the steel reinforcement in the enclosed hollow chambers of KOMMERLING PVCu profiles.