Experimentelle Untersuchung zur Dichtigkeit von Glasleistenstößen bei Aluminiumfenstern unter Berücksichtigung von Behaglichkeitsaspekten

Experimental study on the tightness of glazing bead butt joints of aluminium windows considering comfort aspects.

Step by step, increasingly demanding requirements on thermal insulation and air tightness for the building envelope are set by national Energy Saving Guidance. Blower door test give building owners, users and investors the possibility to check/test the air tightness of their building. This leads to a rise in customer complaints regarding air leakiness and drafts near the windows. Users complain about discomfort at working placed close to the window area. Due to the fabrication technique of the aluminum window and the clipping technology of the glazing beads, small gaps at the joints are unavoidable. DIN EN 12207 [1] limits and categorized the allowable joint permeability related to a reference pressure. State of knowledge based on experience evaluates joint gaps up to 0.3 mm as noncritical concerning joint permeability. However, this does not take into account the assessment on thermal comfort. Measurements carried out at a Façade- and Window Test Center show that all around glass rebate insulation and inner wedge gaskets with flaps can reduce the joint permeability by 15 percent compared to a standard window system without any additional insulation. As a consequence, the air flow rate and the air flow speed will be reduced both directly at the gap and at the occupied area at a distance of 1 m from the window.
The results of the measurements displayed in this edition reinforce the general experience and emphasize at the same time the need to exercise particular care on fitting accuracy of glazing beads. Gaps of less than 0.3 mm on each side of the window and pressures up to 300 Pa are noncritical regarding the comfort of persons in window areas.