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

Chapter 2.0Natural Ventilation2.1 IntroductionNatural ventilation has been used throughout history as a means to ventilate and passively coolstructures. With the advent of more densely populated office buildings, with more computers,higher internal heat loads, and deeper floor plans, buildings have moved toward tighterconstruction, controlling the air introduced into the building, and are generally cooledmechanically. It is the increased heat load and concerns over occupant comfort that often restrictdependence on natural ventilation in commercial office buildings, even in temperate climates.The attainment of uniform internal temperatures for occupant comfort was thought to be possibleonly by controlling amount of air being supplied to an occupied space and its temperature.Although summer conditions are of primary concern related to occupant comfort, attention has tobe paid to the winter conditions to ensure that the building also performs well during periodswith cold external temperatures. During the summer months, the goal is to bring in ventilation tomeet comfort requirements and cool the space using purpose-provided openings. In the winterhowever, any infiltration will add to the cost of heating the space to meet comfort requirements.A well designed and constructed naturally ventilated building should be able to performsatisfactorily year round. The focus of this research is on summer conditions, evaluating theairflow patterns and velocities that can be created by natural ventilation in a commercial officebuilding.This chapter presents the foundation of natural ventilation from the types of ventilation tospecific design elements. First the types of ventilation, buoyancy-driven and wind-driven, arepresented. Then design characteristics included in low-energy and naturally ventilated buildingsare outlined, followed by a brief description of the specific design characteristics that were usedin the prototype building. The method used to evaluate the effectiveness of natural ventilation inthe prototype building is then described, followed by a discussion of factors that are unique tonaturally ventilated buildings.2.2 Types of Natural VentilationThere are two main forces that drive natural ventilation: stack or buoyancy-driven ventilationand wind-driven ventilation. Although these types can be found individually, more commonlyboth are found in naturally ventilated buildings, sometimes with one type dominating the other.In this section both buoyancy- and wind-driven natural ventilation will be defined individually,followed by a description of how they are defined when found together.25