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HVAC - Natural Ventilation & Infiltration

A. Bhatia, B.E.


Course Outline

Natural ventilation refers to the process of exchanging warm building air for cooler outside air without the use of energy-consuming mechanical devices, such as fans and air conditioners.

With an increased awareness of the cost and environmental impacts of energy use, natural ventilation has become an increasingly attractive method for providing acceptable indoor environmental quality and maintaining a healthy, comfortable, productive indoor climate. In favorable climates, natural ventilation can be used as an alternative to air-conditioning systems, saving 10%-30% of total energy consumption.

This 3-hour course provides an overview of design of natural ventilation systems.

The course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

Upon completing the course, you will understand:

Intended Audience

This course is aimed at Mechanical and HVAC engineers, Architects, Building designers, Energy Auditors, Facility managers, Property & Estate managers, Operational & Maintenance Personnel, and General Audience.


Course Introduction

Natural ventilation systems rely on pressure differences to move fresh air through buildings. Pressure differences can be caused by wind or the buoyancy effect created by temperature differences. In either case, the amount of ventilation will depend critically on the size and placement of openings in the building. It is useful to think of a natural ventilation system as a circuit, with equal consideration given to supply and exhaust. Openings between rooms such as transom windows, louvers, grills, or open plans are techniques to complete the airflow circuit through a building.

Though care must be taken to avoid having a wind tunnel effect in areas of the building; this obviously provides an undesirable effect of an excessively windy environment, especially a problem if paperwork is carried out in the area. The type and placement of operable windows or dedicated air inlets and outlets is critical in directing air into and out of the building so they provide both ventilation and cooling of interior surfaces. Interior spaces should be arranged to ensure that dead-air pockets in occupied zones do not occur. Designs can incorporate atria, internal stairwells, ventilation chimneys and small fans to move ventilation air. Code requirements however need to be understood thoroughly.

Each of these guidelines are defined and discussed in this learning module.


Course Content

The course content is in a PDF file HVAC - Natural Ventilation & Infiltration.

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Course Summary

Natural ventilation is a whole-building design concept. The design utilizes the stack effect and wind pressures to supply outdoor air to building interiors for cooling purposes. When ventilating a building using natural ventilation, two distinct design strategies must be considered - one for the winter and one for the summer. During winter only small air flows for are needed (usually 5-8 l/s per person) but there is the risk of cold air drafts. During the summer, the main challenge is providing enough air flow to give effective cooling. Features of naturally ventilated buildings exhaust vents located high in the building with intakes located low in the building, and open building plans to facilitate air movement.

Natural ventilation reduces energy consumption for fans and mechanical cooling and in most cases gives occupants control over their space. The real advantages of a natural ventilation system are twofold:

As the cost of energy and the likelihood of power failures increase, the natural ventilation systems become more desirable.

Natural ventilation in most climates will not move interior conditions into the comfort zone 100% of the time. Make sure the building occupants understand that 3% to 5% of the time thermal comfort may not be achieved. This makes natural ventilation most appropriate for buildings where space conditioning is not expected. Some designs use mechanical systems to provide outdoor air for occupants but use natural ventilation to provide cooling.

As a designer it is important to understand the challenge of simultaneously designing for natural ventilation and mechanical cooling-it can be difficult to design structures that are intended to rely on both natural ventilation and artificial cooling.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.

Take a Quiz

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.