A Window on the Future: Fenestration Fundamentals ... · Construction 34.1 Remodeling 17.2...

1

Windows MatterWindows Matter

(Plus: A Few Reminders About The Importance of Building

Energy Performance) Our Motto for the

Evening…

The End in MindThe End in Mind•The Worst Window…•Performance Beyond the Worst…•Why Windows Matter…

•The Energy Megatrend

Who Am I?Who Am I?– Building Scientist and Educator

• How Do Buildings Work?– Standards Writer on Building Performance

• How Do We Test Them?– Building Code Developer and Trainer

• How Do We Ensure Delivered Performance?

– A Beekeeper…• Learning from the ultimate building scientists…

Today We…Today We…

• Will Cover– Performance

Fundamentals– Glass Fundamentals– Thermal Performance– Some Building &

Window Modeling– Comfort Issues– Carbon Implications

• Won’t Cover– Dynamic Glazing– Material Distinctions– Non-Residential (though

the lessons are transferable)– Future Technologies

Efficient Windows?Efficient Windows?

2

Early Energy Code SolutionsEarly Energy Code Solutions How Do We Pick a Window?How Do We Pick a Window?• Aesthetics• Cost• Heat Loss• Heat Gain• Air Leakage• Water Penetration• Wind Load Resistance• Sound Transmission• Fabric Fading Potential• Condensation Resistance

• Visible Light Transmission

• Daylighting• Ventilation Efficiency• Operating Characteristics• Maintenance & Durability• Code Compliance• Warranty Considerations• Other Issues

Macro versus MicroMacro versus Micro• Macro Thinking

– Southeast– North Carolina– Asheville– “Energy Star Windows”

• Micro Thinking– North Asheville on a

site facing due west, overlooking a lake, near the highway, open to prevailing NW winds, primarily west and east-facing glass and a black-topped driveway to the south

– Best window for MY job

Macro ThinkingMacro Thinking

…a good place to START

…but, alone, often lead to least common denominator results.*

…can help avoid some of the more location-specific potential problems.*

Micro DecisionsMicro Decisions Microclimate is PersonalMicroclimate is Personal

• Comfort– Physical– Emotional– Safety– Environmental– Financial

3

Microclimate ConsiderationsMicroclimate Considerations• Temperatures

– Summer Peak– Winter Peak– Diurnal Swing

• Moisture– Rain, snow, sleet– Relative Humidity– Condensation

• Wind– Peak Gusts– Sustained Gusts

• Radiation– Heat Gain– Heat Loss

• Relative Humidity– Ventilation

considerations• Local Pollutants

– Smog, Acid rain– Sand, dust– Highway or industrial

particulates– Noise

More Microclimate IssuesMore Microclimate Issues• Security (climate?)

– Human– Animal– Wind-borne debris

• Seasonal Climate issues– Monsoons– Hurricanes– Tornadoes– Blizzards– Locusts

• Movement– Earthquakes– Settling/expansive

Soils– Wind

• View(s)– Orientations– Reflections

• Privacy– Proximity

• Other

Microclimate WaterMicroclimate Water• Rain• Rain Direction• Lakes, Streams• Snow• Steam• Sleet• Fog

Privacy is a microclimate consideration

More microclimate concernsMore microclimate concerns• View• Scenery• Nature• Beauty• Privacy

Protection from Wild AnimalsProtection from Wild Animals

4

More “Micro” ConsiderationsMore “Micro” Considerations•Component Performance

– Glass Performance (IGs, laminates, coatings)– Frame Performance (Monolithic or

composites)– Hardware Performance (Operators, locks,

balances, etc.)• Integration (on-site)

– Water management, security, etc.

But first, we have to meet the requirements of the

The Building Code!

What is the Code?What is the Code?•Least safe…•Least strong…•Least energy efficient…

…building allowed by law.

We’re not allowed to build it any crappier…

Disaster Breeds CodesDisaster Breeds Codes

Disaster Breeds Codes…Disaster Breeds Codes…•Code of Hammurabi – 1750 BC

– One of the first “Building Codes”– “Failure” put the builder’s life and property

at risk

•Let’s get a quick refresher in what ol’ Ham had to say…

Code of Hammurabi <snip>Code of Hammurabi <snip>• 229: If a builder has built a house for a man and

his work is not strong, and if the house he has built falls in an kills the householder, that builder shall be slain.

• 232: If goods have been destroyed, he shall replace all that has been destroyed; and because the house was not made strong, and it has fallen in, he shall restore the fallen house of his own material.

• 233: If a builder has built a house for a man, and his work is not done properly and a wall shifts, then that builder shall make that wall good with his own silver.

5

Disaster Breeds Codes…Disaster Breeds Codes…•The Burning of Rome – 64 AD

– Nero didn’t like the slums and stench– Established fire safety and sanitation

requirements for all buildings following the fire

Europe Learns…Europe Learns…•The Great London Fire – 1666 AD

– Black Plague, raw sewage, tightly spaced buildings…

– Two-thirds of the city destroyed– “London Building Act” adopted after the fire

US Code Milestones…US Code Milestones…•The Chicago Fire – 1871 AD

– Mrs. O’Leary’s cow…– Destroyed 17,000 buildings, killed 250

people, left 100,000 homeless. – Bankrupted the insurance industry – New code adopted in 1875 regulating

building construction and fire prevention.

More US Code MilestonesMore US Code Milestones•The San Francisco Earthquake –

1906 AD– What the earthquake didn’t get, the fire did– One of the major influencers of today’s

structural, fire and life safety codes

First Energy Code MilestoneFirst Energy Code Milestone•Arab Oil Embargo – 1973-4

– President Carter’s Fireside Chat (“Turn your thermostat down to 65 and wear a sweater”and “Drive 55”)

– Precipitated the first energy codes for buildings – ASHRAE 1975

Hurricane AndrewAugust, 1992175 mph wind gusts$25 billion damage

6

Recent Code MilestonesRecent Code Milestones•Hurricane Andrew – 1992 AD

– 90% of all homes in Dade County Florida had roof damage

– 117,000 homes were destroyed or had major damage

– Primary driver of today’s hurricane protection codes

More Recently…More Recently…

Katrina’s Legacy…Katrina’s Legacy…•Hurricane Katrina – 2005 AD

– Costliest hurricane in history – est. $80 billion

– Over 1300 confirmed deaths– 3200 still missing

•Louisiana and Mississippi? – Just considering their first Building Code!

Disaster TeachesDisaster Teaches

I-35W Bridge Construction in 1967

We Wait for DisasterWe Wait for Disaster•History has shown that we WAIT for

disaster, THEN we react.

There are consequences to waiting…

Sea Level +1M

New Orleans

Lake CharlesBeaumont

Baton Rouge

Weiss and Overpeck, University of Arizona

What if we wait for sea level to rise 1 meter

7

Sea Level + 6MMiamiFt. Lauderdale

Daytona Beach

Jacksonville

St. Petersburg

Fort Meyers

Panama City

Weiss and Overpeck, University of Arizona

What if we wait for sea level to rise 6 meters? What About Energy Codes?What About Energy Codes?•“Disaster” is not as easy to define

•“Pain” is relative– $3 per gallon gasoline? $6? $10?– $0.15 per kWh electricity? $0.25? $0.50?– $50 per barrel of oil? $75? $100?

Another kind of pain…

Before we go too deeply into the specifics about window performance…

“Understanding the Size of Things…”

Buildings & EnergyBuildings & Energy

Source: EIA 2007

Buildings > 40%

Transportation28%

Industrial32%

8

The Size of Things…The Size of Things…• There are over 110 million existing

residential buildings – (From US census data)

• ~64% of all windows are Single Pane – Replacement assumed at 14 per home– (Source: USDOE Core Data Book)

• Using “Chris Math” this means that we have about 1 Billion single pane windows that need to be replaced!

Fixing the “Problem”Fixing the “Problem”•1 Billion Single Pane Windows in

Existing Homes•We install about 35 million windows

in replacement per year– Half of these are clear glass!

• It will take 40 to 60 years to replace these energy hogs (old and new) with energy efficient ones

This assumes that we INCREASE the rate of market penetration of GOOD Windows!

Window Market SegmentationWindow Market Segmentation

Remodeling New

Replacement

Source: Ducker Research 20060

5

10

15

20

25

30

35

40M

illio

n U

nits

.

New Construction

34.1

Remodeling 17.2

Replacement 19.2

Manufactured Housing

1.8

Residential Window Sales - 200572.3 Million Units

The “Problem” Continues…The “Problem” Continues…•48% of today’s window sales have

clear glass – (Source: Ducker Research 2006)

•Over 35 million residential windows each year are produced without good glazing!– New and Replacement

Frame TypesFrame Types

Wood 19.2Vinyl 40.6

Aluminum 8.7

Other 1.9


9

Commercial 463MM

Residential 1,339MM

Glazing by Construction TypeGlazing by Construction Type

Total: 1,803 Million Square Feet


Residential Glass TypesResidential Glass Types

Low-E56%

Non-Low-E44%


Commercial Is Even WorseCommercial Is Even Worse

Low-E37%

Non-Low-E63%


Every Project Is DifferentEvery Project Is Different

• Design Loads are Project Specific

• Wind Loads are Project specific

• Exposures are Project specific

Longaberger Basket Corporate HeadquartersNewark, OH

Now, let’s talk about Windows and Energy

Old (Wrong) “Rules of Thumb”Old (Wrong) “Rules of Thumb”•Windows are Bad

– Too much heat loss– Too much heat gain– They leak (air, water,

heat)•Skylights are Bad

– Same reasons– Overhead!

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More Old Wrong “Rules”More Old Wrong “Rules”•Glass performance = Window

performance•To save the most energy, minimize

window area•Only four glass options available

– Single, Double, Tint, Low-e•Low-e = Energy Efficient•All Low-e glazings are the same

Old Window Material “Rules”Old Window Material “Rules”•“Wood is good”•“Vinyl is new”•“Steel is safe”•“Aluminum is strong”•“That’s all the options you get….”

Today, over 50% of the windows sold are of some type of

composite material or composite construction...

Specification ChallengesSpecification Challenges• Can no longer just specify “wood

windows” or “aluminum” or “vinyl”• Sometimes two, three even as many as

20 different materials may make up a window

• All of these materials perform differently

Yet PERFORMANCE is what you are really seeking in

specification and product selection...

Old Performance “Rules”Old Performance “Rules”•“Performance Values are Reliable”•“Higher R-values are better”•“Windows Don’t Leak”•Glass Seals Will Last “A Long Time”

(Translation: “Forever”)•“Not Much More Area for

Performance Improvement….”

Energy Performance BasicsEnergy Performance Basics•U-factor•Solar Heat Gain Coefficient•Visible Transmittance•Air Leakage

But before we go TOO far...

Chris’s Rule # 1Chris’s Rule # 1

“Compare WHOLE PRODUCTWHOLE PRODUCTPerformance Values”

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Comparing PerformanceComparing Performance

?Whole Product vs. Center of Glass PerformanceWhole Product vs. Center of Glass Performance Frame area

Edge-of-glass area

Center-of-glass area

Different Materials:•Wood•Vinyl•Aluminum•Glass•Steel•Sealants•Gases•Laminates•Coatings•etc.

Specification Basics: EnergySpecification Basics: Energy•U-factor•Solar Heat Gain

Coefficient•Visible

Transmittance•Air Leakage

•Project specific•High rise? Low-rise?•Residential? Industrial?•Office? School?

•Climate specific•Hot? Cold? Mixed?•Dry? Humid?•Sandy? Snowy?•Altitude?

•Microclimate specific•Orientation•End Use

Methods of Heat TransferMethods of Heat Transfer

1. Conduction (∝ ti – to)

2. Convection (∝ ti - to )

3. Radiation (∝ t14 - t2

4 )

First, let’s talk about heat loss...

12

ConductionConductionHeat transfer

through materialscaused by atemperaturedifference

70°FRoom Temp.

0°FAir Temp.

5°F

68°F

Qcond∝ Δt Heat transferdue to airmovement

70°FRoom Temp.

0°FAir Temp.

Qconv∝ Δt

ConvectionConvection

Heat transfer betweensurfaces of differenttemperatures.

70°FRoom Temp.

ColderSurfaces

RadiationRadiation

Qrad∝ t14 - t2

4

Windows Windows exhibit each exhibit each type of heat type of heat transfer transfer ––both summer both summer and winter!and winter! Convection –

inside, outside and between the glass

Wintertime Heat Loss

Conduction –through the frame, spacer, and glass

Radiation –direct, re-radiated, inside, outside and between the glass

Heat Loss in WinterHeat Loss in Winter

0°F 70°F

Heat Loss & WindowsHeat Loss & Windows

0

0.3

0.6

0.9

1.2

1.5

U-Factors

Existing New

• Common aluminum-framed, single glazed windows lose 3 to 4 times more heat in winter than today’s most basic energy efficient technologies

• Cold glass surfaces with recurring condensation

• BIG impact on comfort• BIG impact on heating

costs

13

“U-Factor”“U-Factor”• Amount of heat transmitted through the

window due to a temperature difference between inside and out.– Includes Conduction, Convection and Radiation heat

transfer through the unit• The lower the value, the less heat is lost

through the window in the winter• Simple Rule for heating climates:

– Look for products with a U-factor < 0.35

Now, let’s talk about heat gain...

Of course, there are many types of solar control...

Solar Control Fundamentals…Solar Control Fundamentals…

More Solar Control...More Solar Control... Add-on Solar Control…Add-on Solar Control…

14

A Southern Art Form…A Southern Art Form…LengthSummer

sunWinter

sun

Height

Solar Heat GainSolar Heat GainDiffuseradiation

DirectradiationReflected

radiation

Windows Windows exhibit each exhibit each type of heat type of heat transfer transfer ––both summer both summer and winter!and winter! Convection –

inside, outside and between the glass

Summertime Heat Gain

Conduction –through the frame, spacer, and glass

Radiation –direct, re-radiated, inside, outside and between the glass

Heat Gain & WindowsHeat Gain & Windows

0

0.2

0.4

0.6

0.8

1Solar Heat Gain

Existing New

• Air conditioning energy is very expensive

• New window technologies are over three times more efficient at blocking unwanted heat gain than common aluminum-framed, single glazed windows

• Windows generally drive the air conditioning load (residential)

• Windows generally determine the perimeter load (commercial)

15

Homes Have ChangedHomes Have Changed

49%

91%

40%

50%

60%

70%

80%

90%

100%

1973 2005

New Single Family Homes with Air Conditioning

Window solar gain is the single largest contributor to cooling loads

Source: US Census 2005

“Solar Heat Gain Coefficient”“Solar Heat Gain Coefficient”•The fraction of the incident solar

radiation (at direct normal incidence) that is actually transmitted through the window in the form of heat

•The lower the value, the less heat gain into the space

•Simple rule for cooling climates:– Look for SHGC values <0.35

Well, what if I just specify “low-e windows”? Isn’t

that good enough?

NO!Different low-e glazings perform differently!

Spectral SelectivitySpectral Selectivity

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5

Wavelength (microns)

Tran

smitt

ance

(%)

ClearGray / BronzeHigh Transmittance Low-ESpectraly selective tint and Low-ESpectrally selective Low-E

IRUV VIS

What Flavor is Your Glass?What Flavor is Your Glass?

0%

10%

20%

30%

40%

50%

60%

70%

80%

300

380

780

2500

UV Visible Near Infrared

Clear HSLE1 HSLE2 MSLE LSLE1 LSLE2

Tran

smis

sion

%

Dee’s Door Shows ThisDee’s Door Shows This

16

Visible TransmittanceVisible Transmittance•How much of the VISIBLE portion of

the solar spectrum is transmitted•The higher the value, the more

“clear” the window appears•Simple Rule:

– Look for Tvis values greater than 0.50

Then, of course, there is air leakage...

WINDWIND

““Air LeakageAir Leakage””Window Type, Placement and Partitions Impact Ventilation

Window air leakage is NOTNOT a good ventilation strategy!

Pollutant Control?Pollutant Control? “Air Leakage”“Air Leakage”• A measure of a window’s air tightness

under a fixed set of laboratory conditions– Currently at constant temperature and pressure,

may evolve to testing at differential temperatures• The lower the value, the tighter the

window– Tradeoffs may occur between tightness and ease of

operations• Simple rule:

– Look for air leakage less than 0.20 cfm/sq.ft.

17

Recap of Rule #1Recap of Rule #1•Specify and Compare Whole Product

Performance Values•Chris’s Simple Specification Rules:

– U-factor < 0.35– SHGC < 0.35– Visible Transmission > 0.50– Air Leakage < 0.20

All Buildings Are Similar?All Buildings Are Similar?

A Brief History Lesson

How Did We Get Here?How Did We Get Here?•1973 Revisited

– Automobile Efficiency, Industrial Efficiency and Building Efficiency

•Solutions– EPA MPG’s, Appliance Standards, Utility Rate

Increases– More Insulation

• New Construction Standards• Weatherization Programs for Existing Construction

Rating CertificationRating Certification

R30InsulationInsulation

AutomotiveAutomotive

28 City30 Highway

Your actual mileage may vary dependingon driving conditions and other factors

1998 ToyotaCorrolaSedan4 Speed2L Engine

AppliancesAppliancesA Means of Comparison…

What About the Windows?What About the Windows?•Big Energy Losers

– Especially after insulated walls and attics•Limited Solutions

– “Double Pane”, Storm Windows, Tinted Glass•No Reliable Energy Performance

Ratings– Outrageous and illegal performance claims

•Code “Solutions” = Less Windows– Most approaches “traded out” windows

18

Window Industry Responds...Window Industry Responds...•Innovation

– Low-e glazings– Gas filled IG units– Low conductivity spacers– New frame designs– Variety of new glazing transmission

properties

But a lot of these innovations are INVISIBLE!

Well, what if I just specify “low-e windows”? Isn’t

that good enough?

NO!Different low-e glazings perform differently!

Two “Low-E” WindowsTwo “Low-E” Windows

Message: They may LOOK the same - but can perform very differently.

Two Solar Control OptionsTwo Solar Control Options

Message: They may LOOK different - but can perform the same!


DonDon’’t Trust Your Eyes!t Trust Your Eyes!––Can look the same, but Can look the same, but perform differently;perform differently;

––Can look different, but Can look different, but perform the same.perform the same.

Tinted

Clear

Color

0.2540%LSLE20.2766%LSLE10.4172%MSLE0.6378%HSLE20.7175%HSLE10.7882%Clear

SHGCVisible Light

New Style GlassNew Style Glass

Don't trust your eyes - read the label!

19

Low-E LocationLow-E Location

On surface 2:• reduces solar

gain• roomside glass is

cool

On surface 3• absorbed sunlight

goes into room• HOT glass! Inside Glass Temperatures –

Winter DayInside Glass Temperatures –Winter Day

MSLE HSLE Clear

Frame, Edges and Seals?Frame, Edges and Seals? Window Industry Responds...Window Industry Responds...•Reliable Energy Ratings

– State-of-the-art Testing and Evaluation– Third Party Certification Authorization– Working with builders, architects and

regulators– Like MPG’s, R-values and Energy Guide

Labels•New Code Solutions

Window Energy Ratings?Window Energy Ratings?•National Fenestration Rating Council

(NFRC)•Formed in 1989 to provide a fair,

accurate and credible energy rating and labeling system for windows, doors and skylights

•Coordinates certification and labeling of energy performance

•Certified Energy Ratings

NFRC LabelNFRC Label• Certified Energy

Performance– U-factor– SHGC– Tvis– Air Leakage

20

AdvantagesAdvantages•Instant, Accurate, Directly

Comparable Energy Ratings•Rating Applies to all Types of

Products•Eliminates Confusion Deciphering

Manufacturer’s Literature•Demonstrates Compliance to Local

Codes•Accurate HVAC System Sizing

Why is Certification Important?Why is Certification Important?

•Independently-determined ratings•Checked and verified by an

independent, third party•Assurance of “getting what you pay

for”•Manufacturer’s commitment to its

customers•Code Compliance


“Don’t Trust Your Eyes”leads to.....


“Require Performance Certification

and Labeling.”

If It’s Not Labeled… ?If It’s Not Labeled… ?•Does it have…

– Low-E coatings? • Which one?

– Gas fills? Which one?– Low-conductivity

spacers?•Does it meet…

– Local codes?– Performance

expectations?– Comfort expectations?

Chris’s RulesChris’s Rules•Compare Whole Product

Performance– Not center of glass

•Don’t Trust Your Eyes– Can look the same but perform differently– Can look different but perform the same

•Require Performance Certification and Labeling

21

Safety Glazing 101Safety Glazing 101•Glass breaks•It can hurt you•It can hurt others•The code attempts to regulate that•Hollywood ignores these regulations

for dramatic effect…

“Ghost” Sequence“Ghost” Sequence Types of Safety GlazingTypes of Safety Glazing•Laminated Glass•Tempered Glass•Safety Insulating Unit•Others

– Plastic Glazing– Organic-Coated Glass– Wired Glass

Laminated GlassLaminated Glass

• Glass Retention• Qualifies as Safety Glass• Increased Burglar Resistance• Increased Impact Resistance• Improved Sound Control (STC)

Glass

Glass

Plastic Interlayer

Single LiteForced EntryBomb BlastHurricaneAcoustical

Safety

Laminated InsulatedSame as Single Plus:Energy ConservationEnhanced Acoustical

- Can be Double Laminated

Multiply LaminatedSame as Single Plus:

Enhanced Forced EntryBullet Resistance

Enhanced Blast Resistance

Laminate ConfigurationsLaminate Configurations

22

Laminate ExamplesLaminate Examples

Monolithic Impact Resistant Glazing

Insulating Impact Resistant Glazing

Different NeedsDifferent Needs•Some jobs may need additional

– Safety performance• Like your car windshield

– Security performance• Resistant to intrusion

– Sound performance• Quiet

Bag TesterBag Tester SG Specialty ApplicationsSG Specialty Applications•Hurricane•Bomb Blast•Earthquake

Safety Glazing RealitySafety Glazing Reality•Three photos of an important

moment in safety glazing history

23

So… Let’s Design a WindowSo… Let’s Design a Window•What Forces?•How to Best Meet Those Forces?•Priorities?

•Class Participation

Unit Size

Importance factorExposure

Wind Speed

Location in Wall

Mean Roof Height

MRH

Six basic elements are used to calculate design pressure requirements:

Design Pressure ElementsDesign Pressure Elements

Coastal Design Example…Coastal Design Example…•One in seven Americans live along

the Atlantic and Gulf coasts•140 coastal counties make up 52%

of the U.S. housing supply•Over 1500 residential building

permits are issued every day in coastal counties

Why Does This Matter?

24

Hurricanes and Housing…Hurricanes and Housing…•Hurricane Andrew caused over $30

billion in insured loses•New York ranks 2nd in

cost/disasters – Florida ranks 1st.• Insurers forced to suspend or

terminate underwriting activity in certain areas of the state.

Still Closer…

Opening Protection?Opening Protection?•To protect against wind-borne

debris in high wind areas•Testing and certification required

– Yes, we get to break things…– Only this time we use a cannon…– And we load it with lumber…

No, this is not a joke…

Loading the CannonLoading the Cannon

Annealed GlassAnnealed Glass Laminated GlazingLaminated Glazing

25

Pressure CyclingPressure Cycling Not Just a Coastal Issue…Not Just a Coastal Issue…

The Need for StandardsThe Need for Standards

Historical Perspective…Historical Perspective…

Past as PrecedentPast as Precedent1975 1985

Arab Oil Embargo - 1973

ASHRAE 1975 -Restricts Window Area

Energy Policy Act of 1992References NFRC

MEC 1995 – Introduced First Prescriptive Window Requirements

Model Energy Code (circa 1985)HDD Driven, Windows Part of Wall

1995

What Actions Did We Take?What Actions Did We Take?•Tried to Save Energy

– Developed Standards• Buildings, Cars, Appliances, Industrial Processes

– Innovated (new technologies)– Adopted Minimums (codes)– Provided Incentives

• Utility Programs, etc.

26

Why Standards?

AppliancesAppliances

A Means of Comparison…

AutomotiveAutomotive

How Far Can We Go?How Far Can We Go?

Recap: What is the Code?Recap: What is the Code?•Least safe…•Least strong…•Least energy efficient…



Total Window U-factor requires knowledge of glass andframe properties.

27

Many Low-E CoatingsMany Low-E Coatings

0.250.04

0.240.02

0.260.08

0.310.20

0.48Uncoated (0.84)

Emittance Double Pane Glass U-Factor

The Rule of PanesThe Rule of Panes

Every Layer of Glass

in a Multi-Pane Unit

Equates to

1 Point

in

R-Value

U & Temperature vs. No. of PanesU & Temperature vs. No. of Panes

0.10

0.20

0.30

0.40

0.500.60

0.70

0.80

0.90

1.00

1 2 3 4 5 6 7 8Number of Panes

25

30

35

40

4550

55

60

65

70

Roo

msi

de G

lass

Tem

pera

ture

U-Factor 0F Outdoor

Cen

ter o

f Gla

ss U

-Fac

tor

Air Space Heat TransferAir Space Heat Transfer

RADIATION– 2/3 of heat transfer– blocked with “low-E” coatings

Conduction/Convection– 1/3 of heat transfer– retarded with gas fill (argon)

Air Space Heat TransferAir Space Heat Transfer

2

2

22

21

16

19

10

13

0 5 10 15 20 25 30 35

Low-E, ArgonFilled

Low-E, Air Filled

Clear Glass,Argon Filled

Clear Glass, AirFilled

Btu/hr/ft2 @ 70° F ΔT

RadiationConduction

New Glass MathNew Glass MathGlass Type Approximate R-Value

1st layer of glass 1

2nd layer of glass 1

Low-Emissivity coating 1

Argon Gas fill 1

Total 4Quad pane performance with double glazing!

28

Advanced Glass MathAdvanced Glass Math

0.100.200.300.400.500.600.700.800.901.00

Single Pane

Double Pane

Triple Pane

Doublew/LoĒ &argon

Triplew/1 LoĒ& argon

Triplew/2 LoĒ& argon

25303540455055606570

Roo

msi

de G

lass

Tem

p

U-Factor 0F Outdoor

Cen

ter o

f Gla

ss U

-Fac

tor

What About 2 Low-E Coatings?What About 2 Low-E Coatings?

.25Low-E (0.04)Uncoated

.25UncoatedLow-E (0.04)

.28Mid-E (0.20)Mid-E (0.20)

.31Mid-E (0.20)Uncoated

32Glass

U-FactorSurface #

1 2 3 4

U vs. Gap Width & EmittanceU vs. Gap Width & Emittance

0.100.150.200.250.300.350.400.450.500.55

1/4"(6.5mm)

3/8"(9.8mm)

1/2"(13.0mm)

5/8"(16.0mm)

3/4"(19.5mm)

Airspace Gap Width

Clear Double Mid-E (0.20) Low-E (0.04)

Cen

ter o

f Gla

ss U

-Fac

tor

U-Factor Air vs. ArgonU-Factor Air vs. Argon

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

1/4" (6.5mm) 3/8" (9.8mm) 1/2" (13.0mm) 5/8" (16.0mm) 3/4" (19.5mm)Gap Width

Mid-E Air Mid-E Argon Low-E Air Low-E Argon

Cen

ter o

f Gla

ss U

-Fac

tor

U-Factor Argon vs. KryptonU-Factor Argon vs. Krypton

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

1/4" (6.5mm) 3/8" (9.8mm) 1/2" (13.0mm) 5/8" (16.0mm) 3/4" (19.5mm)

Gap Width

2P LE + Argon 2P LE + Kyrpton 3P (2)LE + Argon 3P (2)LE + Kyrpton

Cen

ter o

f Gla

ss U

-Fac

tor

U-Factor vs. Gas FillU-Factor vs. Gas Fill

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Argon Fill Level

Clear Double Mid-E (0.20) Low-E (0.04)

Cen

ter o

f Gla

ss U

-Fac

tor

29

Translating Glass Performance Into Window

Performance...

Understanding U-factor Limits

Translating Glass Performance Into Window

Performance...

Understanding U-factor Limits

Table 4 Close-upTable 4 Close-up

Source: ASHRAE Handbook of Fundamentals

Scatter Plot of Table 4Scatter Plot of Table 4

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

0.10 0.20 0.30 0.40 0.50Glass U-Factor

Aluminum Aluminum TB Clad Wood Wood / Vinyl Ins Vinyl

Linear (Aluminum) Linear (Aluminum TB) Linear (Clad Wood) Linear (Wood / Vinyl) Linear (Ins Vinyl)

Who

le W

indo

w U

-Fac

tor

Operable WindowOperable Window

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

0.10 0.20 0.30 0.40 0.50

Glass U-Factor

Aluminum Alum TB CladWood Wood or Vinyl Insulated

Who

le W

indo

w U

-Fac

tor

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.10 0.20 0.30 0.40 0.50Glass U-Factor

Aluminum Alum TB CladWood W/V (1995) Improved W/V Insulated

Updated Operable WindowUpdated Operable Window

R4R8

Who

le W

indo

w U

-Fac

tor

R2

30

Total Window SHGC requires knowledge of glass propertiesandframe area.

50%

60%

70%

80%

90%

1 2 3 4 5 6 7 8Number of Clear Glass Panes

0.50

0.60

0.70

0.80

0.90

Layers Reduce Transmission!Layers Reduce Transmission!

Visi

ble

Tran

smis

sion

%

Solar Heat G

ain Coefficient

“Un-obtanium”

0.5048%0.6362%Tint

0.2218%------Reflective

0.7280%0.7882%Clear

SHGCVisibleSHGCVisible

6 mm Glass3 mm Glass

Old Style GlassOld Style Glass

What you see is what you get!

What Flavor is Your Glass?What Flavor is Your Glass?

0%

10%

20%

30%

40%

50%

60%

70%

80%

300

380

780

2500

UV Visible Near Infrared

Clear HSLE1 HSLE2 MSLE LSLE1 LSLE2

Tran

smis

sion

%

They look different - but have the same solar gain!They look different - but have the same solar gain!

Tinted

Clear

Color

0.2540%LSLE20.2766%LSLE10.4172%MSLE0.6378%HSLE20.7175%HSLE10.7882%Clear

SHGCVisible Light

New Style GlassNew Style Glass

Don't trust your eyes - read the label!

31

Low-E LocationLow-E Location

On surface 2:• reduces solar

gain• roomside glass is

cool

On surface 3• absorbed sunlight

goes into room• HOT glass! Inside Glass Temperatures –

Winter DayInside Glass Temperatures –Winter Day

MSLE HSLE Clear

More on Translating Glass Performance

into Window Performance...

Understanding Solar Heat Gain Limits

More on Translating Glass Performance

into Window Performance...

Understanding Solar Heat Gain Limits

Frame Area is the DriverFrame Area is the Driver

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80

Glass SHGC

Alum, Fixed Alum, Operable W/V, Fixed W/V, Operable

Frame AreaAL Fixed =12%AL Operable=15%Wood/Vinyl Fixed =15%W/V Operable=25%

Win

dow

SH

GC

32

NFRC Certification

U-Factor

SHGC

Certified Energy Performance Certified Energy Performance

Windows&

Air Conditioner Sizing(if we have time)

Windows&

Air Conditioner Sizing(if we have time)

Air Conditioner and Heat Pump

Sizing Chart

Instructions:1. Stand at the curb and look at the house through cut outs. 2. Pick the hole that best fits the house.3. Choose the unit size shown at the bottom of that cutout.

Trim out on dotted lines carefully. Then follow instructions below.

1½ to 2 tons

2½ to 3½tons

4 to 5 tons

(cut out)(cut out)

(cut out)

Another Visual Sizing MethodAnother Visual Sizing Method

Complex Sizing MethodComplex Sizing Method

300+ pagesof

tabular data!

The "Window" PerspectiveThe "Window" Perspective

Solar GainThe “Other Stuff”

33

"Other Stuff" Expanded "Other Stuff" Expanded

•Heat Gain– Roof and Walls: U*A*ΔT– Infiltration– Internal Gains– Latent Gains

•Distribution System Efficiency– Duct Leakage– Thermal Gains

U * A * ΔTU * A * ΔT

•Get U-Factor from climate zone

•Area is simple math– Length, Width, Height– Stories

•Delta T is location dependent– Use climate zone "average"

IECC Climate

Zone

Window U Wall R Ceiling R

7-8 0.35 21 496 0.35 19 495 0.35 19 384 0.40 13 383 0.65 13 302 0.75 13 301 1.20 13 30

Single Story House UASingle Story House UA

0

100

200

300

400

500

600

700

800

900

1,000

2,000 2,500 3,000 3,500 4,000

Conditioned Floor Area, ft2

UA

CZ2 CZ3 CZ4 CZ5 CZ6

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

110

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Heating Degree Days (HDD65)

Des

ign

Tem

pera

ture

, °F

Temperature SimplificationTemperature Simplification

Heating

Cooling

IECC Climate

Zone

Heating Design

(°F)

Cooling Design

(°F)

7-8 -24 886 -14 905 -2 924 8 943 20 962 27 971 36 99

34

Envelope Heat GainEnvelope Heat Gain

0.0

0.5

1.0

1.5

2.0

2.5

2,000 2,500 3,000 3,500 4,000

Conditioned Floor Area, ft2

Tons

CZ2:1-Story CZ2: 2 Story CZ6: 1-Story CZ6: 2-Story

CoolingLoadFactors from MJ8CoolingLoadFactors from MJ8

28° 34° 40° 46°North 37 37 35 34NE 149 140 135 130East 220 219 216 213SE 172 185 196 205South 91 121 149 173SW 172 185 196 205West 220 219 216 213NW 149 140 135 130

Latitude

CLF by Orientation & LatitudeCLF by Orientation & Latitude

0

50

100

150

200

250

North East/West South

Coo

ling

Load

Fac

tor

28° 34° 40° 46°

CLF for "Typical" DistributionCLF for "Typical" Distribution

0

50

100

150

200

250

West Back South Back

Ave

rage

CLF

28° 34° 40° 46°

Understanding Design TempsUnderstanding Design Temps

y = -0.01x + 40.12

y = -0.001x + 99.870

-40

-20

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

HDD

Des

ign

Tem

p,

Common Design TemperaturesCommon Design Temperatures

88F12FBoston91F24FNorfolk92F23FAtlanta92F40FOrlando

Cooling Design Temperature

Heating Design Temperature

East Coast Cities – I-95

Range: 28F vs. 4F

35

More Design TemperaturesMore Design Temperatures

88F-10FMinneapolis94F7FKansas City98F22FDallas96F30FSan Antonio



Central Cities –I-35

Range: 40F vs. 10F

More Design Temperatures-2More Design Temperatures-2

87F27FPortland101F33FFresno

89F7FSpokane95F12FSalt Lake City

106F32FLas Vegas108F40FPhoenix



West Coast Cities

Range: 33F vs. 19F

Heating and Cooling Design TsHeating and Cooling Design Ts

-40

-20

0

20

40

60

80

100

120

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

HDD

Des

ign

Tem

p, °F

IECC Climate

Zone

Heating Design

(°F)

Cooling Design

(°F)

7-8 -24 886 -14 905 -2 924 8 943 20 962 27 971 36 99

Remember? Homes Have ChangedRemember? Homes Have Changed

49%

91%

40%

50%

60%

70%

80%

90%

100%

1973 2005




Peak Cooling for Clear GlassPeak Cooling for Clear Glass

Duct Losses

Heat Gain

Solar Gain

36

Peak Loads - 2000 ft2 HousePeak Loads - 2000 ft2 House

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.70 0.60 0.50 0.40 0.30 0.20 0.10

Clear HSLE Tinted Code MSLE LSLE Reflective

Window SHGC

Tons

DuctLossSolarGainHeatGain

Peak Loads by House SizePeak Loads by House Size

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0.70 0.60 0.50 0.40 0.30 0.20 0.10

Clear HSLE Tinted Code MSLE LSLE Reflective

Window SHGC

Tons

4,000 ft² 2,000 ft²

What's a Ton of AC Worth?What's a Ton of AC Worth?•Saving 1 ton of AC per house

– 1 ton = 12,000 Btu/hr– 13 SEER = 13,000 Btu/kWh– Using “Chris Math” – ~1 kW per house– 110 million existing homes, assume about

half have AC– ~50 million X 1 kW = 50 million kW

Roughly equal to about 100 new 500 MW coal-fired power plants…

Windows&

Comfort

(If we have time)

Windows&

Comfort

(If we have time)

Comfort = How We FeelComfort = How We Feel• Windows play a key

role in how we FEEL in a room– Too Warm?– Too Cold?

Comfort is a well understood science – and it is MEASUREABLE!

ASHRAE Standard 55

37

Comfort ReferencesComfort References Predicted Mean VotePredicted Mean Vote

The PMV model was developed by Fanger in the 1970s and is the standard method used to evaluate comfort in buildings.

7 Point Comfort Scale7 Point Comfort Scale

WarmCool

+1 +2 +3

Cold CoolSlightly

NeutralSlightly

Warm Hot

-3 -2 -1 0

PMV CalculationPMV Calculation

M = Metabolic rateL = thermal load on body

Predicted Percent DissatisfiedPredicted Percent Dissatisfied ASHRAE Comfort ProgramASHRAE Comfort Program

38

Comfort at the ThermostatComfort at the Thermostat

0%

5%

10%

15%

20%

25%

30%

35%

66°F 67°F 68°F 69°F 70°F 71°F 72°F 73°F 74°F

Thermostat Setting

Pred

icte

d Pe

rcen

t Dis

satis

fied

Window Specific InputsWindow Specific Inputs

Winter•Mean Radiant Temperature

– Window surface temperature– Window size– Proximity

Summer•Solar Impact

– Direct beam radiation– Absorbed & re-radiated (hot glass)

Glass and ComfortGlass and Comfort•A key determinant of room comfort

– Is the surface hot in the summer?– Cold in the winter?

•Good glazing can improve your comfort and save energy– Can sit and work closer to the windows– Access to natural light– May even impact thermostat settings

Efficient Windows CollaborativeEfficient Windows Collaborative

Winter ComfortWinter Comfort

0

10

20

30

40

50

60

70InsulatedWallLSLE

HSLE

Triple

Double

Single

Roo

m-S

ide

Surf

ace

Tem

pera

ture

(0F

outs

ide)

0%

10%

20%

30%

40%

Operable PatioDoor WindowWall

Pred

icte

d Pe

rcen

t Dis

satis

fied

Comfort with 52°GlassComfort with 52°Glass

25%

39

Comfort vs. Window SizeLow-E Double Pane, 70°F Thermostat, 3’ AwayComfort vs. Window SizeLow-E Double Pane, 70°F Thermostat, 3’ Away

10%

15%

20%

25%

30%

35%

40%

50 40 30 20 10 0

Outdoor Temperature, °F

Pred

icte

d Pe

rcen

t Dis

satis

fied

WindowWallPatioDoorOperable

Response to Winter ConditionsResponse to Winter Conditions

10

20

30

40

50

60

70

50 40 30 20 10 0Outdoor Temperature, °F

Roo

msi

de S

urfa

ce T

empe

ratu

re, °

F

WallQuad PaneDouble PaneSingle Pane

Comfort vs. ProximityLow-E Double Pane, 70°F Thermostat, Patio DoorComfort vs. ProximityLow-E Double Pane, 70°F Thermostat, Patio Door

10%

15%

20%

25%

30%

35%

40%

50 40 30 20 10 0


Pred

icte

d Pe

rcen

t Dis

satis

fied 2' away

3' away4' away

Comfort vs. Glass TypePatio Door, 70°F Thermostat, 3' AwayComfort vs. Glass TypePatio Door, 70°F Thermostat, 3' Away

10%

15%

20%

25%

30%

35%

40%

50 40 30 20 10 0


Pred

icte

d Pe

rcen

t Dis

satis

fied

Clear DoubleLow-E DoubleLow-E Triple

MRT SummaryMRT Summary

10%

20%

30%

40%

50%

Small Big Away Close Low-E ClearGlass

72°F 68°F

Window Size Proximity Glass Type Thermostat Setting

Pred

icte

d Pe

rcen

t Dis

satis

fied

Depth of DiscomfortPatio Door, 70°F ThermostatDepth of DiscomfortPatio Door, 70°F Thermostat

0

1

2

3

4

5

6

7

50°F 40°F 30°F 20°F 10°F 0°F

Outdoor Temperature

Dis

tanc

e A

way

(ft)

for 2

5% P

PD

Clear DoubleLow-E Double

40

Heating Thermostat OffsetPatio Door, 3' away, 25% max PPDHeating Thermostat OffsetPatio Door, 3' away, 25% max PPD

68

69

70

71

72

73

74

75

50°F 40°F 30°F 20°F 10°F 0°F

Outdoor Temperature

Ther

mos

tat,

Deg

rees

F Clear Double Low-E Double

Hours of Discomfort Hours of Discomfort

0

500

1000

1500

2000

2500

< 50°F < 55°F < 60°F

Hou

rs

Clear Double Low-E Double

Summer Comfort IssuesSummer Comfort Issues

Hot Glass

DirectGain

Summer ComfortSummer Comfort

75

80

85

90

95

100

105 HSLE

SingleTintDoubleTintTripleClearDoubleClearSingleClearLSLE

Roo

m-s

ide

Surf

ace

Tem

pera

ture

(90

F ou

tdoo

rs)

Summer Comfort Low-E GlassSummer Comfort Low-E Glass

0% 10% 20% 30% 40% 50% 60% 70% 80%

LSLE

MLSE

HSLE

Clear

Probability of Discomfort

Due to glass temperatureDue to solar gain

0%

10%

20%

30%

40%

50%

60%

70%

80%

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0Slightly Cool Neutral Slightly Warm

Predicted Mean Vote

Pred

icte

d Pe

rcen

t Dis

satis

fied Slightly Cool

Drops PPD from 26% to 6%

Slightly WarmIncreases PPD from 26% to 62%

Solar Offset to PMV100 btu/ft2 = +0.8 PMV PointsSolar Offset to PMV100 btu/ft2 = +0.8 PMV Points

41

Summer DiscomfortSummer Discomfort

0%

10%

20%

30%

40%

50%

60%

100 btu/ft2 200 btu/ft2 100 btu/ft2 200 btu/ft2

No Sun Partial Sun Full Sun No Sun Partial Sun Full Sun

SHGC>0.5 SHGC<0.3

Pred

icte

d Pe

rcen

t Dis

satis

fied

Discomfort in AshevilleDiscomfort in Asheville

As heville

679

24 0 0 0 0 0

766

778643

396172

521357

676

643

542

391

177

452

336

225

141

48

0

0

0

0

0

500

1,000

1,500

2,000

2,500

3,000

3,500

C lear P yro E LoĒ 179 LoĒ 272 LoĒ 366 3P Ē 179 3P Ē 272

Hours of Disco

mfort

S ummerDay

S wingS eas on

WinterDay

WinterNight

Cooling Thermostat Offset25% max PPDCooling Thermostat Offset25% max PPD

70

71

72

73

74

75

76

77

78

100 btu/ft2 200 btu/ft2

No Sun Partial Sun Full Sun

Ther

mos

tat S

ettin

g, °

F

SHGC>0.5 SHGC<0.3

Windows & Comfort SummaryWindows & Comfort Summary•Beware of trade-offs

– “They might be equal, but they’re not the same!”

•Energy models don’t capture comfort implications– T-stat setpoints

“We don’t sufficiently discredit the selection of bad windows…”

Yogi Berra Mathis

Windows Session Wrap-upWindows Session Wrap-up The Code Has ChangedThe Code Has Changed•What is the code?

42

All Together…All Together…•Least safe…•Least strong…•Least energy efficient…



Comfort and WindowsComfort and Windows•How comfortable are you next to an

R-19 wall?– R-13? R-11?

•What about next to the windows?– Still the hottest surface in the house– Still the coolest surface in the house

•Window decisions drive the comfort conditions

Windows and Winter ComfortWindows and Winter Comfort

0

10

20

30

40

50

60

70InsulatedWallLSLE

HSLE

Triple

Double

SingleRoo

m-S

ide

Surf

ace

Tem

pera

ture

0F outside

Windows and Summer ComfortWindows and Summer Comfort

75

80

85

90

95

100

105 HSLE

SingleTintDoubleTintTripleClearDoubleClearSingleClearLSLE

Roo

m-s

ide

Surf

ace

Tem

pera

ture

90F and sunny

outside

Homes Have ChangedHomes Have Changed

49%

91%

40%

50%

60%

70%

80%

90%

100%

1973 2005




RecapRecap•Windows Matter!

– Heating, Cooling, Comfort, etc.•Key performance indices

– U-factor– SHGC– Certified, Whole Product Ratings!

•Turn on the efficiency power plant!

43

Thank you! Any Questions? Consider…Consider…•How many builders equate their

HVAC sizing decisions with their selection of windows?

•Let’s look at the Southeast

IECC Climate

Zone

Window U Wall R Ceiling R

7-8 0.35 21 496 0.35 19 495 0.35 19 384 0.40 13 383 0.65 13 302 0.75 13 301 1.20 13 30

Climate and WindowsClimate and Windows

Low U‐factor Required

Low SHGC Required

The IECC in the Southeast RegionThe IECC in the Southeast Region

Code Requirements in the Southeast RegionCode Requirements in the Southeast Region

Zone WindowU

WindowSHG

C

Ceiling Wall Foundati

on

4 0.40 ---- R38 R13 R10

3 0.65 0.40 R30 R13 R0

2 0.75 0.40 R30 R13 R0

1 1.20 0.40 R30 R13 R0

44

3 Cities in the Southeast Region3 Cities in the Southeast Region

Windows & Energyin the Southeast RegionWindows & Energyin the Southeast Region

SE Window PerformanceSE Window Performance• Compare the changes in heating and

cooling energy across 3 cities in the region as a function of SHGC or U-Factor.

• General conclusions are:– Low SHGC increase heat load but reduces solar

loads to a great extent– U-Factor has minimal impact on cooling, but does

reduce heating loads– The balance between heat and cool shifts between

zones

46

Let’s look at a few of these emerging technologies...

Emerging TechnologiesEmerging Technologies

Multiple glazings and films that do multiple duties.

What USED to be a passive technology is rapidly becoming active.

Old?

Frame MaterialsFrame Materials New Twists on Old MaterialsNew Twists on Old Materials

Aerogels“Foamed glass”Highly insulativeMany advancements in this area.Over R-20 per inchFragility is current weakness.Lots of research underway.

Switchable GlazingsSwitchable Glazings

47

ElectrochromicsSwitchable transmissionRange of solar controlSignificant research underwayMajor implications for utilities and peak loadsCommercial applications first

More Switches….More Switches….Liquid Crystal technologies...

... create new architectural and energy opportunities.

Transmissive State Reflective State

SPDsSuspended Particle Displays

Coming AttractionsComing Attractions•Windows that double as:

– your TV screen– your computer screen

•Windows that are integral components of:– your security system– your audio system– your water management system

A Window on the Future: Fenestration Fundamentals ... · Construction 34.1 Remodeling 17.2...

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