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Passive House NorthwestAIA CEU Provider

Window Workshop-A Window on the Future

Course# 021518-phnw

Daniel Haaland, RDH Building Science

February 15th, 2018

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Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This course is registered with

AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or product.___________________________________________

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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This presentation will address a range of design and performance characteristics relevant to those who select, and specify windows for durability and energy efficiency.

CourseDescription

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LearningObjectives

1. Audience members will understand the fundamentals of window performance from a thermal and comfort performance perspective including surface temperature, cold air drafts, and overheating

2. Audience members will understand the heat transfer mechanics in window frame and glass components, and the technologies used to improve thermal performance..

3. Audience members will understand the significance of installation details on the effective thermal performance of windows and will be advised of ways to mitigate the thermal performance loss..

4. Audience will learn how durability of the building envelope can be affected by proper installation of high-performance windows.

At the end of the this course, participants will be able to:

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Course Approved for CPHC® Continuing Education Credits

LEARNINGOBJECTIVESBuilding Science of High-

Performance Windows

1. Understand the fundamentals of

window performance for thermal

comfort.

2. Understand the heat transfer

mechanisms in window frame & glass

components

3. Understand the significance of

installation details on effective thermal

performance

4. Learn how durability of the building

envelope can be affected by proper

installation

Earn 1 CPHC CEUSelf-report link:www.phius.org/cphc/self-report

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The Motivation

The Building Science of Windows

The Universe of U-values

The Path to High-Performance

Outline

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Cheap

Durable

Fast

Comfortable

Healthy

Energy Efficient

Resilient

Adaptable

Easily Renewed/Repaired

…

Definition of High Performance

Mostly talking about this today, but

also impacts others.

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The Motivation

The Building Science of Windows

The Universe of U-values

The Path to High-Performance

Outline

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Recent window attention – why?

Windows significantly influence

the performance of the whole

building envelope.

Essentially, windows are the

weakest thermal element in the

building envelope.

Think about what R-3 windows

do to R-20 insulated walls.

The technology and products

already exist in the market to

significantly improve window and

thus whole-building thermal

performance

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Where is heat loss occurring?

Yellow/red/white = hot = high heat flow/high U-value– Blue = Cold = low heat flow/low U-value

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Window to Wall Ratio Impacts

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Cold glass causes discomfort

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Typical Window (Uw = 0.35 Btu/hr·ft²·˚F)

Source: Passive House Institute

17°C

20°C

Cold glass causes stratification

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Warm glass does not require a radiator

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What’s in a Window?

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Review of Window Types & Terminology

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Window frame materials

Aluminum

Vinyl, PVC

Wood

Fiberglass

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Hybrid and advanced window frames

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Air Barrier

Insulation

Control functions in fenestration

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AB

Insulation

Control functions in fenestration

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AB

Insulation

Control functions in fenestration

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AB

Insulation

Control functions in fenestration

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Insulating Glazing Units = IGUs

IGU Components:

1. Surface 1 (exterior)

2. Surface 2 (interior side

of exterior lite)

3. Surface 3 (exterior side

of interior lite)

4. Surface 4

5. Low-e coating

6. Edge spacer (separate

glass panes)

7. Desiccant (to dry air)

8. Primary edge seal

(vapor)

9. Secondary edge seal

(structure)

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Heat flow through an IGU

Losses Gains

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Low-e CoatingsControl Radiation

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Low-e coatings

Low-emissivity (Low-e) thin metallic

coating: changes optical properties

(visible, Infrared, UV), is spectrally

selective, reduces emissivity of glass

surface

Soft Coat (Sputtered) – very low

emissivity, good U-values, typically

lower solar heat gain

Hard Coat (Pyrolytic) – moderately

low emissivity, U-values not as low as

soft coat, higher solar heat gain

U-factor Versus Low-E Coating Emittance

0.2

0.3

0.4

0.04 0.08 0.12 0.16 0.2 0.24

Coating Emittance

U-f

ac

tor

(im

per

ial)

Air U-factor Argon U-factor

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Influence of low-e coatings on U-value – Triple glazing

25%

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Edge deletion

Typical full edge

deletion

Incomplete edge

deletion

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Low-e corrosion & delamination

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Gas Filled LayersThe center of window performance

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Influence of gas fill on U-value – Triple glazing

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Argon fill failures

2 recent projects in North America – Glazing Units from one

Manufacturer

Argon was specified

Tested ~100 units in the field at 2 job sites

IGUs were manufactured 1-4 months previously

Argon concentration varied:

› 3% of units had concentrations above 90% Argon

› 25% between 75-90%

› 11% between 50-75%

› 61% had below measurable

Largely batch related consistencies

No apparent loss with age

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Edge Spacers

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Types of IGU edge spacers

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Standard Aluminium Stainless-steel “Thermix“

49 ˚F 53 ˚F 55 ˚F

Calculation of the window U-value with:

Ug = 0.12 Btu/(hr ·ft²·F)

Uf, = 0.13 Btu/(hr ·ft²·F)

Source: PHI Berthold Kaufmann

Uw 0.157 Btu/(hr ·ft²·F) Uw 0.146 Btu/(hr ·ft²·F)

(-7%)

Uw 0.140 Btu/(hr ·ft²·F)

(-11%)

Thermally improved spacers decrease the window U-value and raise internal surface temperature

Thermal performance of IGU edge spacers

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Defect in edge seal = fogged IGU

Single Seal IGUs have limited

lifespan.

Hot-melt, butyl, swiggle,

polysulfide

IGU seal under very large stresses

from thermal, wind pressure.

Several thousands of Pascals

Always specify a dual seal IGU

PIB primary seal (moisture),

Silicone secondary seal

(structural) excellent track

record

Failures of IGU edge spacers

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Sagging spacer bar

IGUs under negative pressure due to elevation change

Thermoplastic sealant crept at high temperatures

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Solar ShadingKeeping it cool

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Solar heat gain

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Sunny day breaks

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Thermal stress breakage

Breakages occurred on sunny days on elevations with solar shades

Annealed glass was specified and installed

Breaks always intersect at 90 degrees to edge

Installation of glazing units conformed to IGMA guidelines

Conclusion: Thermal stress breakage

A 50 degree Fahrenheit difference in glass temperature is often

sufficient to cause breakage of annealed glass. Solar shading allows

part of the glass to be exposed to the sun while shading other parts of

the same lite causing a significant temperature difference. Reflective

coatings and solar selective low-e coatings compound this effect.

Heat strengthened glass should always be used on projects with

solar shading devices or when using reflective or heat absorbing

glass products.

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The Motivation

The Building Science of Windows

The Universe of U-values

The Path to High-Performance

Outline

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It can be a bit confusing...

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ISO vs NFRC

European standard: ISO

International Organization

for Standardization (ISO)

ISO 10077-1 and 10077-2

for frame and whole window

U-value

EN 673 for glazing U-value

EN 410 for glazing solar

heat gain (g-value)

Passive House

Modified ISO

North America: NFRC

National Fenestration Rating

Council (NFRC)

NFRC 100 for U-value, NFRC

200 for SHGC

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ISO vs NFRC: Differences

Boundary conditions

(temperatures & air film

resistances)

Standard size of window

Method of accounting for edge

of glass effects

Calculation methodologies

(algorithms) for glazing unit

airspace, frame U-value

SHGC (g-factor) for whole

window or centre of glass

Treatment of sloped glazing

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How do these differences affect performance?

RDH study evaluated U-value, solar heat gain of three windows

using NFRC and ISO/PHI methods

North American Vinyl Frame

North American Fibreglass Frame

European Vinyl Frame

Each window had same

glass, gas fill and spacer

Showed how same product

performs under different rating

systems

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Key difference: Centre of Glass U-Value

Triple glazing, argon gas fill, two low-e coatings

Big difference between U-values for NFRC and ISO methods

at standard temperatures

0.5

0.6

0.7

0.8

0.9

10 12 14 16 18 20

Ce

ntr

e o

f G

lass

U-V

alu

e,

W/m

2-K

Gap Size, mm

NFRC, -18°C

ISO, 0°CNFRC optimal gap size is approx. ½”

ISO optimal gap sizes are larger, approx. 5/8”

(-0.4 ˚F)

(32˚F)

(0.12)

(0.14)

(0.16)

(0.10)

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ISO vs NFRC: Edge effects

Uframe x Aframe

Uglazing x Aglazing

Uedge x Aedge2.5”

NFRC U-Value

Uframe, Uedge, Uglazing used to calculate overall U-value

Passive House U-Value

Uframe x Aframe

Uglazing x Aglazing

ψspacer x L glazed perimeter

ψinstall x L window perimeter

Uframe, ψspacer, Uglazing, ψinstall

entered into PHPP

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ISO vs NFRC: Edge effects

Passive House/ISONorth America/NFRC

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No simple conversion method

Neither NFRC nor ISO system is better for all

applications

Today products are optimized to perform best

under the rating regimes in effect in Europe, North

America

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The Motivation

The Building Science of Windows

The Universe of U-values

The Path to High-Performance Windows

Outline

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The Perpetual Question

+ ?

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We have come a long way

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21st Century

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Continually evolving best practices

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Fundamentals: Following & connecting the critical

barriers

Water Shedding Surface (WSS)

Water Resistive Barrier (WRB)

Air barrier (AB)

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So what is changing?

Trend towards more efficiently

insulated building enclosures due to

higher energy code targets & uptake

of passive design strategies

Greater attention to reducing thermal

bridging in building enclosures

Window installation practices are

evolving to incorporate new and/or

imported window frames into more

highly insulated wall

Ongoing need to balance thermal

and durability considerations

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Old window installation details aren’t often good

enough for high-performance projects

Key considerations:

• Avoid metal flashings that bypass

framing or insulation

• Reduce wood framing around window

• Over-insulate the window frames where

feasible

• Air tight (and properly water managed)

Too much

insulation

displaced &

too large of

metal flashing

Too much

wood

Too much

wood

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Thermally improved window details

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Window Psi–Install

������� � � �

Window installation heat loss is the additional heat flow through the interface,

gap, framing, flashings, etc., between the wall and window

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Psi-Value Case Study: What matters & how much?

Window:

Fiberglass fixed window with high

performance triple glazing

(U-0.125, R-8.0)

Walls:

Split insulated 2x6 wood frame

filled with fiberglass batt and 6”

exterior mineral wool with long

screws through insulation to

support cladding

(R-40 effective)

Windows installed at inner, middle

and exterior of wall

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Standard install

U-value gets 18% worse just

by installing it into the wall!

14.7oC

58.5oF

13.1oC

55.6oF

Uwindow = 0.145 (Btu/ft²∙°F∙hr)

Ψinstall = 0.028 (Btu/hr∙°F·ft)

Uinstalled = 0.171 (Btu/ft²∙°F∙hr)

%change = 18% (worse)

Rinstalled = 5.8 (hr·ft2· oF/Btu)

14.7oC

58.5oF

Ψ = 0.022 (Btu/hr·°F·ft)

Ψ = 0.049 (Btu/hr·°F·ft)

Ψ = 0.023 (Btu/hr·°F·ft)

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Impact of placement in R.O. – No over-insulation

Based on window size of 4.0 x 4.9 ft

Window towards

the exterior is

better thermally,

small impact on

interior surface

temperatures

Inner Middle Outer

Uwindow (Btu/ft²·°F·hr) 0.145

Ψinstall (Btu/hr·°F·ft) 0.031 0.028 0.021

Uinstalled (Btu/ft²·°F·hr) 0.173 0.171 0.165

%change (%) 19% 18% 13%

Rinstalled (hr·ft2· oF/Btu) 5.8 5.9 6.1

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Over-insulating frames

16.3oC

61.3oF

13.1oC

55.6oF16.3oC

16.3oF

Ψ = -0.006 (Btu/hr·°F·ft)

Ψ = 0.049 (Btu/hr·°F·ft)

Ψ = -0.005 (Btu/hr·°F·ft)

18% loss in

window

U-value for no

over insulation vs

4% with

Watch temperatures if insulating on inside!

If over-insulating at sill watch drainage!

Uwindow = 0.145 (Btu/ft²∙°F∙hr)

Ψinstall = 0.006 (Btu/hr∙°F·ft)

Uinstalled = 0.151 (Btu/ft²∙°F∙hr)

%change = 4% (worse)

Rinstalled = 6.6 (hr·ft2· oF/Btu)

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Building description

6-storey apartment building, 60+ residential units constructed

over two levels of below grade parking spaces.

RIP-10 walls & UIP-0.36 thermally broken aluminum windows

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Typical approach

U-Factors are assigned to the areas

Uwall,3Uwindow,1

Uwall,1

Uwall,2

Uwindow,2

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Effective building enclosure R-Value

Windows are 24% of

the area, but 57% of

the heat flow.

6.5

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A

B

θsi minA-B

= 1.59 o

C

fRsi

= 0.386

A

B

θsi minA-B

= 8.88 o

C

fRsi

= 0.629

A

B

20.0 o

C

16.0 o

C

12.0 o

C

8.0 o

C

4.0 o

C

0.0 o

C

-4.0 o

C

-10.0 o

C

θsi minA-B

= 8.88 o

C

fRsi

= 0.629

A

B

20.0 o

C

16.0 o

C

12.0 o

C

8.0 o

C

4.0 o

C

0.0 o

C

-4.0 o

C

-10.0 o

C

θsi minA-B

= 1.59 o

C

fRsi

= 0.386

Window uninstalled vs. installed

U-0.38

(R-2.6) U-0.59

(R-1.7)U-Value 55%

Ψinstall

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Case study – Impact on overall effective enclosure

Uninstalled

Installed

6.5

4.9

Window install can

reduce overall

enclosure thermal

performance by 33%!

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Key Conclusions

Windows have a large part to play in

the overall performance of our

enclosures

Long history of iterative progress in

the design of and installation of

windows – many past failures and

successes

Evolution is continuing with higher

performance windows

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Discussion + Questions

FOR FURTHER INFORMATION PLEASE VISIT

www.rdh.com

www.buildingsciencelabs.com

OR CONTACT US AT

dhaaland@rdh.com

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This concludes The American Institute of Architects Continuing Education Systems Course

Info@PHnw.org

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Course Approved for CPHC® Continuing Education Credits

REMINDERSELF-REPORT CPHC CEUs

Self-report link:www.phius.org/cphc/self-reportEnter verification code: 21235

Earn 1 CPHC CEU