Designing UFAD Systems Betterbricks Workshop, September 7-8, 2005

Designing UFAD Systems BetterBricks Workshop, September 7-8, 2005

Acknowledgments Designing Underfloor Air Course Development Distribution (UFAD) Systems Taylor Engineering

Allan Daly Workshop for BetterBricks Pacific Gas & Electric Co. Cascadia Region of Green Building Council Puget Sound / Oregon Chapters of ASHRAE ASHRAE Seattle – Sept. 7, Portland – Sept. 8, 2005 Projects, Images Arup, Flack + Kurtz, Nailor Industries, Fred Bauman, P.E. EH Price, Tate Access Floors, Center for the Built Environment, York International University of California, Berkeley

Agenda 9:00-9:10 Opening Comments 9:10-9:30 Introduction 9:30-10:10 Diffusers and Stratification 10:10-10:50 Underfloor Plenums Introduction 10:50 -11:05 Break 11:05-11:45 Load Calculations, Energy 11:45-12:00 Comfort and IAQ 12:00 -1:00 Lunch 9:10 – 9:30 1:00-1:20 Horizontal and Vertical Distribution 1:20-1:35 Commissioning and Operations 1:35-1:50 Post-Occupancy Evaluations 1:50-2:05 How to Decide to Go with UFAD? 2:05-2:15 Wrap-Up, Conclusions 2:15 -2:30 Break 2:30-4:00 Panel Discussion 3

CBE Organization CBE Industry Partners

Industry/University Cooperative Research Center (I/UCRC) Armstrong World Industries Skidmore Owings and Merrill Steelcase, Inc. National Science Foundation provides support and Arup* evaluation California Department of Syska Hennessy Group General Services Tate Access Floors Inc.* Industry Advisory Board shapes research agenda California Energy Commission Taylor Engineering Team: Semi-annual meetings emphasize interaction, shared goals • Taylor Engineering Charles M. Salter Associates and problem solving • Guttmann & Blaevoet E.H. Price Ltd. • Southland Industries • Swinerton Builders Flack + Kurtz, Inc. Trane HOK U.S. Department of Energy (DOE)* Keen Engineering, Inc. U.S. General Services Pacific Gas & Electric Co. Administration (GSA)* York International Corporation RTKL *founding partner 5 6

Overhead System Underfloor air distribution system

55°F-57°F

61°F-65°F

7 8

Underfloor vs. Conventional Potential UFAD Benefits Air Distribution System Design Issues

Improved occupant comfort, Underfloor air supply plenum productivity and health Air supplied into occupied zone near floor level Improved ventilation efficiency and indoor air quality Higher supply air temperatures (for cooling)

Reduced energy use Allows for occupant control Properly controlled stratification leads to reduced energy Reduced life-cycle building costs use while maintaining comfort

Improved flexibility for Reduced space sensible heat load building services Perimeter zone solutions are critical Reduced floor-to-floor height in new construction Access floor improves flexibility and re-configurability

9 10

Room Air Stratification Current Barriers to UFAD Technology (cooling operation)

Lack of familiarity by building industry

Higher first costs

Need for design guidelines and tools

Fundamental research needed on key issues

Room air stratification

Underfloor plenums

Energy performance

Thermal comfort and ventilation effectiveness

Problems with applicable standards and codes

11 12

Floor Construction Integrated Service Plenum

13 14

Underfloor Air & Power Underfloor HVAC Concept

PLUG & PLAY VAV Modular POWER and Diffuser Wiring CONTROLS

15 16

ASHRAE Research Project RP-1064: ASHRAE UFAD Design Guide UFAD Design Guide

CONTENTS (243 pp.) Project start: September 1999 1. Introduction 9. Perimeter and Special Primary author – Fred Bauman 2. Room Air Distribution Systems Contributing author – Allan Daly 3. Thermal Comfort and 10. Cost Considerations Indoor Air Quality 11. Standards, Codes, and Sponsored by ASHRAE and CBE 4. Underfloor Air Supply Ratings Plenums Technical oversight by TC 5.3, 12. Design Methodology 5. UFAD Equipment Room Air Distribution 13. Examples 6. Controls, Operation, and Guide published by ASHRAE in Maintenance 14. Future Directions December 2003 7. Energy Use 15. Glossary Available from ASHRAE bookstore 8. Design, Construction, and 16. References and Commissioning Annotated Bibliography Developed ASHRAE Professional 17. Index Development Seminar (PDS) 17 18

Development of UFAD Design Guide Current status of UFAD technology

Design Guide material Strong interest due to several attractive features

Current database of UFAD projects in North America Research (laboratory, field, simulation) ~300 installations Design experience (literature, interviews, case studies) ~50-55 million ft2

Manufacturer’s literature Routinely considered as HVAC design option

Includes UFAD and closely related task/ambient conditioning (TAC) systems Ongoing research and experience in the field are generating new and improved information Covers topics in which important differences exist between UFAD and conventional overhead design Problems found in completed UFAD installations are often the same as those found in overhead buildings Identifies areas where more work is needed Conservative design

Poor construction practice

Inadequate commissioning, controls, and operation

19 20

Raised floor and UFAD adoption How Many UFAD Projects are Installed?

Through 2000, approximately 80 projects ¾ 1995: Less than 3% of 20% representing some 20 million sq ft in US. new office buildings had 16% raised floors, UFAD a Raised Floor Between 2000-2002, the number of new projects “fringe” element UFAD 12% represented another 25 million sq ft.

¾ 2002: 7% of new offices 8% CBE currently maintains database of North used raised floors, 15% of these with UFAD American UFAD projects with over 300 4% installations representing 50-55 million sq ft. systems. % of New Office Construction

0% ¾ 2004: 14% -15% have 1995 1997 1999 2001 2003 2005 The jobs are getting larger. The Bank One Center raised floors, ~ 45% of Year in Chicago (1.5 million sq ft) was completed in these with UFAD 2003 and several more projects over 1 million sq ft systems. are now in design or under construction.

21 22

Diffuser types

Variable area (VA)

Swirl Diffusers and Stratification

9:30 – 10:10

Swirl, horizontal discharge

Linear bar grille

Swirl Diffusers Personal control of swirl diffuser Rotate face plate

Swirl floor diffuser

25 26

Personal control of swirl diffuser Individual Plenum Box

27 28

Office cubicles

Too many!

One diffuser per workstation 29 30

Variable-Area Diffuser

Proprietary Product

31 32

Variable Air Volume Performance Bar Grilles in Perimeter

CONSISTANT VELOCITY - VARIABLE VOLUME Maintain constant discharge velocity even as air reduces

33 34

Perimeter solution: Underfloor variable-speed fan-coil Variable Speed Fan-Coil Control

130°F Max Fan Speed

Design Discharge Air Design Airflow Fan Speed Temperature Setpoint Return Air Plenum Airflow

Glazing Fan Speed Fan Return Air Grille Airflow 30% Design 30% Design Airflow T Fan Speed No U/A diffusers Fan Speed in perimeter zones Heating Coil Lowest Possible Linear Bar Fan Speed Raised Access Floor Diffuser (~15% Max Fan Speed) Minimum Airflow (due to 60°F pressurized Fan Coil w/ ECM motor plenum) Heating Loop Output Deadband Cooling Loop Output

Flex Duct 35 36

Perimeter solution: Underfloor variable-speed fan-coil

37 38

Perimeter solution – variable-area diffuser Perimeter solution – variable-area diffuser Cooling mode Heating mode

39 40

Task/Ambient Conditioning Systems Diffuser Code Compliance

Desktop control for maximum In the past, technically only all-metal diffusers could meet all code occupant comfort control flame spread and smoke ratings

Relatively rare in practice 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)

41 42

Room air stratification (cooling operation) Overhead Air Distribution System

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

43 44

Displacement Ventilation System Underfloor Air Distribution System

Minimize mixing in occupied zone Increased mixing up to throw height (TH) Stratification height (SH) separates upper and lower zones Diffuser throw below stratification height (SH)

45 46

Underfloor Air Distribution System Air Patterns

displacement

swirl

Diffuser throw above stratification level (SH)

47 48

Diffuser Comparison Room Air Stratification Testing

Approach Full-scale laboratory tests of commercially available floor Vertical Throw diffusers in realistic office setting. Discharge to Clear Zone Study impact of various design and operating parameters Model Setting Airflow 50 fpm Radius on room air stratification (RAS). [ft3/min] [ft] [ft] Significance Control of stratification is crucial to: Vertical 100 4 - 6 1.5 Swirl Vertical 75 2.5 - 4.5 1.5 Proper design System sizing Variable Vertical 150 8 2.0 Area Full Spread 110 5 4.5 Energy efficient operation Vertical 75 / ft 25 - Thermal comfort Bar Vertical 40 / ft 18 - Indoor air quality

49 50

Stratification test results Results – Interior office, swirl diffusers Effect of airflow rate: constant load, swirl diffusers, interior zone

ASHRAE Std.55-2004 5°F ∆T 11 RAS profiles for high room load, 6 workstations

10 Normalized to 65°F SAT and common deltaT 9 1.0 cfm/sq. ft 10 8 0.6 cfm/sq. ft 9 Swirl diffusers Delta T = 8°F Delta T = 13°F 8 7 0.3 cfm/sq. ft 7 6 Low room 6 temperature 5 High room temperature 5 Height, ft 4 Height, ft Height, 4 3 High throw, 2 diffusers 3 2 Low throw, 8 diffusers Still satisfies vertical temperature High throw, 2 diffusers 2 1 difference (5°F) with 40% less air Low throw, 10 diffusers 1 Lowest throw, 7 DV diffusers 0 69 70 71 72 73 74 75 76 77 78 79 80 81 82 0 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 Room Temperature, °F Room Temperature, °F 51 52

Stratification Test Results Variable Area vs. Swirl Effect of supply air temperature: constant load, swirl diffusers, interior zone

VA Diffuser 11 10 9 8 Swirl Diffuser 7 6 SW-1 5 SW-2

Height, ft Height, 4 VA-1 3 VA-2 2 1 VA-3 0 69 70 71 72 73 74 75 76 77 78 79 80 81 82 Room Temperature, °F

Diffuser Room Room flow rate, 50 fpm Source: ASHRAE Load Airflow (% of Throw Journal May 2002 Test W/ft2 cfm/ft2 design) ft VA-1 2.6 0.8 70% 7 VA-2 2.9 0.8 30% ~7 VA-3 1.8 0.4 40% ~7 SW-1 2.5 0.6 90% ~4 SW-2 2.7 0.6 40% ~2 53 54

RAS Testing Results RAS Testing Results (Cooling performance) (Perimeter zone cooling)

The amount of stratification is primarily driven by Key perimeter zone issues room airflow relative to load, and throw height. Supply air temperature

Stratification will increase as room airflow and/or diffuser Diffuser throw height, airflow rate, amount of mixing throw height are reduced for constant heat input. Blinds up or blinds down 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 Net effect is that cooling air quantities in (increased fan energy, and lower RAT). perimeter zones can be in the range of 25% less to 15% greater, depending on the amount of Optimized control strategies should promote stratification (reduce airflow requirements), while balancing this with stratification and other operating conditions. comfort considerations (∆T < 3-4°F in occupied zone).

Due to stratification, consider increasing thermostat setpoint by 1-2°F, especially in interior zones.

55 56

Stratification (in practice) Controlling Room Air Stratification

Guidelines 80 Monitored Data from an Underfloor System Sensor Locations Promote stratification (reduce airflow requirements), while Perimeter Office 78 10' 1st floor, east perim maintaining comfort: ∆T < 3-4°F in occupied zone. 8' 6' Don’t be too conservative! Airflow should be no greater than 76 4' OH systems. 2' 74 0' Provide controls to reduce airflow to interior (rather than raise setpoint only) in case sizing is too conservative.

mixing Technology needs stratification 70 during during cooling heating Cooling airflow design tool mode mode 68 Impact of stratification on thermal comfort

6amnoon 6pm Identify thermostat control strategies 66 Tue 8/22 Tue 57Wed 8/23 58

Underfloor Air Supply Plenums

Underfloor Plenums Room

10:10 – 10:50

Return Plenum

Plenum Design Variations Airflow Performance Issues

Pressurized plenum Objective – deliver desired amount of air

Passive diffusers Pressurized vs. zero-pressure

Most common approach and focus of current practice Reduced static pressure

Plenum height (obstructions) Zero-pressure plenum Size of plenum zone Active (fan-powered) diffusers Air leakage Not as popular due to perceived higher costs Plenum inlet conditions Fully ducted Inlet velocity Inlet direction (open, vanes, plates) Not as popular due to high cost and lack of flexibility Location in zone Most designs are hybrid solutions Number of inlets in zone

61 62

Underfloor Air Supply Plenums Research Results Full-Scale Plenum Test Facility

Phase 1 – Airflow Performance

Plenum inlet 4" x 14" Floor grills Objective (typical) Fan 5' 10' 10' 10' 10' 10' 10' 10' 5' Investigate practical plenum configuration issues, including Flow measuring minimum plenum height, for which acceptable airflow station 23"x 23" performance can be achieved in pressurized underfloor Duct plenums.

M M M M M 40' Approach Empirical experiments in full-scale underfloor air supply 4' Underfloor barrier plenum test facility. M M M M M

80' Removable Measurement Obstruction #1 floor panels (2) point (typical) Obstruction #2 Plan View 24' 19' 14' 10' Raised Floor

Concrete Slab Section View 63 64

Plenum Schematic Cross-Section Results

Airflow delivery is very uniform from an 8-inch

Plenum Schematic Cross-Section pressurized underfloor plenum over a full range of 2 Finish Floor Level supply volumes (0.5-1.5 cfm/ft ), even at a distance of 80 feet from the plenum inlet.

1-inch Floor Panel Uniformity (less than 10% variation) is preserved 2" 3" for solid obstructions with only 1.5 inches of clear

1" space.

7" 2" 2"

2" 2" Polystyrene Blocks

Concrete Slab

65 66

Air Flow Ratio: 8-inch plenum Publication

“How Low Can You Go?” 130% Air Flow Performance of 1.5 cfm/sf Low-Height Underfloor Plenums 120% 1.0 cfm/sf

0.5 cfm/sf F. Bauman, P. Pecora, and T. Webster

110% Center for the Built Environment University of California Berkeley, California 100% October 1999

90% Delivered Ratio Air Flow (Measured flow/Uniform flow) flow/Uniform (Measured

80% PDF available from: www.cbe.berkeley.edu/underfloorair

70% 0 1020304050607080 Distance from Fan Inlet (ft) 67 68

Smoke Test Plenum Air Leakage Air leakage between Floor Panels

Air leakage from a pressurized plenum may impact energy use and can impair system performance if not accounted for.

Air Leakage Floor Diffuser Floor Panel

Types of leakage

Leakage between floor panels

Leakage due to poor sealing and construction

69 70

Air Leakage Test Setup Carpet Tile Configurations

Aligned Offset

71 72

Air Leakage between Floor Panels Thermal Performance Issues Carpet Tile Configurations Pressurized Plenums

Objective – deliver air at the desired temperature using a minimum amount of energy 1 Plenum inlet conditions 0.9 ) 2 0.8 Supply air temperature Bare panels 0.7 Inlet velocity and direction Aligned carpet 0.6 Offset carpet Thermal decay 0.5 0.4 Heat transfer coefficients (slab and panels) 0.3 Velocity and residence time of air in plenum 0.2 Air Leakage (cfm/ft Leakage Air Temperature profile in slab and floor panels 0.1 Temperature on underside of slab 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 Thermal storage strategies (nighttime pre-cooling) Pressure (in. w.c.)

73 74

Temperature variations in underfloor plenum Ongoing Research on Underfloor Plenums

Phase 2 – Thermal Performance

CFD model of underfloor plenum

Full-scale experiments

Temperature [F] Validate model vs. test facility

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

75 76

Effect of Plenum Inlet Conditions Plenum Air Temperature – CFD Model

Focused jet Diffusers a) b)

Diffusers

Vanes

Inlet Inlet

Plan view of plenum air flow patterns:

(a) without inlet vanes, (b) with inlet vanes (°F) 77 78

CFD model: Particle visualization Full-Scale Plenum Test Facility

Temperature (°F)

79 80

Underfloor plenum guidelines

Airflow delivery and pressure distribution Quite uniform across open pressurized plenum zone Break Leakage

Account for leakage into occupied space in design airflow calculations 10:50 – 11:05

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 important

Does UFAD Require More Air?

Assuming complete mixing: Load Calculations, Overhead: Underfloor: Supply Temp: 55 F Supply Temp: 63 F

Energy Room Setpoint: 75 F Room Setpoint: 75 F Space Heat Load: 17,297 Btu/hr Space Heat Load: 17,297 Btu/hr

11:05 - 11:45 CFM = 17,297 Btu/hr = 786 CFM CFM = 17,291 Btu/hr = 1,335 CFM

1.1 Btu/hr-cfm-F x (75F-55F) 1.1 Btu/hr-cfm-F x (75F-63F)

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

Overhead Air Distribution System Underfloor Air Distribution System

Mixing system tries to maintain uniform temperature Increased mixing up to throw height (TH) and ventilation conditions throughout space Diffuser throw below stratification height (SH)

85 86

Heat Transfer in UFAD Systems Energy Flows in Stratified UFAD System

Background

In 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).

Question

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

Approach

Assumption of perfect mixing is no longer valid

Simplified first-law (energy balance) model

Publication

Submitted to ASHRAE Transactions 2007

87 88

Cooling Operation of Overhead System Simplified Model – Heat Transfer Pathways

Slab-supply plenum conduction/convection Slab Return 78°F T Return-slab convection Plenum return Ceiling-slab radiation Return-ceiling convection Treturn Extraction Tceiling 100% Ceiling-floor radiation Room Heat gain into space T = 72°F Raised Floor room, near floor 100% Panels Tcarpet Floor-room convection

Floor-supply plenum conduction/convection Supply 0.6 cfm/ft2, 65°F T Plenum plenum Slab-supply plenum conduction/convection Slab

Return Plenum Treturn

89 90

Predicted Distribution of Room Cooling Load EnergyPlus Modeling 180 29.1

24.4 160 24.3 76 Baseline results – hung ceiling Considering Radiation is 24.3 140 24.2 KEY to making sense out 23.9 23.8 of heat flows in UFAD 75 systems (and all 120 systems). Through slab Heat gain Extraction 100 ∆T =13 into space 29% 57% Internal Loads Example room 2 100% (3.6 W/ft ) ∆Tsystem=20 80 75 23.8 23.6

Through floor Tsupply = 56 60 14% Tplenum = 63 Troom = 75 Treturn = 76 40 63 17.4 20 22.5 Total into plenum 18.8 System ∆T = 76-56 = 20 13.4 43% 17.4 Room ∆T = 75-63 = 13 56 17.8 0 16.2 10 15 20 25 30 91 92

Load Calculation/Energy Software Tools Load Calc’s: What to do?!?

Common load/energy calculation programs Designers need to understand the physics of these systems Trane Trace 700/Load 700

Carrier HAP “Standard” load calc’s seem to work

Elite (CAVEAT CAVEAT CAVEAT)

Wrightsoft RSC Must design systems that can react to dynamic DOE2.1, 2.2 load conditions

VAV system operation important No Underfloor Model in any of them! Resets seem to be very helpful For load calculations, air volumes seem to work out to be the same as overhead calculations (so far…) Systems must be commissioned to make sure they work EnergyPlus UFAD system development underway!

93 94

UFAD: Good Energy Performance More 100% Free Cooling

Cooling Energy Mechanical cooling not required

Free Cooling due to warm supply air temperatures

Mechanical Cooling

65oF <=65oF Cooling Coil Supply Air Temperature Fan Energy Outdoor Air Temperature is OFF

Air Pressures

Air Volumes

Reheat Energy

Lower ∆T

Lower Air-Volumes 85oF Return Air Temperature

95 96

More Integrated Economizer Cooling Energy Advantages in the San Francisco Area

San Francisco Outdoor Temperature Distribution Higher return air temperature keeps (Dry Bulb temperatures between 8am and 8pm) system at 100% outdoor air longer 100% Economizer 2217 Hours 300

65oF 65oF to <85oF Cooling Coil Supply Air Temperature 250 Outdoor Air Temperature is On

200

150 Hours

100

o 85 F 50 Return Air Temperature

0 83 87 91 93 95 79 81 85 89 33 37 39 41 43 45 47 49 53 55 57 59 61 63 65 67 69 71 73 75 77 51

97 Outdoor Dry Bulb Temperature [F] 98

UFAD in Other Climates Economizer Savings Summary

600

500 Example Sensible Cooling Energy as a Function of 400

300 Outside Air Temperature

200 35,000

100 30,000 0

5 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 2 - 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 600- -20 -15 -10 100 25,000 500

400

[Btu] 20,000 300 OH system 200 15,000

100 Cooling UF system 0 10,000 0 5 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 2 1 1 -5 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 600-25 - - - 10

500 5,000

400

300 0

200 50 55 60 65 70 75 80 85 90 95 100 o 100 Outside Air Temperature [ F] 0

0 5 0 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 2 1 1 -5 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 -25 - - - 10

HVAC Design Fundamentals Design HVAC 99 100

Mechanical Cooling Energy Savings Dehumidification

Chiller energy Chilled water supply decreases as the temperature is 50oF 40oF chilled water supply 62oF determined by the 52oF temperature lowest supply-air increases – the temperature needed. compressor does less work 65oF If dehumidification is 55oF needed, this is likely to be 55oF or lower.

65oF 55oF Affects both mechanical and free cooling.

101 102

Mixing OH and UFAD Systems System Type

Most UFAD perimeter systems still use reheat coils constant-speed or variable-speed fan units Chilled water supply HW or electric resistance heat temperature is 40oF Unducted – supplies underfloor air for cooling determined by the 52oF lowest supply-air VAV change-over air handlers are another more efficient temperature needed option

Separate air handler per exposure 65oF If standard OH Controlled similar to “VVT” system systems are used, this is likely to be 55oF.

55oF Affects both mechanical and free cooling.

103 104

Reheat Energy Structural Slab Thermal Storage

Building physics and anecdotal evidence suggest there is a strong coupling of plenum air and slab. Examples Item Units Symbol / Equation OH UFAD

Heating Load [Btu/h] Qh 10,000 10,000 No validated mathematical models exist that can T System Supply Air Temp [F] sys 55 63 be used in design. Room Heating Setpoint [F] Tset 70 70

Room Supply Air Temp [F] Tsupply 90 110

Supply Air Flow [CFM] Qh / (1.1 x (Tsupply-Tset)) 455 227 CBE, CEC, UCSD, and DOE working on it (EIEIO).

Reheat [Btu/h] CFM x 1.1 x (Tset - Tsys) 7,500 1,750 23%

105 106

Reduced Fan Power Fan Energy Savings: Air Volumes

Calculations and practice suggest that UFAD systems do Underfloor plenum is the primary air distribution not require more air than OH systems due to stratification route But…

UFAD systems use less ductwork than OH There are many unknowns associated with load calc’s systems It appears that built projects in case studies provide too much air Primary fan pressure reduced 1/2 to 1 in. H O, a 2 Further research will allow us to design for reduced air reduction of about 25% volumes Substantial energy savings on primary fan power possible, however this may be offset by fan- powered boxes or terminals used in perimeter zones

107 108

Thermal Comfort Variations in Individual Preferences

Clothing

Comfort and IAQ Activity level

Body weight & size

11:45 – 12:00 Personal preferences

110

Thermal Comfort Personal Control

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

Less control = more hot/cold complaints Light office activity, light jacket, slacks Sedentary, Skirt, blouse, pantyhose

111 112

Thermal Comfort Occupant Control Issues

Traditional approach Supply outlet design (swirl, jet)

Satisfy up to 80% of building occupants Passive (pressurized plenum) vs. active (local fan- driven) diffusers Underfloor approach

Allow personal control of the local thermal environment  Understandable and easy to use satisfy up to 100% of occupants  reduce occupant complaints Frequency of adjustment

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

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

113 114

Comfort Standards (Impact of stratification on thermal comfort) Ongoing Comfort Research

CBE advanced thermal comfort model indicates ASHRAE 55 and ISO 7730 that greater stratification (> 5°F) may be define a 5°F (3ºC) limit on acceptable in middle of comfort zone. vertical air stratification The limit was based on New research is needed to define comfort criteria Olesen’s study in 1979 on 16 in stratified environments college students 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

115 116

Room Air Stratification Indoor Air Quality (cooling operation)

Traditional approach

Provide uniform ventilation throughout space

Underfloor approach

Fresh 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)

117 118

Air Change Effectiveness (ACE) Indoor air quality

ACE = age of air at return (τreturn) / age of air at breathing level (τbl) Air change effectiveness (ACE)

Overhead (OH) systems (0.8 heating, 1.0 cooling)

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

τbl 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

119 120

Research needed

Ventilation performance in UFAD systems

Lack of quantitative data on ventilation performance of current-generation UFAD systems Lunch ASHRAE TC 5.3 is preparing research work statement for proposed laboratory and computational fluid dynamics (CFD) study of ventilation performance of stratified systems (UFAD and displacement ventilation) 12:00 - 1:00

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

121

Plenum Distribution Criteria

General, uniform air distribution

Horizontal and Vertical Relatively equal supply air temperature to each Distribution diffuser Relatively equal pressure in plenum 1:00 – 1:20

124

Horizontal Distribution Layout Example: Initial Plan – Large amount of ductwork

125 126

Horizontal Distribution Layout Example: Final plan

employs multiple 50 foot shafts to reduce radius ductwork in the Shafts floor

127 128

“Air Highways” “Air Highway” Cross Section

129 130

Large Air Highway Air Highway Construction

131 132

Air Highway Goals Air Highway Limitations

Lower costs Questionable actual cost savings

Less sheet metal Familiarity of construction by floor contractors, general contractor Lower labor rates of floor installers Code equivalence to a duct

Lower pressure drop Crossing corridors

Larger effective duct area Construction coordination

Not complete until floor tiles installed

Reduced coordination and conflicts Damage by other trades

Leak-free Limited pressure capability Leakage!!!!

133 134

The need for Plenum Dividers Plenum Dividers

Sheet metal plenum dividers subdivide UF plenum Maximum 25000 ft2 area per zone Purpose: Plenum Dividers

Provide more interior control zones

Reduce length of air travel to perimeter UFTs Reduced temperature degradation

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

135 136

Recommendations

Use as little underfloor ductwork as possible

Minimize cost

Minimize conflicts

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

Use many vertical shafts to try to eliminate horizontal 1:20 – 1:35 ductwork

Cost of fire/smoke dampers offset by eliminated ductwork

Reduced velocity leaving shaft, reduces noise

137

Plenum Air Leakage Acceptable Leakage Rates

Conduct leakage tests in underfloor plenum Construction quality leakage

Blower panel with variable-speed test fan 2 Not to exceed 0.05 cfm/ft at 0.05 in H2O 2 Maintain design plenum pressure (e.g., 0.05 in. H2O) (e.g., 1,000 cfm for a 20,000 ft floor plate)

Test #1 – Total leakage Floor leakage

Floor panels, electrical outlets, carpet tiles installed according 2 to typical design specifications Not to exceed 0.10 cfm/ft at 0.05 in H2O (e.g., 17% leakage for an interior zone with 0.6 cfm/ft2 Seal all diffusers design airflow) Test #2 – Construction quality leakage Consider testing a full-scale mock-up prior to Seal all openings and gaps on raised floor surface construction. Apply corrections and sealing Floor leakage methods to remaining underfloor plenums and test again. Subtract Test #2 result from Test #1 result

139 140

Adjusting Stratification Airflow and Room Air Stratification (at peak load)

No cooling airflow design tool yet available Adjust

Airflow quantity Systems are commonly oversized, often as a result of over-estimation of design loads Plenum pressure max setpoint

Conduct measurements of vertical temperature # of diffusers profile during fully loaded conditions TStat setpoint

Use “stratification measurement tree” consisting of string or pole with several temperature sensors at regular intervals Goal Prior to measurements, operate building long enough (up to one week) to ensure thermal mass of structural slab is in equilibrium ∆T ~ 3-4°F in occupied zone

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

141 142

Other Considerations

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

Building operators must be properly trained on UFAD design Post-Occupancy and operation Evaluations 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 1:35 – 1:50 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 143

CBE occupant satisfaction survey Survey implementation

CBE’s occupant satisfaction survey offers a Survey systematic, cost-effective notification way of measuring how via email satisfied occupants are with their workplace Occupants environments. respond to web-based survey Data sent to SQL server database Results reported online 145 146

Satisfaction with indoor air quality Satisfaction with thermal comfort Occupant survey results Occupant survey results

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

-3 0 3 -3 0 3

+0.88 mean satisfaction +0.23 mean satisfaction 7 UFAD bldgs, 1,344 responses 7 UFAD bldgs, 1,344 responses

+0.23 mean satisfaction -0.21 mean satisfaction 152 overhead bldgs, 25,749 responses 152 overhead bldgs, 25,749 responses

Reference: www.cbesurvey.org Reference: www.cbesurvey.org

147 148

Satisfaction with lighting Satisfaction with acoustic quality Occupant survey results Occupant survey results

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

-3 0 3 -3 0 3

+0.72 mean satisfaction -0.16 mean satisfaction 7 UFAD bldgs, 1,344 responses 7 UFAD bldgs, 1,344 responses

+1.31 mean satisfaction +0.18 mean satisfaction 152 overhead bldgs, 25,749 responses 152 overhead bldgs, 25,749 responses

Reference: www.cbesurvey.org Reference: www.cbesurvey.org

149 150

Satisfaction with cleanliness CBE UFAD project database Occupant survey results www.cbe.berkeley.edu/underfloorair/casestudies.htm

~300 projects in North America Web-based questionnaire collecting key building characteristics How satisfied are you with the general cleanliness of the overall building? ~32 buildings under active study; 13 have completed operations section of questionnaire

-3 0 3

+1.45 mean satisfaction 7 UFAD bldgs, 1,344 responses

+0.94 mean satisfaction 152 overhead bldgs, 25,749 responses

Reference: www.cbesurvey.org

151 152

UFAD building operations questionnaire UFAD building operations questionnaire Completed by facility managers Completed by facility managers

Based on your knowledge of how the UFAD system has been Based on your experience with this building, indicate how serious operating and your experience in other non-UFAD buildings, how of a problem the following have been: much better or worse is this building in comparison to conventional buildings with respect to: No problem Serious problem 3 0 -3 Mean Much better Much worse 3 0 -3 Mean Operations issue N response Operations issue N response Moisture, mold, related problems 13 2.08 Making changes to tenant space 13 0.92 Temp. stratification in occupied spaces 13 1.67 Energy use 13 0.67 Dust and dirt in plenum 13 1.25 Overall performance of UFAD system 13 0.62 Air leakage from panel joints 13 0.92

Hot and cold complaints 13 0.54 Plenum airflow and thermal decay 13 0.17

Effort and cost of maintenance 13 0.15 Air leakage from construction joints 13 -0.17

153 154

Cost considerations – UFAD vs. overhead

Accurate first and life-cycle cost estimates are crucial early How to Decide to in design process Added first cost of raised floor system can be offset (in part) by reduction in ductwork and electrical/ Go with UFAD? telecomm installation costs

Recent projects have demonstrated that first costs for UFAD can be very comparable to overhead systems 2 2 1:50 – 2:05 Range from $1.00-1.50/ft reduction to $4.00-6.00/ft 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

156

Relative costs Ongoing CBE UFAD Cost Analysis Project

Objective: Develop comprehensive first and $250 life-cycle cost model for UFAD systems

$200 Funded by U.S. GSA

Began summer 2002, ~$450K budget $150 A 1% Savings in Productivity Project status Î ~1 year payback $100 First cost model complete

Development of life-cycle cost model underway

$50 Complete model and total cost analysis complete by Office Building Cost per Square Foot Square per Cost Building Office September 2006

$- Cost of Labor Cost of Energy Incremental Cost of UFAD 157 158

Approach - Affected first cost elements Comparison of electrical first costs CBE first cost model

$16 $0 The model evaluates each affected element and computes the -$1.45 -$1.23 -$2.27 -$2.13 -$2 Cost differential, $/Gsf UFAD to overhead (OH) system cost difference $14 $1.83 -$3.00 $1.83 -$4 $12 $1.83 $1.78 $1.78 -$6 Access Floor: Installation of access floors & carpets $1.78 $10 -$8 Workstation - Labor Workstation - Material Façade & structure: Allowance for reducing floor-to-floor height $8 $10.06 -$10 $6.80 $6.80 $10.06 V&D - Labor $6 $10.06 $6.80 -$12 V&D - Material HVAC: Cooling and heating loads calculation for sizing and pricing -$14

Electrical cost, $/Gsf cost, Electrical $4 Electrical - Labor tenant area HVAC costs -$16 $2 Electrical - Material $2.72 -$18 Electrical: Power distribution and voice and data differences $2.09 $1.91 $0 $0.41 $0.38 $0.76 -$20 r d d d d d o re re re re re b Raised Core: Raised slab in core (non-UFAD) area e e e e e a w w w w w l o o o o o F p -p p -p p R , n l, n r, , le o a o a d Ceiling Treatments: Ceiling cavity paint, lighting, acoustical treatment, o n n n l re p , io , u e r l t r d w e a n la o o w n e u M p fireproofing steel beams, and sprinklers tio v d : - Po n n o n : e o M AD o H v C : F n n : D U r, O o A la C AD u Furniture: Difference between system-powered and conventional : F F d D U U o A M F furniture U : AD F U

159 160

When to Use Underfloor Air? When to Use Underfloor Air?

Office buildings -- all are possible but best for: Spec Office Buildings – not as common

Open office plans Growing number of successful projects in recent years

Owner Occupied Buildings Multiple tenants with diverse loads and full height walls may be a problem depending on system design Dry, Mild Climates If first costs are higher than conventional systems, it is Energy benefits best in mild climates without high humidity important to developer for UFAD building to command higher levels – little or no chiller plant savings in humid climates rents

161 162

When to Use Underfloor Air?

Churches, Theaters, Auditoriums True displacement if supplied under seats at low velocity Wrap-Up, Trading Floors Conclusions Tall spaces Banks 2:05 – 2:15 In recent years, increased number of projects

Libraries

Schools

Court Houses

Institutional

163

Underfloor Air Technology Website Last Thoughts… www.cbe.berkeley.edu/underfloorair

Significant energy savings possible Objective: Develop and maintain website dedicated to providing a complete Depends strongly on climate and unbiased description of underfloor air distribution technology

Depends on designing the systems correctly

More Research Needed Audience: - engineers and architects Load calc’s - building owners

Stratification - developers - CBE partners and clients Underfloor plenum - manufacturers and rep’s - facility managers Energy Simulation will be Key - corporate real estate - researchers Slab, plenum, stratification

165 166

Underfloor Air Technology Website Current Research by CBE

Key Features: Design tools

- simple graphical tools highlighting basic concepts Whole-building energy simulation program (EnergyPlus): Ongoing 3-year project sponsored by California Energy Commission - technical overviews explaining process, benefits (CEC), U.S. DOE, CBE, and York (completion in June 2006) and limitations Cooling airflow design tool: - detailed summaries of New project sponsored by CEC and others (completion in Nov. 2006) research on UFAD and related technologies Field Studies -- Whole-building performance data - guidelines for applying Ongoing field study of Calif. State office building sponsored by Calif. the technology State Dept. of General Services (completion in Dec. 2006) - case studies of existing systems Cost analysis tool

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

167 168

Conclusions Questions?

Large and growing interest in underfloor air Fred Bauman distribution [email protected] CBE website More information and experience is needed www.cbe.berkeley.edu comparing UFAD to conventional overhead Underfloor air technology website systems www.cbe.berkeley.edu/underfloorair

Developments are underway addressing CBE occupant survey website technology needs www.cbesurvey.org

Research on key fundamental issues

New and revised design guidelines and tools

Improved training of construction and operations personnel

Revised standards and codes as appropriate

Greater familiarity and understanding within building industry 169