high performance building facade solutions · building facade solutions 2 lawrence berkeley...

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Lawrence Berkeley National Laboratory

Eleanor Lee, Staff ScientistBuilding Technologies Department


Stephen Selkowitz, Joseph Klems, Robert Clear, DariushArasteh, Mike Rubin, Phil Haves, Michael Wetter, Jacob

Jonssen, Andrew McNeil, Tianzhen Hong, Christian Kohler, Robin Mitchell, Mehry Yazdanian, Kyle Konis, Windows

and Daylighting Group, Lawrence Berkeley National Laboratory

High Performance Building Facade Solutions

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Broad Context

• Great diversity; creative architectural and engineering solutions• U.S. History

– 37 years since the 1973 OAPEC crisis– Lots of forward progress but lots of steps backwards too: the political

environment supporting energy-efficiency has wavered • Today: The Perfect Storm

– Urgency: Climate change is happening (& finally acknowledged)– ARRA funding supports energy-efficiency measures, green jobs,

workforce training– Opportunity to make significant advances toward solving the GHG

problem by increasing building energy-efficiency, getting buildings off the grid, and improving the everday comfort and satisfaction of building inhabitants

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Inaction: Why?

• Doubt– How long will this Perfect Storm last? – Do we think we can make a difference on GHG?– Too hard, complex, and risky: do we really have to go

with such complicated solutions to achieve our goals?

• Reality– How do I convince the client?– How do I justify the added cost, especially in a

constrained economic environment?

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Context for Facades R&D: Prior Work (past 3+ decades)

• Criteria: Broadly applicable (<10% incremental increase in cost over conventional 2-5 year payback based on energy cost savings – ROI must compete with Wall Street)

• Objective: Develop low-cost, energy-efficient façade technologies for broad market deployment in commercial and residential buildings

– Near-term: Simple, turn-key, replacement technologies (50-70% of the market)

- Thermally-improved framing systems with reduced infiltration- Spectrally selective, low-emittance coatings on glass

– Long-term: Intelligent, integrated façade-lighting-HVAC systems (<1% of the market)

- Switchable, durable electrochromic windows- Local control solutions with minimal sensors, self-

commissioning, little to no O&M costs

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Context of Today (next 15-20+ years)

• Criteria: Broad deployment with life-cycle cost/ global cost approach to accelerate market adoption societal impacts + occupant productivity, health, and satisfaction with their environment

• Net Zero Energy Buildings Approach– Dynamic envelope-lighting-HVAC solutions– Global, optimized control with an intelligent, integrated envelope-

lighting-HVAC system working real-time with BMCS/ campus/ city/ region context

– Smart sensor networked grid (OEM $0.10/point $0.11/point?)– Facility + occupant-based control (user autonomy when appropriate)– Active components

- Switchable glazings- Motorized interior and exterior shading- Active daylighting systems- Active controls for natural or mixed mode ventilation and load

shifting/ thermal mass/ radiant heating & cooling strategies

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Potential Solutions (split between KISS + responsive)

• Hi-R facades– Aerogel– Vacuum glazings– Superwindows (R6+)

• Solar control– Ceramic fritted glass– Exterior metal scrims, fixed overhangs, fins– Automated exterior shades

• Daylight redirection/ lighting quality• Automated, intelligent facades

– Real-time HVAC-Lighting-Façade systems optimization – Daylight + view ↔ SHG + visual comfort/ performance– Low-energy cooling strategies

- Night-time ventilation + chilled ceilings- Double-envelope facades

– Demand response• Photovoltaic-integrated facades for on-site renewable energy

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0% savings: Code baseline: Low-SHGC windows and with manually-operated shades and lighting

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20% savings: Automated interior shades + DALI dimmable lighting systems

The New York Times Headquarters

Daylight “efficient” shading

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Annual Source Energy Use

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Lawrence Berkeley National LaboratorySouth zone, source kBtu/sf-floor-yr

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Lawrence Berkeley National LaboratorySouth zone, source kBtu/sf-floor-yr

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http://lowenergyfacades.lbl.gov

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Comfen output

OverviewPerformance Relative Cost Benchmarks Design Advisor

Thermal Comfort Daylight Penetration

Energy Façade Gain

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Lawrence Berkeley National LaboratoryKyle Konis, UCB/ LBNL

How do we reduce lighting energy use with daylight when there is glare?

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Low-e split blind (fixed relationship between upper & lower slats

Upper: horiz/ Lower: +30°Upper: -45 ° / Lower: 0° Upper: +60° / Lower: +closed

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Split reflective blind

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Diffuser above, blind below

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Lawrence Berkeley National LaboratoryAutomated roller shade

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Automated daylight blind: concave-up slats with mirrored coating in upper zone and light grey

finish in lower zone

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Sunlight-redirecting blinds

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Avg Annual Lighting Energy Use vs Visual Discomfort: Dynamic systems do better

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

auto-split-mir-VB1

ref-VB

split-opt-VB

diff-VB

auto-VB

split-VB

auto-RS

ref-RS

full power Percent ofdaywindow >2000cd/sqm

LPD (W/sf)

0.57 W/sf0.34 W/sf

0.31 W/sf

10% of day = 1.2 hours

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DGI Summary for 6 Test Conditions (Window View)

Auto-split-mir-VB Auto-VB Split-opt-VB Split-VB Diffuse-VB Auto-RS

Paired Reference

Test Condition

DGI of 16:20 = Just Acceptable, 20:24 = Just Uncomfortable, 24:28 = Just Intolerable, 28:36 = Intolerable

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07.23 08.21 10.08 11.09 11.30

Daily Composites…

Solstice to solstice composite, N = 14 days (clear)Test ConditionE

Diagnostics: Glare Source Composites

Glare Source Dx Dy Dz Steradians Luminance (cd/m^2) Indirect Illuminance (lux)1 0.88 0.30 -0.37 0.27 2771 11432 0.92 -0.37 -0.13 0.45 17993 0.18 -0.96 -0.20 0.01 14324 0.82 0.54 -0.21 0.00 35825 0.96 0.18 0.20 0.14 29406 0.92 0.38 0.11 0.02 31807 0.89 0.45 -0.01 0.02 25068 0.85 0.44 0.30 0.02 20709 0.83 0.51 0.21 0.02 276210 0.85 0.53 -0.01 0.02 246311 0.79 0.61 -0.08 0.02 237012 0.77 0.60 0.23 0.02 279113 0.76 0.64 0.08 0.02 270814 0.75 0.47 0.47 0.02 122615 0.84 -0.06 0.55 0.00 1295

RADIANCE Findglare output x 144 images

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Complex Fenestration Systems (CFS)

South NorthSource: St. Gobain/ Eckelt DLS COOLSHADE HR 32/9

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Definition: BRDFs and BTDFsbi-directional reflectance and transmittance functions

Image from Marilyne Andersen, 2004

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Lawrence Berkeley National LaboratoryWindows Testbed Facility, LBNL

Accuracy of spatial distribution of flux

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Basis Angle Projections

Klems basis projection 2° basis projection

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Phase II: Exterior shading systems (June 2008- June 2009)

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Exterior Venetian Blinds

Automated exterior blind Static 3-zone blind with bent slats

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3-zone exterior blindinterior and exterior automated roller shades

71%: peak 18 5 W/ft2-windowReference: Interior venetian blind blocking direct sun

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Visual Discomfort

3-zone: Visual discomfort due to high window luminance reduced from 34% of day down to 6% of day

Automated roller shade: 2% of day

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30-50% savings: Integrated facades and low-energy cooling

Nord LB, Hannover

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Definition of a smart building skin

Operable façade components: Motors or actuators for shading devices, light-redirecting elements, operable windows, or switchable glass coatings

Interior or exterior sensors that measure relevant quantities that are used by the controller

Control algorithms: Accepts input from sensors or computations then determines how to position the operable façade components

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If Glare and Solar Control is so important, Why not integrate this function into the glazing?

Switchable electrochromicglazings(dimmable via 0-3VDC)

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Human subjects study in LBNL windows test facility

(switchable electrochromicwindows)

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The New York Times Headquarters, New York, NY

• In 2003, The New York Times approached LBNL regarding feasibility of using automated shade and dimmable daylightingcontrol systems in their new headquarters building (1.2 Msf)

• Questions:– Cost versus potential

benefits? – Features and performance of

commercially-available systems?

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NYT Key Concerns: Optimizing Trade-offs

• Floor to ceiling, clear, low-iron, spectrally-selective low-e glass– Tv=0.75, SHGC=0.39, U-factor=0.28 Btu/h-ft2-°F– Horizontal ceramic tubes,18-inches off exterior face of

window

• Control system trade-offs with automated shading: – Direct sun control: thermal comfort with UFAD system +

visual comfort– Absence of glare (disability, discomfort, luminance ratios,

computer display visibility)– Reduced peak solar load (depending on fabric choice and

control)

– Maximize daylight (lighting energy savings, peak demand reduction)

– Maximize interior brightness, combat gloom– Maximize view out (meaningful stimuli, reduction of stress)– Preserve design aesthetic of a “transparent” façade

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Radiance model: floor plan view

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Approach: Test Energy/Comfort Performance in a Full-Scale Mockup

• Furniture, daylighting, employee feedback and constructability: ~450 m2, 4500 sf mockup

• Core Concerns:– Window glare (Tv=0.75)– Daylight harvesting potential

• Northwest – Southwest corner of a typical floor

• Investigate diverse technological solutions by multiple vendors

• Real sun and sky conditions in nearby climate zone, 6-month monitored period: winter to summer solstice

North

AB

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Mock-up InstrumentationIIluminance sensors

Workstation instrumentation at occupant position with LCD screen

– Luminance and illuminancesensors

– Webcams (10-min time lapse throughout the day)

• Quantified lighting energy savings, visual comfort, and control system behavior

• Surveyed occupant comfort and satisfaction

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Lawrence Berkeley National Laboratory9:00 AM

WestSouth

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Lawrence Berkeley National Laboratory1:00 PM

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State-of-the-shelf example• The New York Times Headquarters (specified in 2004)

– Automated shading- Motorized, automated roller shades for direct sun, daylight, glare, and view

control with manual override, scheduling, urban context, demand response- Centralized control +16 networked sensors/ floor + 8 roof-mounted

sensors, real-time, scheduling, model-based/ feedback heterogeneous control

– Dimmable lighting- Dimmable, reconfigurable zones, occupancy, scheduling, tuning, demand

response- First large-procurement of “DALI-enabled” ballasts: each fixture is

addressable & reconfigurable- Distributed control + 16 open-loop sensors/floor + occupancy sensors

– +10-20% incremental cost: competitive bidding, component engineering, turn-key commissioning tools

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Direct sun• 3%-open

shade fabric– direct

source glare

– ~black out shades needed

• But– More

opaque fabric will block more daylight

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Sky Glare can be a Problem as well as Direct Sun

East view South viewMeasured data

(cd/m2)12/15, 10:00AM

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Shades down (partial on south)

East view West view

Measured data (cd/m2)12/15, 10:00AM

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Luminance Measurements at Typical Workstations

1:3

1:3

1:3 remote

1:3

1:3

1:3

1:3

1:3 remote

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Window luminance: west, vernal equinox, config 3 or 4 sunny, Eglo.avg = 35-53 klux

For 10 days over the 6-month (solstice-to-solstice) monitored period, the west window luminance was greater than 2000 cd/m2 for 10-54 minutes of the day.

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Measured Average Daily Lighting Energy Use Savings

As of May 2008: Avg LPD = 0.35 W/sf

0%

20%

40%

60%

80%

100%

0 2 4 6 8 10 12 14distance from window (m)

daily

ligh

ting

ener

gy s

avin

gs (%

)

Area A west Area B west Area B south

B

B

A

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Simplify wiring and cabling to reduce install costs

photosensor

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Roller shade wiring diagram

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5. Include commissioning and verification in the specifications

Shading systems Daylighting controls

Field commissioning tools: Goal – meet specs before occupancy

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3. Function: How does it do it?

NYT site

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LBNL shade commissioning cart at The New York Times Headquarters Building

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Step-by-step How-to Guide

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Auto mode:

Overridemode:

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Pilot Demonstration

• Conference Room Setting in Washington DC (West-facing)

• 41x50-inch EC windows, SHGC=0.40-0.08, Tv=0.52-0.03, U=0.347 Btu/h-°F-ft2

• Electrochromic Window Controls:– On-off window tinting– Seasonal solar control when unoccupied (tinted

during summer, bleached during winter)– Lower windows tinted based on 20,000 lux threshold

vertical illuminance– Upper windows tinted based on 30,000 lux threshold– Manual override

• Lighting controls:– DALI dimmable ballasts– Architectural scenes, occupancy, daylight controls

• Monitoring underway

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New San Francisco Federal Building: A Naturally Ventilated Office Tower• Shallow plan for daylighting and cross-

flow ventilation• Open plan perimeter offices have no

mechanical cooling or ventilation• Exposed 8-inch ceiling slab acts as

thermal flywheel• Automatically-controlled windows provide

fresh air and night flush• Occupant-operated windows provide local

control • Work supported by the California Energy

Commission, the General Services Administration and the Federal Energy Management Program.

• Images courtesy of Morphosis and Arup

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Lawrence Berkeley National LaboratoryImages courtesy of Morphosis and Arup

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Images courtesy of Morphosis and Arup

Images courtesy of Morphosis and Arup

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Building controls virtual testbed (BCVTB)

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Control System Testing Using Design Simulations

• Test control system using design simulation:– Real-time EnergyPlus Hardware interface Control

hardware from the building– Does the control program produce the expected

performance?

Virtual Building Real Control SystemAlgorithmsHardwareA/D

D/A +

SPARK + EnergyPlus

EnergyPlus & SPARK

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All software modules reusable without code modification

Controls algorithm(MATLAB/Simulink)

Master Implementation (Ptolemy II)Real-time output (Ptolemy II)

Building temperatures and airflow(EnergyPlus)

Natural Ventilation in SF Fed. Bldg.

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Façade as HVAC + Lighting System

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http://lowenergyfacades.lbl.gov

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Conclusions

• High-performance facade solutions require a cross-disciplinary approach to address:

– Direct sun control– Glare control– Lighting quality– View– Daylight admission for lighting energy savings– Solar heat gain/ cooling load control for HVAC– Daylighting control system performance

• Industry is working toward more cost-effective solutions with features that address practical building owner and occupant needs

• Further work is needed to make these solutions routine, cost-effective, and reliable for all applications.

high performance building facade solutions · building facade solutions 2 lawrence berkeley...

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