Nature and Nurture: The Sustainable Benefits of All-Glass Operable Double-Wall Systems
In the summer, with limited airflow, heat and humidity rise within a building. Just opening a window will not create the airflow necessary to cool a typical office. The all-glass operable system used at Nijverdal involved the placement of two sets of operable walls that can be opened or closed by individual users. The engineers at Nijverdal massed the structure to manipulate the air pressure by creating both the operable Façade as well as designing part of the roof as an airfoil. The open plan of the building allows for easy airflow throughout the structure from wall to wall.
Double-Skin Façades |
Architects have turned to double wall systems as a design solution that allows for increasing the transparency of buildings without reducing energy efficiency. In 1849, John-Baptiste Jobard mentioned a mechanically ventilated double-skin Façade used in Brussels. Architect Otto Wagner won a design competition for the Post Office Savings Bank in Austria in 1903 that incorporated a double skin skylight in the main hall.Double skins can improve indoor air environments and create better acoustic performance in urban settings. Harris Poirazis, a researcher from Lund University in Scandinavia categorizes numerous types of double-skin facades, as follows:
According to Poirazis, an active Façade is a Façade covering one or several stories constructed with multiple glazed skins. The skins can be air tight or not. In this kind of Façade, the air cavity situated between the skins is naturally or mechanically ventilated. In this type of system, devices and systems are generally integrated in order to improve indoor climate with active or passive techniques. There are often semi-automatic controls as part of the system.4 |
Â
Individual users can open either one or both operable window walls to provide direct ventilation. Atrium roofs pitched against the direction of the prevailing winds are fitted with mechanically controlled ventilation windows. Like a wing of an airplane, wind passing over the roof creates negative air pressure drawing air from the building while fresh air flows in through the operable openings. The stack effect caused by temperature differentials in the building causes the air to rise toward the louvers. Air quality is measured using weather data and CO2 sensors. Used air is extracted through controls in the ventilation louvers in the atrium roofs. The corridors that are created between the two glass facades provide solar gain in the winter, and a buffer and solar shade in the summer.
The corridors are the building's lungs, equalizing air pressure as the windows are opened or closed depending on the season on both sides of the building. To prevent drafts the system is monitored by controls and windows are staggered by users. In the winter both sets of operable windows are kept closed and the solar gain from the corridor is vented back through the building to be used as makeup air and by the heat pump. On moderate days, either the interior glass wall or both of the glass walls are open. This provides an opportunity to work on or adjacent to the balcony and closer to the outdoors. Both the framed interior set of windows and the frameless exterior windows open and slide away to provide clear views to the outdoors. During the hottest time of the year, only the exterior walls are open providing a vent for solar gains and creating air differentials for intermittent ventilation through the roof monitors.
 |
The corridors are vented through the balcony flooring. Both sets of windows have high performance glass and are operable. Photo courtesy of NanaWall Systems Inc. |
Notice
