HVAC - Overview of Underfloor Air-conditioning Systems

HVAC - Overview of Underfloor Air-conditioning Systems

Course Outline

Underfloor air distribution (UFAD) turns air supply upside down, allowing a floor plenum to deliver conditioned air to the space via floor diffusers in the raised floor system. It has been tested in various studies undertaken by different agencies that air introduced from a low level offers improved comfort conditions, better indoor air quality in the workspace while offering additional benefits in cost, time and HVAC equipment efficiency.

This 3- hour course is based on research sponsored by the Center for the Built Environment (CBE), an NSF/Industry/University Cooperative Research Center at the University of California-Berkeley and an article "Outlook for underfloor air distribution" published in ASHRAE Journal, 6, 18-25.

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

Learning Objective

At the conclusion of this course, the readers will:

Differentiate between the conventional overhead and underfloor air distribution (UFAD) systems;
Learn the difference between displacement ventilation and hybrid underfloor systems;
Describe the comfort and productivity issues associated with UFAD systems;
Describe the energy savings and indoor air quality improvement with UFAD systems;
Differentiate between the perimeter and internal zones;
Understand the design approach and control strategies for UFAD systems;
Learn the access floor system design and construction issues;
Understand the economics, condensation, dirt and fire protection issues associated with UFAD systems; and
Learn the applications where the underfloor air and access floor systems are most suitable.

Intended Audience

This course is aimed at students, mechanical and HVAC engineers, architects, building designers, contractors, civil estimators, energy auditors, facility managers and general audience.

Course Introduction

In underfloor air distribution (UFAD) system, the conditioned air is introduced through diffusers at floor level and is exhausted at the ceiling through return or relief grilles. The floor plenum typically consists of pedestals and removable floor panels that can be rapidly reconfigured. The space is divided into two zones, an occupied zone extending from the floor to head level, and an unoccupied zone extending from the top of the occupied zone to the ceiling. The systems are designed to condition the lower occupied zone only; temperature conditions in the upper zone are allowed to float above normal comfort ranges. To avoid occupant discomfort, air is introduced into the space between 65°F and 68°F.

The fact that conditioned air is delivered at or near floor level, directly into the occupied zone of the building, and is returned at or near ceiling level do provide energy savings while improving comfort and indoor air quality in many applications. While this strategy is most effective in new construction, it also can work in major retrofits. Thoughtful design is the key to successful application, and often-underfloor air systems are most successful when installed in combination with other energy efficiency measures.

With this brief introduction, this course discusses in detail how the UFAD system differs from the conventional HVAC design and reviews several key design issues pertinent to UFAD design.

Course Content

The course content is in a PDF file HVAC - Overview of Underfloor Air-conditioning Systems . You need to open or download this document to study this course.

Course Summary

Underfloor air distribution (UFAD) is an approach to space conditioning in buildings that has several potential advantages over traditional ceiling-based air distribution systems. UFAD systems have been shown to offer the enhanced level of energy efficiency, comfort, productivity and flexibility. The potential benefits are summarized below:

1) In typical office environments, UFAD systems are able to provide more than three-to-five times the maximum sensible cooling capacity of a comparable displacement system without subjecting occupants to draughts or to an excessive vertical temperature gradient.

2) UFAD systems provide significant energy efficiency advantages due to fan energy savings, extended free cooling and improved chiller COP, thereby reducing life-cycle building costs.

3) UFAD systems offer higher levels of IAQ in the occupancy zone and improved occupant thermal comfort. Unlike displacement systems, UAD systems extend these high levels of IAQ to applications with significant movement and/or heating.

4) UFAD systems provide the opportunity for localized control of airflow and direction, further improving individual thermal comfort.

5) UFAD systems provide flexibility. The ease with which UAD systems can be rearranged to satisfy new office layouts improves flexibility, reducing reconfiguration costs. The modularity of all components of raised access floor systems can be an advantage in space planning, particularly over large open plan areas.

These significant advantages have been recognized in Europe and Japan for several years, where raised floor systems are used in roughly 50% of new commercial building projects. These advantages have largely not been recognized in USA, however growth in the market is steady and UFAD systems can be expected to gain significant growth in years to come.

Quiz

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

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.