Technical building components in and around windows Markus Binder
C 3.1
As well as supplying interiors with light and fresh air, one of the primary functions of win dows and facade openings is to let moisture and pollutants out. As construction methods become more technologically advanced, building services are increasingly supporting or even completely fulfilling these functions to more specifically achieve the desired interior conditions and save energy. From a functional perspective, various elements of building ser vices do not necessarily have to be directly connected with windows, but such combin ations are often advantageous. Combining functions can significantly minimise the need to create openings in a facade, which are always costly and complex to construct. Appro priately arranged heating elements and proper ventilation can compensate for comfort prob lems resulting from the typically lower levels of thermal insulation offered by windows and glazing compared with opaque facade elem ents. Lights integrated into facades can sup plement the daylight entering through win dows if required, while window-integrated sen sors and actuators can help optimise building operations by linking them with building auto mation systems. Ventilation and air conditioning A minimum exchange of air is required to ensure healthy, hygienic conditions in build ings and is traditionally provided actively by the opening of windows and passively through leaks in the building envelope (see “Perme ability to air, joint permeability and minimum air exchange rates”, p. 61ff.). The driving forces behind air exchange are differences in temper ature between the interior and exterior and wind pressure on facade surfaces. Since these factors depend on weather conditions, users have only a very limited influence over the exchange of air. High rates of air exchange can occur through joints in older, leaky build ings and cause heat losses and uncomfort able draughts in winter. For these reasons, buildings are now built to be airtight, so the necessary exchange of air must be ensured in other ways. 198
Required supply of fresh air
The volume flow required to supply a space with fresh outside air and release moisture, noxious and malodorous substances depends mainly on the number of people present and their activities. If physical activity levels are low, a supply of fresh air per person of 20 to 30 m3/h can be assumed. Much larger amounts of air may be required to prevent overheating if heat is also released through ventilation. Conversely, a reduced air exchange rate is sufficient outside of utilisation periods if only substances released by structural elem ents and equipment must be discharged. DIN 1946-6 prescribes air exchange rates for housing (see “Permeability to air, joint permeability and minimum air exchange rates”, p. 61ff.). As well as natural ventilation through win dow openings, which depends entirely on users, integrating ventilation components into windows is another way of ensuring a continuous supply of fresh air that meets users’ needs. Passive air vents are openings deliberately made in new buildings in and around win dows, through which air can flow in or out and contribute to the required exchange of air. Built-in ventilators in active, window integrated ventilation devices manage volume flows and can also heat or cool incoming air. The options available depend on where ventilators are installed. Figure C 3.2 provides an overview. Guidelines LU-01/1 and LU-02/1 published by the ift Rosenheim specify the properties of and recommendations for air vents in and around windows.
C 3.1 Facade with integrated ventilation elements, Children’s and Cardiological Centre at the Uni versity of Innsbruck (A) 2008, Nickl & Partner C 3.2 Classification of air vents C 3.3 Soundproofed air vent for installation on a window frame, exterior view C 3.4 Integration of exterior air vents C 3.5 Self-regulating damper, correlation between wind pressure and volume flow C 3.6 Filter classes for ventilation technology in accord ance with EN 779