Allan Daly

Various methods are used to design and operate underfloor air distribution (UFAD) systems. There
are a number of factors that affect UFAD performance: air distribution strategies in the supply plenum, system configuration and diffuser types, slab insulation, air handler supply temperature setpoints, operation of blinds at peak conditions, impact of occupant control, and the effect of climate
differences. Generally, these factors influence performance indicators, such as plenum “thermal… Show more

Various methods are used to design and operate underfloor air distribution (UFAD) systems. There
are a number of factors that affect UFAD performance: air distribution strategies in the supply plenum, system configuration and diffuser types, slab insulation, air handler supply temperature setpoints, operation of blinds at peak conditions, impact of occupant control, and the effect of climate
differences. Generally, these factors influence performance indicators, such as plenum “thermal
decay” (supply air temperature gains) and room air temperature stratification, which in turn affect system energy use and comfort conditions. Previously, the impact of design and operating strategies has been difficult to evaluate analytically due to the lack of simulation tools that accurately model the complex heat transfer processes involved with thermal decay and stratification. The development of EnergyPlus along with the recent addition of the UFAD module has progressed to the point that a systematic comparison of these strategies is now possible. Show less

A thorough investigation of model predictive control for energy efficient buildings with thermal storage

The building sector is the largest energy consumer in the world. Therefore, it is economically, socially, and environmentally significant to reduce the energy consumption of buildings. Achieving substantial energy reduction in buildings may require rethinking the whole processes of design, construction, and operation of a building. This article focuses on the specific issue of advanced control system design for energy efficient buildings.

This project was a simulation study of the energy performance of a prototype three-story office
building configured for both conventional overhead (OH) air conditioning and underfloor air
distribution (UFAD). Both the annual energy consumption and the peak demand were calculated
using EnergyPlus v3.0 for the building in three California climate zones, Los Angeles,
Sacramento and San Francisco. The sensitivity of the energy performance to the building
configuration (e.g.… Show more

This project was a simulation study of the energy performance of a prototype three-story office
building configured for both conventional overhead (OH) air conditioning and underfloor air
distribution (UFAD). Both the annual energy consumption and the peak demand were calculated
using EnergyPlus v3.0 for the building in three California climate zones, Los Angeles,
Sacramento and San Francisco. The sensitivity of the energy performance to the building
configuration (e.g., window to wall area ratio, etc.) and other features of the building was
studied. The main result of the study was that UFAD provides energy savings compared to OH
in all three climate zones, both in terms of annual energy consumption and also in the reduction
of peak demand HVAC annual energy reductions were greater in San Francisco but only
marginally better than in the warmer climate zones of Los Angeles and Sacramento. A second
major outcome of this study was improvements to the UFAD implementation in the recently
released EnergyPlus v3.1. These involved improvements in stratification modeling in interior
zones, addition of perimeter zone stratification models, creation of a whole building template
model, and user documentation to facilitate use of the new capabilities. Finally, the effectiveness
of various demand response actions such as raising the room setpoint temperature and reducing
internal lighting and equipment loads was evaluated. Raising the setpoint temperature was found
to be the most effective measure to reduce peak demand. Show less

Underfloor air distribution (UFAD) is an air-conditioning method that fundamentally differs from the conventional overhead mixing approach found in most commercial buildings. UFAD systems create stratified thermal environments where mixing systems create spaces that have uniform temperatures. UFAD proponents assert that there are many benefits of UFAD over conventional systems, but because the fundamental performance characteristics of UFAD systems have not been well
understood, it has been… Show more

Underfloor air distribution (UFAD) is an air-conditioning method that fundamentally differs from the conventional overhead mixing approach found in most commercial buildings. UFAD systems create stratified thermal environments where mixing systems create spaces that have uniform temperatures. UFAD proponents assert that there are many benefits of UFAD over conventional systems, but because the fundamental performance characteristics of UFAD systems have not been well
understood, it has been difficult to validate these claims.

A research project performed by the Center for the Built Environment and a team of researchers from the University of California, San Diego, Lawrence Berkeley National Laboratories, York International Corporation, and others has undertaken the task to perform fundamental modeling of UFAD systems, validate the models with real-world testing, and create a UFAD energy simulation module for the EnergyPlus software. As a part of this larger context, this thesis project developed and implemented a research and analytical tool to make possible the testing and validation of the UFAD energy simulation module. The tool consists of a flexible user interface to EnergyPlus that manages data input and output and creates summary calculations and graphics.

With the UFAD energy simulation module running and validated, the EnergyPlus interface was used to perform multiple parametric runs in an effort to compare conventional overhead systems with UFAD systems. Results and analysis show that indeed there are significant differences between OH and UFAD system performance characteristics. Some of the results suggest that the asserted energy benefits of UFAD systems may be overstated due to the high amount of heat transfer into the supply plenum that is revealed by these runs. Show less

ISBN 1-931862-21-4

Underfloor Air Distribution (UFAD) Design Guide, co-authored with F. Bauman, ASHRAE, ISBN 1-931862-21-4, 2003.

Despite widespread belief that they waste energy, operable windows can be successfully integrated with HVAC systems

Deep efficiency and zero net energy goals require two profound shifts in thinking about evaluation of building performance. First, performance targets must expand from a limited set of building systems addressed by traditional codes and standards, to an all-systems accounting of energy use. Second, there must be intent to assess performance relative to targets as-operated (measured) in addition to as-designed (modeled). These two shifts need to be accompanied by availability of more measured… Show more

Deep efficiency and zero net energy goals require two profound shifts in thinking about evaluation of building performance. First, performance targets must expand from a limited set of building systems addressed by traditional codes and standards, to an all-systems accounting of energy use. Second, there must be intent to assess performance relative to targets as-operated (measured) in addition to as-designed (modeled). These two shifts need to be accompanied by availability of more measured performance data to support goal setting and modeling.

The University of California, Merced has established a benchmark-based process that successfully achieves these shifts. This paper describes target setting, modeling, and performance validation approaches adopted from the outset by the new campus, including detailed results for one building. Successes and lessons learned in implementing this process can support other building projects on the trajectory toward zero net energy, as well as provide insights for program design, implementation, and evaluation.

The campus implemented comprehensive targets along side traditional standard-based targets. Designers were challenged to do analysis that would not only provide the basis for LEED® ratings and public purpose incentives, but also stand the test of validation by post- occupancy performance monitoring. Some of the first buildings exceeded initial expectations for deep efficiency. A large classroom and office building and a large laboratory use less than 65% total energy and have around 50% of the peak demand of benchmark buildings. This success contributed to the establishment of a whole-campus goal of zero net energy by 2020. Show less

Monitoring Building Performance, Chapter 21 of Time Saver Standards for Architectural Design Data, 7th Edition, McGraw Hill, 1997
 Co-authored with Bill Burke and Cris Benton.