The purpose of this capstone project was to (1) design a cost-benefit analysis system to compare UFAD and traditional HVAC alternatives, (2) test the proposed cost-benefit analysis system through an independent samples t-test comparing the cost-benefit structure of UFAD projects with traditional HVAC projects, and (3) understand the factors that allow UFAD to work as intended in real-world settings.
UNDERFLOOR AIR DISTRIBUTION (UFAD) AND RAISED ACCESS FLOORING: A COMPARATIVE MODEL FOR COMMERCIAL BUILDING OWNERS AND FACILITY MANAGERS IN THE SAN FRANCISCO BAY AREA TO SUSTAIN COSTS IN ENERGY AND MAINTENANCE C A LIFO RNIA STATE UNIVERSITY EAST BAY DEPARTM ENT O F ENG IN EER IN G A M aster’sProject Subm itted by Leah E llen N adel To the D epartm entO fEngineering In partialfulfillm entofthe requirem ents For the degree ofM aster ofScience C onstruction M anagem ent C alifornia State U niversity E astBay H ayward, California June 2013
Transcript
UNDERFLOOR AIR DISTRIBUTION (UFAD) AND RAISED ACCESS FLOORING: A COMPARATIVE MODEL FOR COMMERCIAL BUILDING
OWNERS AND FACILITY MANAGERS IN THE SAN FRANCISCO BAY AREA TO SUSTAIN COSTS IN ENERGY AND MAINTENANCE
CALIFORNIA STATE UNIVERSITY EAST BAY
DEPARTMENT OF ENGINEERING
A Master’s Project
Submitted by
Leah Ellen Nadel
To the Department Of Engineering
In partial fulfillment of the requirements
For the degree of Master of Science
Construction Management
California State University East Bay
Hayward, California
June 2013
Presentation Agenda Overview Of Underfloor Air Distribution (UFAD Purpose Of my Capstone Chapter One: Introduction to UFAD
• Research Questions
Chapter Two: Literature Review• Types of UFAD• Lifecycle Cost Analysis (LCCA)• Case Study SF PUC• Commissioning
Underfloor Air Distribution (UFAD) is an HVAC method in which the goal is to deliver air to an underfloor plenum, air that is subsequently distributed to a space through the use of active and passive floor diffusers. Nonresidential ACM Manual (California Energy Commission, 2008)
1. Design a cost-benefit analysis system to compare UFAD and traditional HVAC alternatives
2. Test the proposed cost-benefit analysis system through an independent sample t-test comparing the cost-benefit structure of UFAD projects with traditional HVAC projects, and
3. Understand the factors that allow UFAD to work as intended in real-world settings.
Chapter One: Introduction
Buildings are both a significant cause of, and a potential solution to, climate change and energy uncertainty (Chance, 2012; Hupp, 2010).
In the United States, buildings consume nearly 40% of the country’s
energy
Responsible for almost 40% of greenhouse gas emissions
This figure represents 8% of the world’s greenhouse gas emissions,
an amount equal to the emissions from all of India
(Hupp, 2010).
UFAD is becoming more popular throughout the United States
It has proved to be cost-effective for many adopters
It is in alignment with principles of green building that are becoming pervasive (Montgomery, 2009).
However, in the absence of a sound cost-benefit analysis structure for UFAD, potential UFAD adopters can neither make truly informed decisions about flooring choices nor, having already chosen UFAD, understand how to reduce the cost of a UFAD system over its lifecycle.
As a result, it is likely both that much money is being wasted and
that many suboptimal raised access flooring designs are being chosen (Lee, Schiavon, Bauman, & Webster, 2012).
Businesses faced with the choice of UFAD versus traditional HVAC still have difficulty in conducting cost-benefit analyses of UFAD.
First, there is limited literature on how to calculate the lifecycle cost of UFAD (Schiavon, Lee, Bauman, & Webster, 2011).
Second, there are a number of possible scenarios that can alter lifecycle cost—for example, a high degree of churn can lower the lifecycle cost of UFAD (Xu, Gao, & Niu, 2009).
Third, there is inherent complexity in modeling the tradeoff between UFAD’s energy-related benefits and lifecycle costs (Xu et al., 2009).
Businesses have often chosen or rejected UFAD on the basis of inaccurate or incomplete calculations (Xu et al., 2009).
CHURN is one of the important factor when designing for UFAD
Churn rate can also describe the number of employees that move within a certain period. For example, the annual churn rate would be the total number of moves completed in a 12-month period divided by the average number of occupants during the same 12-month period.
Monthly and quarterly churn rates can also be calculated.
Formula:
Attrition rate (%) = Number of employees resigned for the month/(Total number of employees at the start of the month + Number of employees joined for that month - Number of employees resigned) x 100
Research Questions
1. Which energy efficiency, lifecycle cost etc. need to be included in a UFAD cost benefit analysis?
2. Do UFAD projects outperform non-UFAD projects, with consideration of both cost and benefits?
a. This question will be answered by means of an independent sample t-test conducted on the basis of the cost-benefit analysis model recommended through the first research question.
b. An independent samples t-test will be used to compare the mean performance of UFAD projects to the mean performance of non-UFAD projects, at an α of .05.
3. What are the best ways to configure and approach UFAD projects, based on quantitative and qualitative information collected?
Chapter Two: Literature Review To describe and evaluate the basic components of UFAD
To relate UFAD and HVAC in general to the various building codes and standards current in California
To describe and evaluate the components of lifecycle cost as they apply to UFAD.
Provides a necessary overview of UFAD.
Explains the relevance of UFAD within the larger system of green building codes operative in California.
Prepares the ground for the generation of a UFAD cost-benefit model that is supported by the literature.
The main types of UFAD systems:
Type 1 UFAD: Interior swirl (passive) diffusers: This system is configured with swirl diffusers in the interior spaces where the airflow is modulated by varying the pressure in the supply plenum in response to interior thermostats, and variable speed fan coil units in the perimeter typically supplying linear bar grille diffusers.
The main types of UFAD systems:
Type 2 UFAD: VAV diffuser:
VAV diffuser throughout—This system consists of controlled damper / diffusers in both interior and perimeter zones. The supply plenum pressure is held constant. A constant speed fan coil is used for heating only, typically in the perimeter.
Caution: HumidityCondensate pans are at lowest point on a floor!Disturbing stratification with high air flows.
Diffuser Types
Swirl Diffusers:Typically used in the interior of the space.
Linear Diffusers:Typically used around the perimeter of the space.
Zoning for UFAD
The various spatial zones are defined both by different floor diffuser types, and a variety of access floor surface finishes.
Lifecycle cost analysis (LCCA) is a process that can help facilities managers understand exactly what UFAD will cost over its lifetime and ensure that a product chosen will meet the needs of a facility. Lifecycle costs also give facilities managers a picture of the energy cost options being considered.
Components of Lifecycle Cost Analysis: Ductwork Installation of Electric Services Cable Management Costs Fan Energy Use Chiller Efficiency Complaint Costs Churn Cost
Case Study: San Francisco Public Utilities Commission
It is estimated that SFPUC will enable a lifecycle cost savings of $118 million over the next 75 years (Perl, 2011).
However, it is not clear what percentage of these cost savings can be ascribed to UFAD.
It is partly for this reason that it is necessary to apply an UFAD-specific cost-benefit analysis to learn more about the advantages of UFAD.
Commissioning
The Term “Commissioning” is adopted from the US Navy’s quality assurance approach for all new and or repaired/updated ships.
The US Navy commissions ALL their ships to ensure they run as smoothly as designed. Building commissioning takes the same approach to new buildings
When a building is initially commissioned it undergoes an intensive quality assurance process that begins during design, and continues through construction, occupancy, maintenance and operations.
Commissioning ensures that the new building operates initially as the owner intended and that building staff are prepared to operate and maintain its systems and equipment.
A full explanation is within body the thesis
Chapter Three: MethodologyRQ.1 Which energy efficiency, lifecycle cost, and other variables ought to be included in a UFAD-centric cost-benefit analysis?
Variable Description Quantification First costs
Added costs for raising the floor
$ per square foot
Ductwork Materials and installation costs for ductwork $ per square foot
Installation of electric services
Materials and installation costs for electrical services
$ per square foot
Cable costs Costs of managing cables $ per worker
Fan energy use Amount of energy spent by fans Joules / square foot
First costs ($ per square foot); continuous variable Ductwork ($ per square foot); continuous variable Installation of electric services ($ per square foot); continuous variable Cable costs ($ per worker); continuous variable Fan energy use (joules per square foot); continuous variable Chiller (% added efficiency); continuous variable Complaint costs ($ per service call); continuous variable Churn cost ($ per worker); continuous variable
Variables in the Study RQ-2
RQ2: Taking both costs and benefits into account, do UFAD projects outperform non-UFAD projects?
UFAD-Related Survey Questions for Engineers
Quantitative Questions (5-Point Likret Scale) Qualitative Questions 1. I have experience with the UFAD design process. 2. The UFAD design process is complex. 3. The UFAD design process is time-efficient compared to the design time of traditional HVAC. 4. The UFAD design process is more cost-effective than traditional HVAC. 5. The industry design specifications of UFAD systems are standardized. 6. The UFAD design process was successfully completed for my installation. 7. The UFAD system requires extensive client education. 8. The UFAD system requires more education of building engineers than traditional HVAC. 9. The building engineer should be included in the design process for UFAD. 10. The construction of UFAD systems is simpler than traditional HVAC. 11. The construction industry understands UFAD. 12. The purchase and installation cost of the UFAD system was less than traditional HVAC. 13. The maintenance of UFAD systems is simpler than traditional HVAC. 14. The maintenance cost of UFAD systems is less than the maintenance costs of traditional HVAC. 15. The UFAD system functions as designed. 16. The failure rate for UFAD systems is less than traditional HVAC. 17. The UFAD system is energy-conserving as compared to traditional HVAC.
1. When specifying UFAD systems, did you find a need to educate your client? Staff? And is there a need to re-educate the AEC industry? 2. How can the engineer assure building owner that UFAD systems perform in accordance with specified design intent? 3. Failures do occur with the design of UFAD. Where do you see the biggest mistakes being made today? 4. If the events were good or bad, what were they? (What is your best experience with the design)?
Designed To Answer RQ-3
Cost-Related Data for Building Managers
Questions 1. If you had a UFAD project, what were the added costs for raising the floor? 2. What are your annual materials and installation costs for ductwork? 3. What are your annual materials and installation costs for electrical services? 4. What are your annual costs of managing cables? 5. What is the annual amount of energy spent by fans? 6. What is your cumulative chiller efficiency? 7. What are your annual costs of responding to complaints by facility occupants? 8. What are your annual costs of relocating a worker from one location to another 9. What is the square footage of your building? 10. How many workers are in your building?
Chapter Four: Findings
UFAD-centric cost-benefit analysis should include:
Added costs for raising the floor Materials and installation costs for ductwork Materials and installation costs for electrical services Costs of managing cables Amount of energy spent by fans Added chiller efficiencies Costs of responding to complaints by facility occupants Cost of relocating a worker from one location to another
The purchase and installation cost of UFAD was less than traditional HVAC
11 1 4 2.36 1.027
The maintenance of UFAD systems is simpler than traditional HVAC
11 2 4 3.09 .831
The cost of maintenance for UFAD systems is less than that of traditional HVAC
11 2 4 3.55 .688
The UFAD system functions as designed
11 2 5 3.45 .820
The failure rate of UFAD systems is less than that of traditional HVAC
11 2 4 2.91 .539
UFAD conserves more energy than traditional HVAC
11 2 5 3.55 .820
Selected Descriptive Statistics, Engineers with High / Very High UFAD Experience
N Minimum Maximum Mean Std. Deviation
The UFAD design process was complex 4 4 4 4.00 .000
The UFAD design process is time-efficient compared to the design time of traditional HVAC
4 3 4 3.75 .500
The UFAD design process is more cost effective than traditional HVAC
4 4 5 4.25 .500
The industry design specifications of UFAD systems are standardized
4 3 4 3.25 .500
The UFAD design process was successfully completed for my installation
4 3 5 3.50 1.000
The UFAD system requires extensive client education 4 4 5 4.50 .577
The UFAD system requires more education of building engineers than traditional HVAC
4 4 5 4.25 .500
The building engineer should be included in the design process for UFAD
4 4 5 4.75 .500
The construction of UFAD systems is simpler than traditional HVAC
4 3 5 4.00 .816
The construction industry understands UFAD 4 3 5 3.75 .957
The purchase and installation cost of UFAD was less than traditional HVAC
4 3 4 3.50 .577
Chapter Five: Summary & Conclusion
The findings of the study suggested that UFAD is, when designed and implemented correctly, a superior alternative to traditional HVAC, at least in California’s climate. UFAD is associated with greater cost savings, convenience, and conformity to California’s emerging green standards.
Summary of Findings
There were significant differences between UFAD and traditional HVAC in terms of (a) cable management (b) fan energy and (c) churn cost
The differences between UFAD and traditional HVAC in terms of (a) ductwork, (b) electrical services , and complaint response were not significant at an α of .05.
UFAD’s mean added costs for raising the floor were $6.40 per square foot
On a square foot by square foot basis, UFAD costs $7.9373, while traditional HVAC costs $9.0013; UFAD thus represents a lifecycle cost savings of $1.064 per square foot.
More Findings
Overall, engineers described UFAD as complex, suggested that UFAD had very slight cost and time advantages over traditional HVAC, and suggested that higher levels of building engineer education and participation, as well as higher levels of client education, were necessary for successful UFAD projects
More Findings
Engineers with higher levels of UFAD experience agreed with the proposition that UFAD was more expensive and complex, but were emphatic in claiming that UFAD: Conserved more energy, failed less frequently Functioned as designed Cost less to maintain and was simpler to maintain Engineers with higher levels of experience were more
adamant about wanting to include the building engineer in the design process and acknowledging the need for more client education
More Findings
In order to be effective, UFAD must be designed and implemented well, which can be a particular challenge when dealing with high-load exterior zones.(location and climate)
Recommendations
UFAD education opportunities should be provided more frequently, both by ASHRAE, AIA and other parties
Building engineers should be included in the UFAD design process as early and intensely as possible
Client education should be a priority for engineers Building engineers should also keep adding to their
store of UFAD knowledge UFAD adoption should be driven by the kind of
cost-benefit analysis modeled in this study
Recommendations
These recommendations can be used by all professions—engineers, building owners, regulatory personnel, and others—in order to ensure that UFAD deployments are well-designed, well-implemented, and cost-efficient, thus resulting not only in monetary savings but also in compliance with the green HVAC standards that are proliferating throughout California and the United States.
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