Methodology for the Evaluation of Natural Ventilation in ... - Cham

Table 7. Prototype Construction by Orientation and U-valueOrientation Façade Type Area, m 2 U-Value, W/m 2 CNorth Brick Façade 82 0.45Glazing 228 2.2South Insulated Panels 82 0.45Glazing 228 2.2East Brick Façade 260 0.45Glazing 100 2.2West Brick Façade 260 0.45Glazing 100 2.2The ventilation of Houghton Hall is a combination of buoyancy-wind driven ventilation and fanassistedventilation stacks. There are seven sets of two windows, each containing a larger and asmaller window, at each floor level on both the north and south façades. Each larger, occupantcontrolledwindow is located one meter above the floor, has a solar shading device located aboveit to reduce direct glare, and has a corresponding light shelf on the interior side of the window todirect sunlight further into the occupied space. All of the windows are overall 1.3 meters in width(without the frame, 1.2m), with the lower windows being 1.1 meter in height (0.9m without theframe) and the upper windows 0.45 meters in height (0.35m without the frame). The buildingmanager controls the smaller upper window, determining when to open or shut it for the season.All of the windows are manually controlled to keep costs low without sacrificing function.The building manager opens the upper windows in the spring when the internal temperatureduring an occupied day has risen above 22ºC. Ideally, the windows would be opened at intervals;beginning with every other vent initially and eventually having all of the upper windows openuntil the fall. The building operation philosophy (Rybka 2002) would have the building managerclose these vents during the day in the springtime so as to not over cool the building and requireadditional heat. However, these windows are difficult to get to and are often opened all at onceand left open, rather than as prescribed in the ideal operation. The occupant- windows are closedat night for security purposes.Part of the building design included the installation of Venetian blinds to reduce the amount ofsolar glare throughout the year. These blinds are controlled by the occupants, and can be drawnup or down, as well as tilted to better control the amount of daylight entering the space.However, the blinds were installed on the upper portion of the frame of the upper window ineach floor. When the blinds are all the way down, these blinds essentially cover the upperwindows, restricting the amount of air that can enter (or exit) the building. Additionally, whenthese blinds are in the down position, they reduce the effectiveness of the light shelves, includedin the building design to reduce the amount of fluorescent lighting required.46