Mccoy Ufad 080806

Fred Bauman, CBE 1

Designing UFAD Systems: Updated Guidelines August 8, 2006McCoy UFAD Workshop

Designing Underfloor Air Distribution (UFAD) Systems:

Updated Guidelines

McCoy Specialty ProductsHouston, TexasAugust 8, 2006

Fred Bauman, P.E.Center for the Built Environment, University of California, Berkeley

2

Acknowledgments

Taylor EngineeringAllan Daly

Pacific Gas & Electric Co.

ASHRAE

Course Development

Projects, ImagesArup, Flack + Kurtz, Halton Company,Nailor Industries, Price Industries, Tate Access Floors, Titus, York International

3

Agenda

8:15-8:45 Introduction 8:45-9:45 Diffusers and Stratification9:45-10:15 Comfort and IAQ10:15 -10:30 Break

10:30-11:25 Underfloor Plenums11:25-11:40 Horizontal and Vertical Distribution 11:40-12:00 Demo of McCoy UFAD Showroom12:00 -1:00 Lunch

1:00-1:45 Load Calculations, Energy1:45-2:15 Commissioning and Operations2:15-2:30 Post-Occupancy Evaluations 2:30-2:45 How to Decide to Go with UFAD?2:45-3:00 Wrap-Up, Conclusions3:00 -3:15 Break

3:15-4:00 Questions/Open Discussion

Introduction

8:15 – 8:45

5

CBE Organization

Industry/University Cooperative Research Center (I/UCRC)

National Science Foundation provides support and evaluation

Industry Advisory Board shapes research agenda

Semi-annual meetings emphasize interaction, shared goals and problem solving

6

CBE Industry Partners

Armstrong World Industries

Arup*California Department of

General Services

California Energy Commission

Charles M. Salter Associates Flack + Kurtz, Inc.

HOK

Pacific Gas & Electric Co.Price Industries

RTKL, Associates, Inc.Skidmore Owings and MerrillStantec

Steelcase, Inc.Syska Hennessy GroupTate Access Floors Inc.*Taylor Engineering Team:

• Taylor Engineering• CTG Energetics• Guttmann & Blaevoet• Southland Industries• Swinerton Builders

Trane U.S. Department of Energy (DOE)*U.S. General Services Administration (GSA)*

Webcor Builders*York International Corporation

*founding partner

Fred Bauman, CBE 2


7

CBE UFAD Research

CBE’s research program on UFAD systems has an annual budget of ~$500K studying the following topics:

Energy modeling

Room air stratification

Underfloor plenum performance

Field studies

First and life-cycle cost model

Design and commissioning guidelines

Technology transfer

8

Overhead System

55°F-57°F

9

Underfloor air distribution system

60°F-65°F

10

Potential UFAD Benefits

Improved occupant comfort, productivity and health

Improved ventilation efficiency and indoor air quality

Reduced energy use

Reduced life-cycle building costs

Improved flexibility for building services

Reduced floor-to-floor height in new construction

11

Underfloor vs. Conventional Air Distribution System Design Issues

Underfloor air supply plenum

Air supplied into occupied zone near floor level

Higher supply air temperatures (for cooling)

Allows for occupant control

Properly controlled stratification leads to reduced energy use while maintaining comfort

Reduced space sensible heat load

Perimeter zone solutions are critical

Access floor improves flexibility and re-configurability

12

Current Barriers to UFAD Technology

Lack of familiarity by building industry

Higher first costs

Need for design guidelines and tools

Fundamental research needed on key issuesRoom air stratification

Underfloor plenums

Energy performance

Thermal comfort and ventilation effectiveness

Problems with applicable standards and codes

Fred Bauman, CBE 3


13

Room Air Stratification(cooling operation)

14

Floor Construction

15

Integrated Service Plenum

16

Underfloor Air & Power

PLUG & PLAY POWER and CONTROLS

Modular Wiring

VAV

Diffuser

17

Underfloor HVAC Concept

18

ASHRAE Research Project RP-1064:UFAD Design Guide

Project start: September 1999

Primary author – Fred Bauman

Contributing author – Allan Daly

Sponsored by ASHRAE and CBE

Technical oversight by TC 5.3, Room Air Distribution

Guide published by ASHRAE in December 2003

Available from ASHRAE bookstore

Developed ASHRAE Professional Development Seminar (PDS)

Fred Bauman, CBE 4


19

ASHRAE UFAD Design Guide

CONTENTS (243 pp.)1. Introduction2. Room Air Distribution3. Thermal Comfort and

Indoor Air Quality4. Underfloor Air Supply

Plenums5. UFAD Equipment6. Controls, Operation, and

Maintenance7. Energy Use8. Design, Construction, and

Commissioning

9. Perimeter and Special Systems

10. Cost Considerations11. Standards, Codes, and

Ratings12. Design Methodology13. Examples14. Future Directions15. Glossary16. References and

Annotated Bibliography17. Index

20

Development of UFAD Design Guide

Design Guide materialResearch (laboratory, field, simulation)

Design experience (literature, interviews, case studies)

Manufacturer’s literature

Includes UFAD and closely related task/ambient conditioning (TAC) systems

Covers topics in which important differences exist between UFAD and conventional overhead design

Identifies areas where more work is needed

21

Current status of UFAD technology

Strong interest due to several attractive featuresCurrent database of UFAD projects in North America

~300-400 installations

~50-55 million ft2

Routinely considered as HVAC design option

Ongoing research and experience in the field are generating new and improved information

Problems found in completed UFAD installations are often the same as those found in overhead buildings

Conservative design

Poor construction practice

Inadequate commissioning, controls, and operation

22

How Many UFAD Projects are Installed?

Through 2000, approximately 80 projects representing some 20 million sq ft in US.

Between 2000-2002, the number of new projects represented another 25 million sq ft.

CBE currently maintains database of North American UFAD projects with over 300 installations representing 50-55 million sq ft.

The jobs are getting larger. The Bank One Center in Chicago (1.5 million sq ft) was completed in 2003 and several more projects over 1 million sq ft are now in design or under construction.

23

UFAD market penetration

Alternative systems such as UFAD now being considered routinely as design options

Over 300 projects in CBE database, estimate ~400 in North America

North America – UFAD projects (estimated % of new commercial office buildings)

45%12%200515%7%200210%3%1999

Ratio

UFAD/Raised floor% Raised floor

24

UFAD Market Drivers

Lower churn costs (increase flexibility), allowing office space to be reconfigured faster and cheaper

Reduced energy use

Green building movement associated with the U.S. Green Building Council (USGBC) and LEED (Leadership in Energy and Environmental Design) rating system

Increased awareness of occupant benefits provided by personal comfort control and improved indoor air quality

Fred Bauman, CBE 5


Diffusers and Stratification

8:45 – 9:45

26

Diffuser types

Swirl

Variable area (VA)

Swirl, horizontal discharge

Linear bar grille

27

Swirl floor diffuser

Swirl Diffusers

28

Personal control of swirl diffuserRotate face plate

29

Personal control of swirl diffuser

30

Individual Plenum Box

Fred Bauman, CBE 6


31

Office cubicles

One diffuser per workstation32

Too many!

33 34

Variable-AreaDiffuser

ProprietaryProduct

35

Variable Air Volume Performance

Maintain constant discharge velocity even as air reduces

CONSISTANT VELOCITY - VARIABLE VOLUME

36

New VAV Diffuser with Time Modulation

Fred Bauman, CBE 7


37

Digital Pulse Width Modulation

38

Bar Grilles in Perimeter

39

New Linear Grilles for Perimeter

40

Perimeter solution:Underfloor variable-speed fan-coil

Raised Access Floor

Return Air Plenum

Return Air Grille

Linear Bar Diffuser

Flex Duct

Fan Coil w/ ECM motor

Glazing

T

Heating Coil

No U/A diffusers in perimeter zones

41

Heating Loop Output

130°F

60°F

Discharge AirTemperatureSetpoint

Fan

Spee

d

Max Fan Speed

Design Fan Speed

30% Design Fan Speed

Lowest PossibleFan Speed(~15% Max

Fan Speed)

Deadband Cooling Loop Output

Airf

low

Design Airflow

30% Design Airflow

Minimum Airflow(due to pressurized plenum)

Airflow

Fan Speed

Variable Speed Fan-Coil Control

42

Fred Bauman, CBE 8


43

Perimeter solution:Underfloor variable-speed fan-coil

44

Perimeter solution – variable-area diffuserCooling mode

45

Perimeter solution – variable-area diffuserHeating mode

46

Task/Ambient Conditioning Systems

Desktop control for maximum occupant comfort control

Relatively rare in practice

47

Diffuser Code Compliance

In the past, technically only all-metal diffusers could meet all code flame spread and smoke ratings

For plastic diffusers:UL 94 (Flammability of Plastic Devices)

NFPA 90A (smoke developed index <= 50)

Smoke test protocol is NFPA 255 (burn 25 ft sample)

NFPA 90A exception (smoke optical density)

NFPA 262 or UL 2043 (new test for smoke generation from plastic diffusers in 2002 edition of NFPA 90A)

48

Room air stratification(cooling operation)

Fred Bauman, CBE 9


49

Overhead Air Distribution System

Mixing system tries to maintain uniform temperature and ventilation conditions throughout space

50

Displacement Ventilation System

Minimize mixing in occupied zone Stratification height (SH) separates upper and lower zones

51

Displacement Ventilation Diffusers

Schools, atriums

Auditoriums, theaters

52

Displacement Ventilation Installations

School Atrium

53

Underfloor Air Distribution System

Increased mixing up to throw height (TH)Diffuser throw below stratification height (SH)

54


Diffuser throw above stratification level (SH)

Fred Bauman, CBE 10


55

Air Patterns

displacement

swirl

56

Diffuser Comparison

ModelDischarge

Setting Airflow

Vertical Throw to

50 fpmClear Zone

Radius[ft3/min] [ft] [ft]

Vertical 100 4 - 6 1.5Vertical 75 2.5 - 4.5 1.5

Variable Vertical 150 8 2.0Area Full Spread 110 5 4.5

Vertical 75 / ft 25 -Vertical 40 / ft 18 -

Swirl

Bar

57

Room Air Stratification Testing

ApproachFull-scale laboratory tests of commercially available floor diffusers in realistic office setting.Study impact of various design and operating parameters on room air stratification (RAS).

SignificanceControl of stratification is crucial to:

Proper designSystem sizingEnergy efficient operationThermal comfortIndoor air quality

58

Room Air Temperature Profile

CeilingHeight

Temperature

Head (67 in.)

Ankle (4 in.)

Tstat (48 in.)Toz,avg

Occupied zone (OZ)

∆Troom

∆TozSAT

Tstat

RAT

Temperature near the floor

Temperature at head height

59

Stratification test results Effect of airflow rate: constant load, swirl diffusers, interior zone, SAT=65°F

0

1

2

3

4

5

6

7

8

9

10

11

69 70 71 72 73 74 75 76 77 78 79 80 81 82

Room Temperature, °F

Hei

ght,

ft

1.0 cfm/sq. ft0.6 cfm/sq. ft0.3 cfm/sq. ft

5°F ∆TASHRAE Std.55-2004

Still satisfies vertical temperature difference (5°F) with 40% less air

60

Stratification Test Results Effect of throw height: Swirl diffusers, constant load/room airflow

0

1

2

3

4

5

6

7

8

9

10

68 70 72 74 76 78 80

Room Temperature [°F]

Hei

ght [

ft]

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.020.0 21.1 22.2 23.3 24.4 25.6 26.7

Room Temperature [°C]

Hei

ght [

m]

6 diffusers, highest throw

8 diffusers

10 diffusers

12 diffusers

14 diffusers, lowest throw

6 workstations

Interior zone with constant diffuser supply air temperature = 65°F

Fred Bauman, CBE 11


61

Variable Area vs. Swirl

0

1

2

3

4

5

6

7

8

9

10

11

69 70 71 72 73 74 75 76 77 78 79 80 81 82

Room Temperature, °F

Hei

ght,

ft

SW-1SW-2VA-1VA-2VA-3

VA Diffuser

Swirl Diffuser

T e s t

R o o m L o a d W /ft 2

R o o m A ir f lo w c fm /f t 2

D if fu s e r f lo w ra te ,

(% o f d e s ig n )

5 0 f p m T h ro w

f t V A -1 2 .6 0 .8 7 0 % 7 V A -2 2 .9 0 .8 3 0 % ~ 7 V A -3 1 .8 0 .4 4 0 % ~ 7 S W -1 2 .5 0 .6 9 0 % ~ 4 S W -2 2 .7 0 .6 4 0 % ~ 2

Source: ASHRAE Journal May 2002

62

Stratification Test Results Effect of supply air temperature: constant load/airflow, swirl diffusers

63

Stratification and Airflow in Perimeter ZonesEffect of blinds and throw height: bar grilles, constant load

0

1

2

3

4

5

6

7

8

9

10

68 70 72 74 76 78 80 82 84

Room Temperature [°F]

Hei

ght [

ft]

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.020.0 21.1 22.2 23.3 24.4 25.6 26.7 27.8 28.9

Room Temperature [°C]

Hei

ght [

m]

Blinds open, 8 Linear bar grilles, vanes at 90°1.6 cfm/sf

Blinds open,10 Linear bar grilles, vanes at 53°1.3 cfm/sf

Blinds closed,8 Linear bar grilles, vanes at 90°1.0 cfm/sf

Peak solar load

Constant diffuser supply air temperature = 65°F64

RAS Testing Results(Cooling performance)

The amount of stratification is primarily driven by room airflow relative to load, and throw height.

Stratification will increase as room airflow and/or diffuser throw height are reduced for constant heat input.

If too much air is delivered or throw height is too high, stratification will be reduced (approaching a well-mixed system), thereby compromising energy performance (increased fan energy, and lower RAT).

Optimized control strategies should promote stratification (reduce airflow requirements), while balancing this with comfort considerations (∆T < 3-4°F in occupied zone).

To offset the effects of stratification, consider increasing thermostat setpoint by 1-2°F, especially in interior zones.

65

RAS Testing Results (Perimeter zone cooling)

Key perimeter zone issuesSupply air temperature

Diffuser throw height, airflow rate, amount of mixing

Blinds up or blinds down

Airflow rates significantly lower with blinds closed and lower throw

66

Perimeter Office1st floor, east perim

66

68

70

72

74

76

78

80

Tue

8/22

Wed

8/2

3

10'8'6'4'2'0'

Monitored Data from an Underfloor System

stratificationduring cooling

mode

mixingduringheatingmode

SensorLocations

noon6am 6pm

Stratification (in practice)

Fred Bauman, CBE 12


67

Controlling Room Air Stratification

GuidelinesPromote stratification (reduce airflow requirements), while maintaining comfort: ∆T < 3-4°F in occupied zone.

Don’t be too conservative! Airflow should be about the same as OH systems.

Provide controls to reduce airflow to interior (rather than raise setpoint only) in case sizing is too conservative.

Technology needsCooling airflow design tool

Impact of stratification on thermal comfort

Identify thermostat control strategies

Comfort and IAQ

9:45 – 10:15

69

Thermal ComfortVariations in Individual Preferences

Clothing

Activity level

Body weight & size

Personal preferences

70

Thermal Comfort

Light office activity, light jacket, slacks

Sedentary, Skirt, blouse, pantyhose

71

Personal Control

Field research: Occupants with no control are twice as sensitiveto temperature changes

Less control = more hot/cold complaints

72

Thermal Comfort

Traditional approachSatisfy up to 80% of building occupants

Underfloor approachAllow personal control of the local thermal environment satisfy up to 100% of occupants reduce occupant complaints

Existing fan-driven (TAC) supply outlets provide sizable range of temperature control:desktop 13°F (7°C); floor 9°F (5°C)

Passive diffusers (no fan power) don’t provide as much local temperature control, but improve perception of individual control

Fred Bauman, CBE 13


73

Comfort Standards(Impact of stratification on thermal comfort)

ASHRAE 55 and ISO 7730 define a 5°F (3ºC) limit on vertical air stratification The limit was based on Olesen’s study in 1979 on 16 college students

74

Ongoing Comfort Research

Use the CBE advanced thermal comfort model to evaluate comfort in stratified environments

Transient, thermo-physiological model16 body segmentsHeat loss by evaporation (sweat), convection, radiation, and conductionDetailed clothing modelUser-defined 3-D geometry and detailed boundary conditions, including local temperatures and velocities, direct solar load, and radiation heat transfer from room surfaces

CBE comfort model

75

Thermal comfort in stratified environments

Paper presented at Indoor Air 2005, Beijing, China

clo=0.6, met=1.0

ASHRAE/ISO Stratification Limit

0

1

2

3

4

5

6

7

8

23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5

Operative temperature (ºC)

Acc

epta

ble

Stra

tific

atio

n (º

C)

73.4 74.4 75.4 76.4 77.4 78.4 79.4 80.4 81.4

Operative temperature (ºF)

76

Ongoing Comfort Research

CBE advanced thermal comfort model indicates that greater stratification (> 5°F) may be acceptable in middle of comfort zone.

New research is needed to define comfort criteria in stratified environments

Impact of stratification over full range of comfort zone temperatures

Comfort with and without personal control

Impact of localized heating or cooling (TAC systems) on thermal comfort

77

Indoor Air Quality

Traditional approachProvide uniform ventilation throughout space

Underfloor approachFresh air is delivered closer to the occupants

Floor-to-ceiling air flow pattern provides improved IAQ in occupied zone (up to 6 ft [1.8 m])

Local air supply improves air motion, preventing sensation of stagnant air (associated w/ poor IAQ)

78

Room Air Stratification(cooling operation)

Fred Bauman, CBE 14


79

Air Change Effectiveness (ACE)

)(τlevelbreathingatairofAge)(τreturnatairofAge return

bl

levelbreathingatACELocal =

ACE < 1 short circuiting

ACE = 1 mixed

ACE > 1 better ventilation performance

τreturnτbl

80

ASHRAE Std. 62.1-2004, Addendum N

Global air change effectiveness (ACE)Overhead (OH) systems(0.8 heating, 1.0 cooling)

Displacement ventilation (DV) (0.7 heating, 1.2 cooling)

Underfloor air distribution(no data available yet: 0.7 heating, 1.0 cooling)

Task/ambient conditioning(up to 2.7 for desktop supply)

Local air motion improves perceived air quality

81

German Study of Ventilation Performance

“Analysis and Testing of Methods to Determine Indoor Air Quality and Air-Exchange Effectiveness”Authors: Andreas Jung and Prof. Manfred ZellerRheinisch-Westfälische Technical University of Aachen, GermanyPublished 1994Sponsored by FLT – Research Federation for Air and Drying TechnologyLaboratory studyCBE has translated the report to English and will post on CBE website

82

Test conditions

100% outside air for all tests

Four diffuser typesCeiling twistCeiling slotFloor twist (UFAD)Displacement ventilation (DV)

CASE 1Investigate impact of air exchange rates (2.5, 5 and 8 per hour = 0.35, 0.7 and 1 cfm/sf) at constant internal load (20 W/m2 = 1.8 W/ft²)

CASE 2Investigate impact of arrangement and type of heat sources (3 load levels: 20, 40 and 65 W/m2 = 1.8, 3.7 and 6 W/ft2)

Air exchange rates were adjusted to maintain same room temperature difference (return – supply) of about 8.5K = 15.3°F

83

Floor twist diffusers

Test ConditionsNumber and arrangement of diffusers changed between tests to achieve constant airflow rates per diffuser (~35 m3/h = 20 cfm)

Throw height of diffusers is ~1.1 m (3.6 ft)

Due to small airflow per diffuser, there were a large number of diffusers distributed across floor

84

Floor and ceiling plans

6m = 19.7ft

4m = 13.1ft

24m²

258ft²

DV diffusers

Swirl diffusers

Ventilated light fixtures for return air

Ceiling twist

diffuser

Ceiling slot diffusers

Fred Bauman, CBE 15


85

Location of heat sources

Nearly adiabatic conditions

1

2

3

86

Local values of ACE for design case

87

Findings for floor twist diffusers – Case 2Local and global air exchange effectiveness

At section 2 of test chamber

Global ACEs

88

Conclusions – German Study

Ceiling twist and ceiling slot diffusers Create nearly mixed conditions

Attention to short-circuiting

Floor twist diffusers and DV systemsSignificantly increase supply of fresh air within the breathing zone of occupants

UFADGlobal ACEs are in the range of 1.2 to 1.3

Local ACEs are in the range of 1.2 to 1.8

DVGlobal ACEs are in the range of 1.2 to 1.3

Local ACEs are in the range of 0.8 to 3.7

Research needed to investigate typical U.S. UFAD configurations

89

Research needed

Ventilation performance in UFAD systemsLack of quantitative data on ventilation performance of current-generation UFAD systems

ASHRAE 1373-TRP: Air distribution effectiveness with stratified air distribution systems.At the ASHRAE Annual Meeting in Quebec City (June 2006) proposals were reviewed by TC 5.3 for a laboratory and CFD study of UFAD and displacement ventilation systems. A contractor was selected and work should begin soon (2-year study)

CBE is seeking funding to conduct field study (with Lawrence Berkeley Laboratory) of ventilation effectiveness and pollutant removal efficiency in existing UFAD office building

Break

10:15 – 10:30

Fred Bauman, CBE 16


Underfloor Plenums

10:30 – 11:25

92

Underfloor Air Supply Plenums

Room

Return Plenum

93

Plenum Design Variations

Pressurized plenumPassive diffusers

Most common approach and focus of current practice

Zero-pressure plenumActive (fan-powered) diffusers

Not as popular due to perceived higher costs

Fully ductedNot as popular due to high cost and lack of flexibility

Most designs are hybrid solutions

94

Airflow Performance Issues

Objective – deliver desired amount of airPressurized vs. zero-pressure

Reduced static pressure

Plenum height (obstructions)

Size of plenum zone

Air leakage

Plenum inlet conditions

Inlet velocity

Inlet direction (open, vanes, plates)

Location in zone

Number of inlets in zone

95

Underfloor Air Supply PlenumsResearch Results

Phase 1 – Airflow PerformanceObjective Investigate practical plenum configuration issues, including minimum plenum height, for which acceptable airflow performance can be achieved in pressurized underfloor plenums.

ApproachEmpirical experiments in full-scale underfloor air supply plenum test facility.

96

Full-Scale Plenum Test Facility

40'

80'

M M M

MM M M

M M

M

Flowmeasuring

station

Fan

23"x 23"Duct

Plenum inlet

Measurementpoint (typical)

Removablefloor panels (2)Obstruction #1

Obstruction #2

4' Underfloorbarrier

4" x 14" Floor grills(typical)

5' 10' 10' 10' 10' 10' 10' 10' 5'

Raised Floor

Concrete Slab

24'19'

14'10'

Section View

Plan View

Fred Bauman, CBE 17


97

Plenum Schematic Cross-Section

1-inch Floor Panel

Concrete Slab

1"

2"

2"

2"

2" Po

lysty

ren

e B

locks

2"3"

7"

Finish Floor Level

Plenum Schematic Cross-Section

98

Results

Airflow delivery is very uniform from an 8-inch pressurized underfloor plenum over a full range of supply volumes (0.5-1.5 cfm/ft2), even at a distance of 80 feet from the plenum inlet.

Uniformity (less than 10% variation) is preserved for solid obstructions with only 1.5 inches of clear space.

99

Air Flow Ratio: 8-inch plenum

70%

80%

90%

100%

110%

120%

130%

0 10 20 30 40 50 60 70 80

Distance from Fan Inlet (ft)

Del

iver

ed A

ir Fl

ow R

atio

(M

easu

red

flow

/Uni

form

flow

)

1.5 cfm/sf

1.0 cfm/sf

0.5 cfm/sf

100

Publication

“How Low Can You Go?”Air Flow Performance of

Low-Height Underfloor Plenums

F. Bauman, P. Pecora, and T. Webster Center for the Built Environment

University of California Berkeley, California

October 1999

PDF available from: www.cbe.berkeley.edu/underfloorair

101

Plenum air leakage

Category 1 – Construction quality leakage

102

Plenum air leakage

Category 2 – Floor leakage

Fred Bauman, CBE 18


103

Smoke TestAir leakage between Floor Panels

104

Air Leakage Test Setup

105

Carpet Tile Configurations

Aligned Offset

106

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Pressure (in. w.c.)

Air

Leak

age

(cfm

/ft2 )

Bare panelsAligned carpetOffset carpet

Air Leakage between Floor PanelsCarpet Tile Configurations

107

Thermal Performance IssuesPressurized Plenums

Objective – deliver air at the desired temperature using a minimum amount of energy

Plenum inlet conditionsSupply air temperature

Inlet velocity and direction

Thermal decayHeat transfer coefficients (slab and panels)

Velocity and residence time of air in plenum

Temperature profile in slab and floor panels

Temperature on underside of slab

Thermal storage strategies (nighttime pre-cooling)

108

Temperature variations in underfloor plenum

Temperature [F]

Fred Bauman, CBE 19


109

Ongoing Research on Underfloor Plenums

Phase 2 – Thermal Performance

CFD model of underfloor plenum

Full-scale experiments

Validate model vs. test facility

Study thermal performance (supply temperature variations and thermal storage control strategies)

110

Effect of Plenum Inlet Conditions

a)

Inlet

Diffusers

Diffusersb)

Inlet

Vanes

Plan view of plenum air flow patterns: (a) without inlet vanes, (b) with inlet vanes

111

Plenum Air Temperature – CFD Model

Focused jet

(°F)

112

CFD model: Particle visualization

Temperature (°F)

113

Full-Scale Plenum Test Facility

114

Smoke Visualization

Fred Bauman, CBE 20


115

Underfloor plenum guidelines

Airflow delivery and pressure distributionQuite uniform across open pressurized plenum zone

LeakageAccount for leakage into occupied space in design airflow calculations

Careful attention to construction quality and sealing of plenum

Recommend leak test at end of construction (guidelines needed)

Thermal decay 50-65 ft (15-20 m) maximum to furthest diffuser

Plenum inlet conditions can be important116

Plenum guidelines: Thermal decayGuidelines to reduce temperature gain

Avoid excessive inlet velocities (< 1,500 fpm)

Spread out airflow pattern

Consider perimeter inlet locations (shafts), if possible

Consider use of CFD simulations

In larger zones, use some ductwork in critical areas

117

500 FPM 800 FPM 1000 FPM 1200 FPM 1500 FPM

0.00.20.40.60.81.01.21.41.61.82.0

50 75 100 125 150

Length (ft)

Tem

pera

ture

Ris

e (°

F)

50 75 100 125 150

Length (ft)

Plenum guidelines: Temperature rise in air highways

No slab insulation With R-10 slab insulation

Horizontal and VerticalDistribution

11:25 – 11:40

119

Plenum Distribution Criteria

General, uniform air distribution

Relatively equal supply air temperature to each diffuser

Relatively equal pressure in plenum

120

Horizontal Distribution

Layout Example:

Initial Plan –Large amount of

ductwork

Fred Bauman, CBE 21


121 122

Shafts

Horizontal Distribution

Layout Example:

Final plan employs multiple shafts to reduce ductwork in the

floor

123

50 foot radius

124

“Air Highways”

125

“Air Highway” Cross Section

126

Large Air Highway

Fred Bauman, CBE 22


127

Air Highway Construction

128

Air Highway Goals

Lower costsLess sheet metal

Lower labor rates of floor installers

Lower pressure dropLarger effective duct area

Reduced coordination and conflicts

Leak-free

129

Air Highway Limitations

Questionable actual cost savings

Familiarity of construction by floor contractors, general contractor

Code equivalence to a ductCrossing corridors

Construction coordinationNot complete until floor tiles installedDamage by other trades

Limited pressure capability

Leakage!!!!

130

The need for

Plenum Dividers

Sheet metal plenum dividers subdivide UF plenum

Purpose:Provide more interior control zones

Reduce length of air travel to perimeter UFTsReduced temperature degradation

Allow off-hour isolationMeet Title 24 25000 ft2 isolation area limitation

131

Plenum Dividers

Plenum DividersMaximum 25000 ft2 area per zone

132

Recommendations

Use as little underfloor ductwork as possibleMinimize cost

Minimize conflicts

50 feet from discharge to last outlet seems to be the consensus (more research being done)

Use many vertical shafts to try to eliminate horizontal ductwork

Cost of fire/smoke dampers offset by eliminated ductwork

Reduced velocity leaving shaft, reduces noise

Fred Bauman, CBE 23


Demo of McCoy UFAD Showroom

11:40 - 12:00

Lunch

12:00 - 1:00

Load Calculations,Energy

1:00 - 1:45

136

Does UFAD Require More Air?

Underfloor:Supply Temp: 63 F

Room Setpoint: 75 F

Space Heat Load: 17,297 Btu/hr

CFM = 17,291 Btu/hr = 1,335 CFM

1.1 Btu/hr-cfm-F x (75F-63F)

Overhead:Supply Temp: 55 F

Room Setpoint: 75 F


CFM = 17,297 Btu/hr = 786 CFM

1.1 Btu/hr-cfm-F x (75F-55F)

Assuming complete mixing:

Answer: No! The assumption of complete mixing is incorrect!

137

Overhead Air Distribution System

Mixing system tries to maintain uniform temperature and ventilation conditions throughout space

138


Increased mixing up to throw height (TH)Diffuser throw below stratification height (SH)

Fred Bauman, CBE 24


139

Heat Transfer in UFAD Systems

140

Energy Flows in Stratified UFAD System

BackgroundIn a conventional building using an overhead well-mixed system, 100% of the space heat gains are removed by warm return air leaving the room at ceiling level (heat extraction).

QuestionHow is heat removed from a stratified room in a multi-story building with UFAD?

ApproachAssumption of perfect mixing is no longer validSimplified first-law (energy balance) model

Publication“Heat Transfer Pathways in UFAD Systems”F. Bauman, H. Jin, and T. WebsterASHRAE Transactions, Vol. 112, Part 2, 2006.

141

Cooling Operation of Overhead System

Heat gain into space

100%

Extraction 100%

142

Supply Supply PlenumPlenum

Ceiling-floor radiation

Floor-room convection

Return PlenumReturn Plenum

Return Return PlenumPlenum

Slab

Slab

Treturn

Treturn

Treturn

Tceiling

Tcarpet

Tplenum

Troom, near floor = 72°F

Slab-supply plenum conduction/convection

Slab-supply plenum conduction/convection

Floor-supply plenum conduction/convection

Return-ceiling convection

Return-slab convection

RoomRoom

Raised Floor Raised Floor PanelsPanels

Ceiling-slab radiation

0.6 cfm/ft2

78°F

Simplified Model – Heat Transfer Pathways

Diffuser discharge = 65°F

143

Predicted Distribution of Room Cooling Load

Total into plenum 43%


100%

Return air extraction

57%

Through floor 14%

Through slab 29%

Assumptions: Room cooling load = 4.3 W/ft2, Airflow = 0.6 cfm/ft2, SAT = 65°F

72°F

78°F

65°F

144

Distribution of Room Cooling LoadImpact of room airflow rate

0

10

20

30

40

50

60

70

80

90

100

0.6 0.8 1.0

% o

f Tot

al R

oom

Coo

ling

Load

0

5

10

15

20

25

30

35

40

45

W/m

2

Heat Transfer Through Floor into PlenumHeat Transfer Through Slab into PlenumReturn Air Extraction Rate

0.6 cfm/ft2 0.8 cfm/ft2 1.0 cfm/ft20

10

20

30

40

50

60

70

80

90

100

0.6 0.8 1.0

% o

f Tot

al R

oom

Coo

ling

Load

0

5

10

15

20

25

30

35

40

45

W/m

2

Heat Transfer Through Floor into PlenumHeat Transfer Through Slab into PlenumReturn Air Extraction Rate

0.6 cfm/ft2 0.8 cfm/ft2 1.0 cfm/ft2

Fred Bauman, CBE 25


145

EnergyPlus Modeling

Considering Radiation is KEY to making sense out of heat flows in UFAD systems (and all systems).

Internal Loads Example(3.6 W/ft2)

Tsupply = 56Tplenum = 63Troom = 75Treturn = 76

System ΔT = 76-56 = 20Room ΔT = 75-63 = 13

18.8

17.8

16.2

17.4

22.5

24.223.9

29.1

24.4

24.3

24.3

23.8

23.8

17.4

13.4

23.6

0

20

40

60

80

100

120

140

160

180

10 15 20 25 30

56

63

75

76

ΔTroom=13

ΔTsystem=20

75

146

Conclusions – Heat transfer pathways

Heat transfer into underfloor plenums represents a significant percentage (at least 1/3) of the room cooling load

Increased airflow will decrease both the plenum temperature gain and room air stratification, although at the expense of higher fan energy

Depending on climate, different plenum operating strategies may be considered (EnergyPlus)

Mild, no humidity control – increase airflow to allow higher plenum inlet temperature (maximize economizer)

Humid – reduce airflow to maximize fan energy savings, since no economizer potential

147

Load Calculation/Energy Software Tools

Common load/energy calculation programsTrane Trace 700/Load 700

Carrier HAP

Elite

Wrightsoft RSC

DOE2.1, 2.2

No Underfloor Model in any of them!For load calculations, air volumes seem to work out to be the same as overhead calculations (so far…)

New version of EnergyPlus/UFAD scheduled for release in summer 2006

148

Load Calc’s: What to do?!?

Designers need to understand the physics of these systems

Cooling airflow design tool under development

Must design systems that can react to dynamic load conditions

VAV system operation important

Resets seem to be very helpful

Systems must be commissioned to make sure they work

149

Cooling airflow design calculations

Where:Q = total heat gains to room (Btu/hr)

CFM = total room airflow (ft3/min)

ΔT = temperature difference between the room setpoint temperature and the supply air temperature (°F)

TCFMFcfmhr

BtuQ Δ××°⋅⋅

= )1.1(

Overhead System

Assumes complete mixing

150

OverheadSupply Temp: 55°F

Room Setpoint: 75°F


= 786 CFM

Sample airflow calculation (w/ complete mixing)

)5575()/(1.1/297,17

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

TFcfmhrBtuQCFM

Δ×°⋅⋅×=

)/(1.1

Assumption of complete mixing is incorrect!

UFADSupply Temp: 65°F



= 1,572 CFM (double)

)6575()/(1.1/297,17

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

Fred Bauman, CBE 26


151

Room air stratification

152

Overhead Supply Temp: 55°F



= 786 CFM

Sample airflow calculation (w/ stratification)

)5575()/(1.1/297,17

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

TFcfmhrBtuQCFM

Δ×°⋅⋅×=

)/(1.1

Assumption of stratification alone is not enough!




= 1,123 CFM (43% higher)

)6579()/(1.1/297,17

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

153

Heat transfer into underfloor plenum

Total into plenum = 30-40%, depending on airflow rate


100%

Return air extraction

60-70%

Through floor 10-15%

Through slab 20-25%

Assumptions: Room cooling load = 4.3 W/ft2, Airflow = 0.6-1.0 cfm/ft2, SAT = 65°F

65°F

Predicted distribution of room cooling load

154

Overhead (OH)Supply Temp: 55°F



= 786 CFM

Sample airflow calculation (w/ plenum heat gain)

)5575()/(1.1/297,17

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

TFcfmhrBtuQCFM

Δ×°⋅⋅×=

)/(1.1

Estimated airflow is the same for OH and UFAD!



Space Heat Load: 0.7(17,297 Btu/hr)

= 12,108 Btu/hr

= 786 CFM

)6579()/(1.1/108,12

FFFcfmhrBtuhrBtuCFM

°−°×°⋅⋅×=

155

Simple design tool concept

Modify existing “well-mixed” tool

Qmod is the total room cooling load reduced by the heat gain to the underfloor plenum.

ΔTmod is equal to Treturn – Tsupply, accounting for stratification. User could specify target ΔT in the occupied zone.

Design tool could also estimate average temperature gain in the underfloor plenum, and therefore the required plenum inlet temperature.

mod

mod

)/(1.1 TFcfmhrBtuQCFM

Δ×°⋅⋅×=

156

UFAD: Good Energy Performance

Cooling EnergyFree CoolingMechanical Cooling

Fan EnergyAir PressuresAir Volumes

Reheat EnergyLower ΔTLower Air-Volumes

Fred Bauman, CBE 27


157

Energy Advantages in the San Francisco Area

San Francisco Outdoor Temperature Distribution(Dry Bulb temperatures between 8am and 8pm)

0

50

100

150

200

250

300

33 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95

Outdoor Dry Bulb Temperature [F]

Hou

rs

2217 Hours100% Economizer

158

UFAD in Other Climates

0

100

200

300

400

500

600

-25

-20

-15

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10

0

0

100

200

300

400

500

600

-25

-20

-15

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10

0

0

100

200

300

400

500

600

-25

-20

-15

-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 10

0HV

AC

De

sig

n F

und

am

enta

ls

San Francisco

Minneapolis

Houston

159

Dehumidification

Chilled water supply temperature is determined by the lowest supply-air temperature needed.

If dehumidification is needed, this is likely to be 55oF or lower.

Affects both mechanical and free cooling.

55oF

55oF

40oF52oF

160

Return air bypass for humidity control

outside air intake

exhaust outlet

returnair

supplyair

21

09 14

bypassairreturn

air

exhaust fan

vfd

vfd

08 11

H

07

P

12 15 16

P

T 17

P

T

T

22 24

P

T

23

T

10

H

18

25

mixed airplenum

plenum fan

return airplenum

19 20

26

H

T

13

P

27

N.C.

N.O. N.O.

cooling coil

161

Mechanical Cooling Energy Savings

Chiller energy decreases as the chilled water supply temperature increases – the compressor does less work 65oF

65oF

50oF62oF

162

Mixing OH and UFAD Systems

Chilled water supply temperature is determined by the lowest supply-air temperature needed

If standard OH systems are used, this is likely to be 55oF.

Affects both mechanical and free cooling.

65oF

55oF

40oF52oF

Fred Bauman, CBE 28


163

Reheat Energy

ExamplesItem Units Symbol / Equation OH UFAD

Heating Load [Btu/h] Qh 10,000 10,000System Supply Air Temp [F] Tsys 55 63Room Heating Setpoint [F] Tset 70 70Room Supply Air Temp [F] Tsupply 90 110

Supply Air Flow [CFM] Qh / (1.1 x (Tsupply-Tset)) 455 227Reheat [Btu/h] CFM x 1.1 x (Tset - Tsys) 7,500 1,750

23%

164

Structural Slab Thermal Storage

Building physics and anecdotal evidence suggest there is a strong coupling of plenum air and slab.

No validated mathematical models exist that can be used in design.

CBE, CEC, UCSD, and DOE working on it (EIEIO).

165

Reduced Fan Power

Underfloor plenum is the primary air distribution route

UFAD systems use less ductwork than OH systems

Primary fan pressure reduced 1/2 to 1 in. H2O, a reduction of about 25%

Substantial energy savings on primary fan power possible, however this may be offset by fan-powered boxes or terminals used in perimeter zones

166

Fan Energy Savings: Air Volumes

Calculations and practice suggest that UFAD systems do not require more air than OH systems due to stratification

But…

There are many unknowns associated with load calc’s

It appears that built projects in case studies provide too much air

Further research will allow us to more accurately predict design airflow volumes

Commissioning and Operations1:45 – 2:15

168

Plenum air leakage

Category 1 – Construction quality leakage

Fred Bauman, CBE 29


169

Plenum air leakage

Category 2 – Floor leakage

170

Plenum Leakage in Construction

171


172


173

Sealing Around Column in Construction

174

Plenum Air LeakageConduct leakage tests in underfloor plenum

Maintain design plenum pressure (e.g., 0.05 in. H2O)1. Blower panel with variable-speed test fan, or2. Use central AHU, but must measure airflow entering plenum

Test #1 – Total leakageFloor panels, electrical outlets, carpet tiles installed according to typical design specifications

1. Seal all diffusers, or2. Estimate airflow through diffusers using manufacturer’s data

Test #2 – Construction quality leakage1. Seal all openings and gaps on raised floor surface, or

2. Estimate leakage using manufacturer’s data

Floor leakage1. Subtract Test #2 result from Test #1 result, or

2. Subtract Test #2 estimated airflow from Test #1 result

Fred Bauman, CBE 30


175

Acceptable Leakage Rates

Construction quality leakageNot to exceed 0.05 cfm/ft2 at 0.05 in H2O (e.g., 1,000 cfm for a 20,000 ft2 floor plate at 1 cfm/ft2)

Is this a reasonable target?

Floor leakageNot to exceed 0.10 cfm/ft2 at 0.05 in H2O(e.g., 17% leakage for an interior zone with 0.6 cfm/ft2

design airflow)

Consider testing a full-scale mock-up prior to construction. Apply corrections and sealing methods to remaining underfloor plenums and test again.

176

Airflow and Room Air Stratification

No cooling airflow design tool yet available

Systems are commonly oversized, often as a result of over-estimation of design loads

Conduct measurements of vertical temperature profile during fully loaded conditions

Use “stratification measurement tree” consisting of string or pole with several temperature sensors at regular intervals

Typical or simulated loads must be present to determine stratification performance

Prior to measurements, operate building long enough (up to one week) to ensure thermal mass of structural slab is in equilibrium

Preferred time for testing would be 3-6 months after occupancy

If stratification in the occupied zone (up to 6 ft) is not at least 3°F, further adjustments should be made

177

Adjusting -“Tuning Up”- Stratification(at peak load)

Parameters to adjustAirflow quantity

Plenum pressure max setpoint

# of diffusers

Tstat setpoint

Supply air temperature

Goal for adjusted stratification profile∆T ~ 3-4°F in occupied zone

Equivalent comfort (same average temperature in the occupied zone)

178

Adjusting Thermostat Setpoint

CeilingHeight

Temperature

Ankle (4 in.)

21

74°F

~ 72 - 73°F

Thermostat (48 in.)

Average for Setting 2

Setting 1Setting 2

Adjust set point to achieve desired occupied zone average temperature (may increase gradient also)

Average for Setting 1

179

Adjusting -”Tuning Up”- Stratification(at peak load)

CeilingHeight

Temperature

Head (67 in.)

Ankle (4 in.)

Tstat (48 in.)

1 2 3

Tstat3Tstat1

Toz1,avgToz2,avg

Occupied zone

= Tstat2= Toz3,avg

180

∆Toz ~ 1°F

Adjusting -”Tuning Up”- Stratification(at peak load)

CeilingHeight

Temperature

Head (67 in.)

Ankle (4 in.)

Tstat (48 in.)

1 3

Occupied zone

∆Toz ~ 3-4°F

Fred Bauman, CBE 31


181

Other Considerations

Close coordination between designers, contractors, commissioning agents, and building operators

Building operators must be properly trained on UFAD design and operation

Raise TStat setpoints to avoid overcooling (interior zones)

Avoid overriding higher airflows into open plenum – impacts the entire plenum zone

If plenum air temperature is too high, corrections may be needed

Account for temperature gain to plenum supply air, particularly in key areas

Perimeter zones

Conference rooms

BMS should allow easy retrieval and review of archived trend logs to evaluate system performance

Post-Occupancy Evaluations

2:15 – 2:30

183

CBE occupant satisfaction survey

CBE’s occupant satisfaction survey offers a systematic, cost-effectiveway of measuring how satisfied occupants are with their workplace environments.

184

Survey implementation

Survey notification via email

Occupants respond to web-based survey Data sent to

SQL server database

Results reported online

185

Satisfaction with indoor air qualityOccupant survey results

- 3 30

+0.88 mean satisfaction7 UFAD bldgs, 1,344 responses

+0.23 mean satisfaction152 overhead bldgs, 25,749 responses

Reference: www.cbesurvey.org

How satisfied are you with the air quality in your workspace (i.e. stuffy/stale air, cleanliness, odors)?

186

Satisfaction with thermal comfortOccupant survey results

- 3 30


-0.21 mean satisfaction152 overhead bldgs, 25,749 responses


How satisfied are you with the temperature in your workspace?

Fred Bauman, CBE 32


187

Satisfaction with lightingOccupant survey results

- 3 30




How satisfied are you with the amount of light in your workspace?

188

Satisfaction with acoustic qualityOccupant survey results

- 3 30

-0.16 mean satisfaction7 UFAD bldgs, 1,344 responses



How satisfied are you with the noise level in your workspace?

189

Satisfaction with cleanlinessOccupant survey results

- 3 30




How satisfied are you with the general cleanliness of the overall building?

190

CBE UFAD project databasewww.cbe.berkeley.edu/underfloorair/casestudies.htm

~300 projects in North AmericaWeb-based questionnaire collecting key building characteristics ~32 buildings under active study; 13 have completed operations section of questionnaire

191

UFAD building operations questionnaireCompleted by facility managers

Based on your knowledge of how the UFAD system has been operating and your experience in other non-UFAD buildings, how much better or worse is this building in comparison to conventional buildings with respect to:

Much better Much worse3 -30

Operations issue NMean

response

0.1513Effort and cost of maintenance

0.5413Hot and cold complaints

0.6213Overall performance of UFAD system

0.6713Energy use

0.9213Making changes to tenant space

192

UFAD building operations questionnaireCompleted by facility managers

Based on your experience with this building, indicate how serious of a problem the following have been:

No problem Serious problem3 -30

Operations issue NMean

response

-0.1713Air leakage from construction joints

0.1713Plenum airflow and thermal decay

0.9213Air leakage from panel joints

1.2513Dust and dirt in plenum

1.6713Temp. stratification in occupied spaces

2.0813Moisture, mold, related problems

Fred Bauman, CBE 33


How to Decide toGo with UFAD?

2:30 – 2:45

194

Cost considerations – UFAD vs. overhead

Accurate first and life-cycle cost estimates are crucial early in design process

Added first cost of raised floor system can be offset (in part) by reduction in ductwork and electrical/telecomm installation costs

Recent projects have demonstrated that first costs for UFAD can be very comparable to overhead systems

Range from $1.00-1.50/ft2 reduction to $4.00-6.00/ft2 premium

Well-recognized that raised floor systems reduce life-cycle costs associated with churn

As more designers become familiar with UFAD and more manufacturers enter the market, costs will come down further

195

Relative costs

$-

$50

$100

$150

$200

$250

Cost of Labor Cost of Energy Incremental Cost of UFAD

Offi

ce B

uild

ing

Cos

t per

Squ

are

Foot

A 1% Savings in Productivity

~1 year payback

196

Ongoing CBE UFAD Cost Analysis Project

Objective: Develop comprehensive first and life-cycle cost model for UFAD systems

Funded by U.S. GSA

Began summer 2002, ~$450K budget

Project statusFirst cost model complete

Development of life-cycle cost model underway

UFAD cost model and total cost analysis complete by Fall 2006

197

Approach - Affected first cost elements

The model evaluates each affected element and computes the UFAD to overhead (OH) system cost difference

Access Floor: Installation of access floors & carpets

Façade & structure: Allowance for reducing floor-to-floor height

HVAC: Cooling and heating loads calculation for sizing and pricing tenant area HVAC costs

Electrical: Power distribution and voice and data differences

Raised Core: Raised slab in core (non-UFAD) area

Ceiling Treatments: Ceiling cavity paint, lighting, acoustical treatment, fireproofing steel beams, and sprinklers

Furniture: Difference between system-powered and conventional furniture

198

Comparison of electrical first costsCBE first cost model

$0.41$2.09

$0.38

$2.72$0.76

$1.91

$10.06$6.80

$10.06$6.80

$10.06 $6.80

$1.83

$1.78$1.83

$1.78$1.83

$1.78

-$2.27-$1.45 -$2.13

-$1.23-$3.00

$0

$2

$4

$6

$8

$10

$12

$14

$16

OH: Pow

er po

le, po

wered

UFAD: Con

venti

onal,

non-p

owere

d

UFAD: Con

venti

onal,

powere

d

UFAD: Mod

ular, n

on-po

wered

UFAD: Mod

ular, p

owere

d

UFAD: Mod

ular, n

on-po

wered,

RF labo

r

Elec

tric

al c

ost,

$/G

sf

-$20-$18-$16-$14-$12-$10-$8-$6-$4-$2$0

Workstation - LaborWorkstation - MaterialV&D - LaborV&D - MaterialElectrical - LaborElectrical - Material

Cost differential, $/Gsf

Fred Bauman, CBE 34


199

When to Use Underfloor Air?

Office buildings -- all are possible but best for:Open office plans

Owner Occupied Buildings

Dry, Mild ClimatesEnergy benefits best in mild climates without high humidity levels – little or no chiller plant savings in humid climates

200


Spec Office Buildings – not as commonGrowing number of successful projects in recent years

Multiple tenants with diverse loads and full height walls may be a problem depending on system design

If first costs are higher than conventional systems, it is important to developer for UFAD building to command higher rents

201


Churches, Theaters, Auditoriums True displacement if supplied under seats at low velocity

Trading Floors

Tall spacesBanks

In recent years, increased number of projectsLibraries

Schools

Court Houses

Institutional

Wrap-Up,Conclusions

2:45 – 3:00

203

Last Thoughts…

Significant energy savings possibleDepends strongly on climate

Depends on designing and operating the systems correctly

More Research NeededLoad calc’s

Stratification

Underfloor plenum

Energy Simulation will be KeySlab, plenum, stratification

204

Underfloor Air Technology Websitewww.cbe.berkeley.edu/underfloorair

Objective:Develop and maintain website dedicated to providing a complete and unbiased description of underfloor air distribution technology

Audience:- engineers and architects- building owners- developers- CBE partners and clients- manufacturers and rep’s- facility managers- corporate real estate- researchers

Fred Bauman, CBE 35


205

Underfloor Air Technology Website

Key Features:

- simple graphical tools highlighting basic concepts

- technical overviews explaining process, benefits and limitations

- detailed summaries of research on UFAD and related technologies

- guidelines for applying the technology

- case studies of existing systems

206

Current Research by CBE

Design toolsWhole-building energy simulation program (EnergyPlus):Ongoing 3-year project sponsored by California Energy Commission (CEC), U.S. DOE, CBE, and York (completion in summer 2006)

Cooling airflow design tool:Ongoing project sponsored by CEC and CBE (completion in Nov. 2006)

Field Studies -- Whole-building performance dataOngoing field study of Calif. State office building sponsored by Calif. State Dept. of General Services (completion in Dec. 2006)

Cost analysis toolOngoing 4-year project sponsored by U.S. GSA to develop first and life-cycle cost model comparing UFAD with OH systems (completion in Fall 2006)

207

What is EnergyPlus?

All-new fully integrated building & HVAC energy simulation program

Based on best features of BLAST and DOE-2 plus new capabilities

Designed for easy expansion

Public: open to all developers

Free download of latest version of EnergyPlus at www.energyplus.gov

208

Current EnergyPlus model

Temperature

Ceiling plenum

Conditioned space

Well-mixed, uniform temperature in conditioned space

Overhead system

209

New EnergyPlus UFAD model

Temperature

Ceiling plenum

Room air stratification modeled as two zones separated at

stratification height, h

Underfloor plenum

Upper, stratified zone

Lower, occupied zoneh

SAT

Stratification height

210

Recent Publications

"New Design and Operating Guidelines and Tools for UFAD Systems." HPAC Engineering Webcast Series -- March 1, 2006; www.hpac.com."Heat Transfer Pathways in Underfloor Air Distribution (UFAD) Systems,“ F. Bauman, H. Jin, and T. Webster.ASHRAE Transactions, Vol. 112, Part 2."Testing and Modeling of Underfloor Air Supply Plenums.“H. Jin, F. Bauman, and T. Webster.ASHRAE Transactions, Vol. 112, Part 2."Design Guidelines for Stratification in Underfloor Air Distribution (UFAD) Systems." T. Webster and F. Bauman.HPAC Engineering, June. http://hpac.texterity.com/hpac/200606/?pg=8"Design Guidelines for Underfloor Air Supply Plenums."F. Bauman, T. Webster, and H. Jin.HPAC Engineering, July.http://hpac.texterity.com/hpac/200607/?pg=30

Fred Bauman, CBE 36


211

Conclusions

Large and growing interest in underfloor air distribution

More information and experience is needed comparing UFAD to conventional overhead systems

Developments are underway addressing technology needs

Research on key fundamental issuesNew and revised design guidelines and toolsCommissioning, operating, and “tune-up” (recommissioning) guidelinesImproved training of construction and operations personnel

Greater familiarity and understanding within building industry

Questions?

Fred [email protected]

CBE websitewww.cbe.berkeley.edu

Underfloor air technology website www.cbe.berkeley.edu/underfloorair

CBE occupant survey websitewww.cbesurvey.org

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