According to the owner, the uPVC windows installed in 1975 have proven thoroughly reliable. During renovation work in 1991, the fifteen year old uPVC windows were therefore left in place, while the existing windows were replaced with uPVC.
Even after fifteen years, the sash rebate seal still functioned correctly and did not appear to have suffered any impairment, although seals were usually changed every ten years. While this is not an expensive process, it was not necessary in this case.
Fifteen years ago in Bernina, Switzerland
In 1976, during renovation work the Albergo Ospizio Bernina, situated at a height of 2309 metres, was fitted with Kömmerling uPVC 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 uPVC 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 uPVC windows.
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 technically and visually.
The rebate seal that is still a sign of progressive technology can clearly be seen here. The two critical surfaces still provide an effective seal that is resistant to driving rain, wind and other weather conditions.
No sign of ageing
On the original tilt and turn fittings even the pivoting point subjected to the greatest wear was still fully intact. All the metal parts, including the screws, were free of any corrosion.
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 were installed. Nevertheless, the test window came through both examinations with flying colours.
Resistance to ageing
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 uPVC. The test pieces die 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.
Kommerling test windows prove that the uPVC retains it's value & resists ageing
One of the two uPVC windows manufactured using Kömmerling profiles was taken to the renowned Swiss research company EMPA immediately following its removal. Kömmerling 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 Kömmerling 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.
Airtight against rain
In order to accurately determine the test figures a different measurement was conducted in a pressurized 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 was as good as new. This also conformed with the findings of other test reports which indicated the excellent condition of the steel reinforcement in the enclosed hollow chambers of Kömmerling uPVC profiles.