Introduction

1.1 Benefits of Ceiling Fans

1.1.1 Thermal Comfort

Thermal comfort is an occupant’s level of satisfaction with the perceived temperature of their surrounding environment. The level of satisfaction is directly related to how much heat is lost from an occupant’s body. Too little and an occupant will feel hot. Too much and an occupant will feel cold. Six factors that affect occupant heat transfer and resulting thermal comfort are described in the American Society of Heating Refrigeration and Air-conditioning Engineers (ASHRAE) Standard 55: Thermal Environmental Conditions for Human Occupancy. These factors are: dry bulb temperature, relative humidity, radiant temperature, air speed, metabolic rate, and clothing level.

Two of these factors are determined by occupants themselves metabolic rate and clothing level. A typical HVAC system directly controls dry bulb temperature in a building. The other three factors (relative humidity, radiant temperature, and air speed) are not directly controlled by the HVAC system but often result by maintaining the space’s desired dry bulb temperature.

When occupants feel hot or cold they typically respond by adjusting the thermostat, as it is often the only means of adjusting the indoor environment. But it is not uncommon for occupants to achieve thermal comfort by using fans and space heater devices that do not significantly change dry bulb temperature but affect thermal comfort. Fans increase air speed, which increases heat transfer from an occupant to the space and creates a cooling effect. Space heaters increase mean radiant temperature by emitting radiant energy that strikes the occupant and creates a heating effect.

This guide will explore how adjusting air speed can impact building and HVAC system design while maintaining the same level of occupant thermal comfort as a typical HVAC system.

1.1.2 Improved Air Distribution

Ceiling fans improve air distribution by increasing the circulation rate of air within a space relative to typical HVAC systems without ceiling fans. Increasing the air circulation within a space has positive effects on HVAC systems by reducing the extent of supply air ductwork, increasing ventilation effectiveness, reducing air temperature gradients, and improving cooling thermal comfort. This has the benefit of simplifying the HVAC system installation and improving its performance.

1.1.3 First Cost Savings

The benefits of improved air distribution offered by ceiling fans can reduce the first cost of HVAC systems in multiple ways. Reducing the extent of the supply air ductwork reduces not only sheet metal costs but also costs associated with reduced system heating and cooling capacity, fewer ductwork accessories, fewer terminals, and lower testing and balancing costs. This has the added benefit of lowering the first cost of the HVAC system where ceiling fans can be incorporated into the building design.

1.1.4 Energy Savings

While it is true that ceiling fans consume energy, the energy saved by reducing the burden on the HVAC system is far greater. This results in a net energy savings for the building. There are several ways that ceiling fans reduce the heating and cooling burden on HVAC systems and reduce energy consumption. They do this primarily by reducing conductive heat losses through the building envelope, improving ventilation effectiveness, and reducing HVAC fan energy.

1.2 Goals of the Guide

1.2.1 Educate

This guide is intended to educate owners, architects, and engineers about why and how to incorporate ceiling fans into building designs. After reading this guide, users should have a good understanding of the science behind thermal comfort, air distribution, and energy consumption. Readers will also understand how ceiling fans can contribute to thermal comfort, improve air distribution, and reduce energy consumption. Furthermore, they will understand how incorporating ceiling fans as a core component of an HVAC system provides more holistic benefits than inclusion as an optional “add-on.”

Users of the guide will learn about the various fan types available and which fan best suits a specific application. Readers will understand how to specify a fan to meet project requirements, and how to evaluate a fan submittal to determine if it truly meets those requirements.

1.2.2 Provide Tools

The guide will provide readers with the tools necessary to effectively incorporate ceiling fans into building designs in a safe, code compliant, and cost-effective manner. These will include guidelines for safe installation, summaries of applicable codes and standards, and resources for assessing the financial implications of a design. Additionally, the guide highlights tools available from Big Ass Fans such as computational fluid dynamics (CFD) analysis and various online calculators.

1.2.3 Give Examples

Examples in the guide will show the reader how to apply their new knowledge and utilize the tools described in the guide in real life applications. Examples will include thermal comfort calculations, fan layouts, system designs, financial justifications, and more. This section will highlight the differences between designing a “standard” HVAC system and an HVAC system with ceiling fans, and compare factors such as layout complexity, energy consumption, and first costs between the two system types.

1.3 How to Use the Guide

This guide has been divided into four chapters: 1) Introduction, 2) Background & Rationale, 3) Applications and Examples, and 4) Case Studies. Chapter 1 introduces the benefits of ceiling fans and the intention of the guide. Chapter 2 will provide background information on the science behind thermal comfort and how to use fans to improve an HVAC design. Chapter 3 contains several examples illustrating the principles described in Chapter 2, as well as more detailed information on specific applications of fans. Chapter 4 features case studies that delve deeper into real-world applications of ceiling fans. The guide has been written in such an order that a user could read it from start to finish and ideally gain a good understanding of ceiling fan systems and applications. The authors also recognize users may wish to jump between sections based on prior knowledge and/or specific project needs. As such, the guide attempts to group and label information in a logical and clear manner, such that users may easily identify areas of interest and read the relevant sections.

As this guide is anticipated to be used by a variety of readers, so too is the information in the guide varied. Owners will find information on operating cost reduction strategies and which building types are well-suited to incorporate fans. Architects will see examples of fan layouts in various spaces and learn about specification options that allow fans to be selected that are well-integrated into a space. Engineers will understand the design decisions that must be made to incorporate ceiling fans into an HVAC design and the impacts fans have on thermal comfort. Overall, the guide aims to paint a full picture of the methods and benefits of ceiling fans to a building design.

1.4 Units Table