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

considered when determining how the building operates, including occupant controlled windowsand environmental conditions that are available as resources to control building performance.The building data also were used to verify numerical simulations, using computational fluiddynamics software, scaled physical models and other design tools.The methods used in evaluating the prototype building are described in the following sections.2.4.1 Thermal PerformanceSeveral factors contribute to the thermal performance of a building; building construction,interior loads and space temperature, and air movement. The building fabric can have significantimpact on the thermal performance of a building in terms of both thermal conduction throughexterior walls as well as passive heating and cooling strategies. Buildings that have moreexposed thermal mass, i.e. are ―thermally heavy‖, can retain heating or cooling energy better,and for longer periods, than ones that are thermally light, with less thermal mass. The overalltemperature within a space and the amount of vertical temperature stratification within the spacecontribute to the thermal comfort and performance of a building.Internal loads impact the interior temperature of a given space. People, equipment, and lightingare typical interior loads that contribute to the cooling load due to the heat that they emit. Thedensity or number of units per floor area of these interior loads determines the heat load for thespace. Office buildings typically have 10-15 square meters per occupant and 75-120 Watts peroccupant. Lighting loads can vary between 12-20 Watts of energy use per square meter in acommercial office building. The ancillary equipment loads, including computers, monitors,printers, etc. typically contribute 10-18 Watts per square meter. These internal loads, and theheat that they generate, contribute to the increase in temperature in the interior environment,which then has to be removed through ventilation, natural or otherwise. Air movement, notventilation specifically, contributes to thermal comfort of the occupants within a space. Comfortstudies have found that the warmer the interior temperature, the higher the acceptable indoor airvelocity for comfort of occupants (Daniels 2003).2.4.2 Ventilation PerformanceWhen evaluating ventilation effectiveness, the path of the air from entry to exit point must beconsidered. This is done on a macro and a micro scale; both global air flow into and out of thebuilding and at a more detailed level, space by space. The method in which the air is introduced,travels through, and is exhausted from individual spaces and the building as a whole contributeto the ventilation performance and effectiveness of the building. For mechanically ventilatedbuildings, this evaluation generally means focusing on the heating, ventilation, and airconditioning(HVAC) system. As the entry and often the exhaust of air both into and out of thebuilding and individual spaces is controlled, this tends to be a straight forward procedure.Though there are often many components that make up the system that conditions the building,these components are often monitored and controlled by a building management system toensure proper operation and occupant comfort.Since the inlet and outlet points for a mechanical system are specifically designed and detailed,the methods to measure ventilation performance are well defined. Duct traverses, filterconditions, various system set points and dampers are some of the items assessed whendetermining ventilation effectiveness of a ventilation system and conditioned space. However,36