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NNCA Construction Workshop 2016-02-17

G.Finch - RDH 1

Picking Windows & Glazing Units for Optimal Energy Efficiency in the North

NNCA RESIDENTIAL CONSTRUCTION WORKSHOP, YELLOWKNIFE – FEB 17, 2016

GRAHAM FINCH, MASC, P.ENG – PRINCIPAL, BUILDING SCIENCE RESEARCH SPECIALIST

[email protected] – 604-873-1181

Outline

� Understanding Window

Performance Numbers & What

It All Means

� Energy Regulations and

Available Window Products in

Canada’s North

� Picking Optimal Windows for

Northern Canadian Homes –

Balancing Energy and Comfort


G.Finch - RDH 2

Why The Focus on Windows?

� Are a focal architectural and

function part of our homes (views,

daylighting, aesthetics)

� Can be one of the biggest

components of heat loss in a

building (20-50% range)

� But they can also gain an

appreciable amount of heat, which

can be good to reduce space-heat

loads – or it can also be bad and

cause overheating and discomfort

� Picking windows is a learned

experience of conflicting priorities

and a fairly technical one at that!

The Simple Solution to Windows?!


G.Finch - RDH 3

How do YOU Pick a Window?

� Frame & Glazing Considerations

� Aesthetics, Colour, Look & Feel?

� Materials?

� Hardware & Accessories?

� Technical Performance &

Specifications?

� Thermal

� Air-tightness

� Water-resistance

� Security

� Condensation Resistance

� Code Requirements & Other?

Picking Frames

� Frame Material

� Vinyl

� Aluminium

� Wood

� Fiberglass

� Hybrid Combinations

� Dimensions/Thickness

� Structural Performanace

� Aesthetics/Colours/Feel

� Thermal Performance (U-value)

� Hardware Integration

� Installation Method (Flange/Rebate)


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Picking Glass and Glazing

� Insulated Glazing Units (IGUs)

� Double/Triple/Quad Glazing

� Inert Gas Fill (Air, Argon, Xenon,

Krypton)

� Aesthetics

� Colour (Clear, Green, Blue, Grey etc.)

� Clarity (Visible Light Transmission,

VLT)

� Reflection (Inside & Out)

� Technical Specifications

� U-value

� Solar Heat Gain Coefficient (SHGC)

� ER value

� UV Blocking

� Spacer Bars/Edge Seals

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 (interior)

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)

Air/gas filled space(s)With triples – add in surfaces 5&6With quads – add in surfaces 7&8


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Triple & Quad IGUs

� More air/gas spaces = lower (better) IGU

U-values

� Argon minimal cost to add

� Argon does not leak out through dual seal

spacer bars appreciably unless a defect

� More glass = lower SHGC values

� Fundamental law with stacking layers of

glass together, even clear non-low-e glass

� Can get good range of SHGC values from

low to high for available triple units

� Low-e coatings typically put on cavity side

of inner and outer panes of glass within

triples/quads

� Concerns with glass breakage increases

with more layers of glass

� From experience – durability of glass

triples/quads is better than thin

suspended plastic film systems

Free program by LBNL, called WINDOW allows you to design your own IGUs and get all of the optical properties

Hard Coat vs. Soft Coat Low-e Coatings

� Both thin metal films (silver,

tin, stainless steel etc.) & anti-

reflective metal-oxide films

applied to glass

� Hard coat (pyrolytic) applied

during float process of making

glass

� Tends to result in higher SHGC

but lower thermal performance

(higher U-values)

� Soft coat (sputtered) applied to

glass anytime

� Tends to result in lower SHGC

but better thermal performance

� Newer coatings can get best of

both worlds high SGHC, high

thermal performance Images from PPG


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How Low-e Coatings Work

UV

Images from LBNL

Aesthetics, Colour, & Reflection


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Visible Light Transmission

� Visible Light Transmission (VLT) is the visible light

spectrum that is transmitted through the glazing unit

� Important in day-lighting and glare control

� Typical range of 30-70%, optimum depends on use of

space and window to wall ratio

Solar Heat Gain Coefficient (SHGC)

� SHGC is the % of total solar radiation

transmitted as heat-gain through an

IGU (window)

� SHGC of 0.55 = 55% transferred to

interior (directly by short wave

radiation and indirectly by absorption

and long-wave radiation)

� Remainder is reflected or absorbed

and re-radiated back out

� Too high of SHGC can cause over-

heating within highly glazed spaces

� Not high enough SHGC can limit

amount of potential “free” heat gain

that may be beneficial in heating

climates

SHGC for a window includes the frames, hence why operable windows have lower SHGCs overall


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U-values for IGUs

� U-value for a IGU is driven

by the low-e coating

emissivity, gas fill and gap

width

� Lower emissivity coatings

tend to be soft-coat silver

� Argon gas provides ~25%

improvement in U-value

� Optimal gap is ~1/2” to

5/8” for air/argon - or so

you would think…

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-factor (im

peria

l)

Air U-factor Argon U-factor

U-factor Versus Argon Fill Concentration

0.22

0.24

0.26

0.28

0.30

0.32

0 10 20 30 40 50 60 70 80 90

Argon Fill Concentration (%)

U-facto

r (im

peria

l)

IGU U-values – Gap Widths and NFRC vs ISO

� NFRC (North American) and ISO (European) Standards do not

agree on calculation procedures for center of glass U-values

� Outdoor temperature also matters (i.e. U-values are not fixed)

0.5

0.6

0.7

0.8

0.9

10 12 14 16 18 20 22 24

Ce

ntr

e o

f G

lass

U-V

alu

e,

W/m

2-K

Gap Size, mm

NFRC, -18°C

NFRC, -7°C

NFRC, 0°C

NFRC, 5°C

ISO, -18°C

ISO, -7°C

ISO, 0°C

ISO, 5°C

USI-0.71UIP-0.125 (R-8)

USI-0.52UIP-0.092 (R-10.8)

Triple Glazed IGU 2 Low-e Coatings


G.Finch - RDH 9

Overall Window U-values

Window U-value =

Frame U-value x

% Frame Area

+

Center of Glass U-value x

% Glass Area

+

Edge of Glass U-value x

% Edge of Glass Area

Overall R-value =

1/U-value

Center of Glazing

U-value

Frame U-value

(Operable & Fixed Frames)

Edge of Glazing

U-value

Window ER Values

� ER Value is a numerical combination of the window U-value,

SHGC and air-leakage rate – for single family homes

� Aimed at consumers, higher number is better

� Used within NBC & Energy Star® to incentivize better energy

performance windows (lower U-value & higher SHGC) favoured)

� Better to use SHGC & U-value in the Far North


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Wading through the Technical Specs of IGUs

Indoor

Trans. UV Tdw

Clear % % Out % In SHGC SC Air Argon WinterSummer Trans ISO/CIE

Clear IG 82% 15% 15% 0.78 0.89 0.48 0.46 45 90 58% 75%

LoE Products - Sputtered

Cardinal LoE²-272 #2 (e=.041) 72% 11% 12% 0.41 0.47 0.30 0.25 56 84 16% 55%

Cardinal LoE²-272 #3 (e=.041) 72% 12% 11% 0.50 0.57 0.30 0.25 56 98 16% 55%

Cardinal LoE²-270 #2 (e=.036) 70% 12% 13% 0.37 0.42 0.29 0.25 56 93 14% 53%

Cardinal LoE²-270 #3 (e=.036) 70% 13% 12% 0.45 0.53 0.29 0.25 56 99 14% 53%

Cardinal LoE3-366 #2 (e=.022) 65% 11% 12% 0.27 0.31 0.29 0.24 56 83 5% 43%

Cardinal LoE3-366 #3 (e=.022) 65% 12% 11% 0.39 0.45 0.29 0.24 56 101 5% 43%

PPG SolarBan 60#2 (e=.043) 71% 12% 13% 0.39 0.45 0.30 0.25 56 95 16% 53%

Viracon VE-2000 #2(e=.040) 72% 11% 12% 0.38 0.44 0.26 0.25 56 84 11% 52%

Guardian Perf. Plus ll #2(e=.044) 69% 19% 17% 0.41 0.47 0.30 0.25 56 65 20% 50%

AFG Comfort TIAC #2(e=.036) 62% 23% 29% 0.40 0.46 0.29 0.25 56 85 30% 51%

AFG Comfort TIR #2(e=.034) 71% 21% 19% 0.47 0.54 0.29 0.25 56 85 30% 57%

AFG Comfort TIPS #3(e=.047) 77% 13% 14% 0.60 0.69 0.30 0.25 56 94 33% 63%

LoE Products - Pyrolytic

AFG Comfort E2 #3 (e=.204) 76% 16% 14% 0.73 0.85 0.35 0.31 53 101 44% 64%

Pilk/LOF Energy Adv. #3,(e=.153) 75% 18% 17% 0.72 0.82 0.33 0.29 54 100 45% 65%

Pilk/LOF Solar E #2(e=.153) 54% 10% 16% 0.48 0.55 0.33 0.29 54 91 40% 52%

PPG Sungate 500 #3,(e=.215) 76% 18% 17% 0.71 0.81 0.35 0.31 52 99 49% 66%

PPG Sungate 300 #3 (e=.324) 76% 18% 18% 0.71 0.82 0.38 0.34 51 96 56% 66%

Glass Temp (F)(Btu/hr/ft²/°F)

Center of Glass

U-Factor

Reflectance

Visible Light

IGU Spacer Bars

� Lots of options – look for

lower conductivity & dual

edge seal technology

� PIB primary seal (vapour),

silicone secondary seal

(structural) works well

� Avoid single seal systems

� Not all created equal


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Conduction through IGU Spacer Bars

Failed IGUs from Bad Spacer Bar Choices


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Condensation & Frost Prevention

� Condensation/frost occurs

when the surface

temperature of the window

drops below the dewpoint

temperature of the

surrounding air

� Causes:

� Inadequate window frames or

IGU spacer bars

� Curtains or blocked interior

airflow

� Poor installation of window

frame

� Too high indoor dew-point

� Poor heating system

configuration

Condensation & Frost due to Hardware Problems


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Frost From Poor Window/Door Selection

And Don’t Forget to Close the Window..


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Window Frame Design & Condensation Risk

� Every window has a slightly different condensation

potential & many factors involved

� More conductive frame materials tend to be colder, but also

bring heat from the frame to the edge glass

� Massing of frame material inboard or outboard of thermal

break or IGU matters

� Operable units tend to perform worse than fixed units (frame

profile & air leakage)

� IGU spacer bars matter for edge of glass & frame

temperatures

� Glazing stop material also matters

� Glazing matters – double vs triple glazing, low-e coating

location, and interior surface low-e coatings

� Placement of window in rough opening can be important

Frame Profile/Massing & Condensation Potential

Exterior -18°C Interior 21°C

1.7°C

11.4°C

5.0°C

5.3°C

4.3°C

7.4°C


G.Finch - RDH 15

Glazing Stops - PVC vs Aluminum with an Aluminum Frame

-0.2°C

2.8°C

PVC Glazing StopAluminum Glazing Stop

14.8°C

3.4°C

3.7°C

3.6°C


Window Frame Types & Condensation Potential

Thermally Broken Aluminum Reinforced Vinyl Fiberglass


Edge of IGU slightly warmer with aluminum

Frame colder with aluminum


G.Finch - RDH 16

Frame Design – Triple Glazed Vinyl


2.8°C6.9°C

Wood vs Aluminum Curtainwall – Subtle Tradeoffs

-1.9°C

5.1°C

Frame = R-2.6

Frame = R-2.0


wood Warmer frame

Colder frame


G.Finch - RDH 17

Double vs. Triple Glazing

8.9°C2.6°C

Exterior -18°C Interior 21°C Exterior -18°C Interior 21°C

Condensation on the Exterior of Windows


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Rating Condensation Resistance of Windows

� Temperature Index (I-value) – CSA A440

� Measured in Lab – coldest location

� Is value that can also be checked in the field - preferred

� Condensation Resistance Factor (CRF) – AAMA

� Measured in Lab – weighted cold location (relative metric)

� Condensation Resistance (CR) – NFRC

� Simulated – weighted factor accounting for range of indoor RH levels (30,50,70%) and fixed outdoor conditions

� All factors are different and cannot be correlated

� In all cases a higher number means a better product with lower potential for condensation

Temperature Index (I-value)

� Measure of a window’s

condensation resistance (higher

better)

� I-value = 100 x (TF - TO)/(TI – TO)

� TF = Frame temperature (worst),

TI and To = inside and outside

temp.

� Can be used to help select

windows based on exterior

design conditions and interior RH

expectations


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Selecting I-values by Winter Design Conditions

0

10

20

30

40

50

60

70

80

90

100

0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50

Te

mp

era

ture

In

de

x (

I)

January 2.5% Design Temperature

60% Indoor RH

50% Indoor RH

40% Indoor RH

30% Indoor RH

Edmonton WhitehorseYellowknifeResolute

Vancouver

CSA A440.2-2009

Other Considerations - Window Air-Leakage Rates

� Leakage occurs at frame joints/glazing interfaces,

gaskets & operable hardware

� Air leakage ratings in CSA A440-00 and NAFS-08

Window Rating

CSA A440-00 NAFS-08

Max air leakage rate, m3/h/m

Max air leakage rate, converted to L/s/m2

(NFRC Standard Size Window)

Max air leakage rate for R Class,

L/s/m2

A1 2.79 1.86 n/a

A2 1.65 1.10 1.5

A3 0.55 0.37 0.5

Fixed 0.25 0.17 0.2


G.Finch - RDH 20

Energy Codes & Available Windows in the North

Energy Code Requirements & Regulations for Windows in the North

� NBC Part 9.36 (Houses) Zone 8

� Maximum U-value USI-1.4

(UIP-0.25) or minimum ER of 29

� Is a vinyl, fiberglass or wood

frame window with triple glazing

(air filled non low-e) or argon

filled double glazing with dual

low-e coatings (#2 & #4 surfaces)

� Energy Star® North Zone

� Maximum U-value of USI-1.2

(UIP-0.21) and ER ≥24, OR

minimum ER 34

� NECB 2011 (Larger Buildings)

Zone 8

� Maximum U-value of USI-1.6

(UIP-0.28)


G.Finch - RDH 21

Additional Requirements Influencing Window Selection

� Yukon

� NBC 9.36 requirements adopted in April 2013

� Whitehorse Green Building Standard – Energuide 82 or better

� Whitehorse building bylaw – maximum window U-value USI-

1.4 (UIP-0.25)

� Northwest Territories

� Yellowknife Building Bylaw – Energuide 80 or better home

� Typically see triple pane vinyl with argon and one low-e

coating

� Nunavut

� Nunavut Housing Corporation – minimum Energy Star®

Northern Zone, maximum USI-1.2 (UIP-0.21)

� Local supply is more challenging that YT and NT with limited

options and replacement parts etc.

Northern Canada Window Suppliers and Local Preferences

� Vinyl framed triple glazed windows common for homes

� Apparently not a lot of U-value labelling happening - though

understood that triple glazed vinyl or fiberglass meets code

� Seeing mix of argon filled non low-e triple glazing and argon

filled dual low-e triple glazing

� Anecdotes of medium low solar heat gain being preferred and

both northern and southern suppliers expressed doubt of merits

for passive solar gains in the North – concerns of overheating

discomfort

� Anecdotes that sliding windows easier to maintain than crank

operated casements (from remote communities)

� Interestingly quad-pane makes up 20-25% of local sales for one

northern supplier

� Northern Suppliers

� Northerm (Whitehorse) and Arctic Front Windows (Hay River)

� Several Southern Supplies actively providing products

� Ply Gem, All Weather, Kohltech, JeldWen, Gentek, Cascadia


G.Finch - RDH 22

Available Glazing Units

� Four major suppliers of low-e coated glass to the residential

window industry: Cardinal, Guardian, PPG and AGC

� All make double and triple glazed units, harder to get quads

made from major suppliers

� Each supplier has products available that can be categorized as

having low, medium and high solar heat gain properties

� Minor costs differences between coatings and manufacturers

� Glazing cost is minor (~$5/sqft) compared to the overall cost of a

window (avg $50/sqft in Yellowknife)

� Argon gas fill is fairly standard and often available at minimal

cost

� Note about Hot2000 – enter actual window properties from

manufacturer – do not let H2K calculate it

Selecting Optimal Windows for Energy Efficiency


G.Finch - RDH 23

Window Selection for Energy & Thermal Comfort

� Winter Goals

� Minimize heating energy

� Improve thermal comfort by

reducing cold surfaces

� Low U-values, High SHGC

� Summer & Swing Season Goals

� Minimize overheating to

prevent or reduce cooling

needs

� Improve thermal comfort by

reducing surface temperatures

and indoor gains

� U-values not as important,

Lower SHGC more valuable

Optimal Window for Northern Housing

� Study performed by RDH

with CMHC to look at optimal

window selection for a

representative northern

housing archetype

� Above permafrost

construction, single storey

with heated “crawlspace” for

services

� 1000 sq.ft house with 10%

window to wall ratio

� While one archetype chosen

here, the findings can be

readily extrapolated to other

and larger housing designs


G.Finch - RDH 24

Energy Modeling Assumptions

� 4 occupants

� Standard NBC/NECB set-point and

appliance/plug load assumptions

unless more detailed northern

modifications mde

� R-40 effective walls, R-60 roof,

R-40 floor, 1.5ACH airtightness

� Oil heat & hot water (80% efficient)

in NT/NU, electric in YT

� Ducted HRV, 60% efficient

� Starting window assumption,

USI-1.4 (UIP-0.25), SHGC 0.26

� Modeling compared to NRCan

benchmarks for similar homes

Room Electricity

5%Lighting4%

System Fans0%

Heating (Oil)71%

DHW (Oil)20%

Room Electricity12%

Lighting8%

System Fans0%

Heating (Electricity)

46%

DHW (Electricity)

34%

Whitehorse$2400

Yellowknife$4800

Optimal Window Study – Study Locations

2010 NBC CLIMATIC INFORMATION FOR NORTHERN LOCATIONS.

Whitehorse Yellowknife Resolute

Latitude 60.7 ͦN 62.4 ͦN 74.7 ͦN

Climate Zone 7B 8 8

Heating Degree Days (HDDs) 6580 8170 12360

January 2.5% Design Temperature -41 ͦC -41 ͦC -42 ͦC

Assumptions for modeling (2015):• Electric heat in Whitehorse at $0.16/kWh

• Fuel oil in Yellowknife and Resolute at $1.17/L ($0.128/kWh)

• Easily scalable for other regions & fluctuating prices


G.Finch - RDH 25

Impact of Window U-value as Only Variable

� Archetype home heating cost savings for various window U-values

compared to the NBC 9.36 maximum U-value of 1.40 SI (0.25 IP)

-$100

-$50

$-

$50

$100

$150

$200

$250

$300

0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

Annual Home Heating Cost Savings

Window U-Value (W/m2-K)

Whitehorse Yellowknife Resolute NBC 9.36 Maximum U-Value

(0.14) (0.18) (0.21) (0.25) (0.28)

Impact of SHGC as Only Variable

� Archetype house heating cost savings for various window

SHGC values compared to a baseline value of 0.26.

-$100

-$50

$-

$50

$100

$150

$200

$250

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55


Window Solar Heat Gain Coefficient (SHGC)

Whitehorse Yellowknife Resolute NBC 9.36 Baseline SHGC


G.Finch - RDH 26

Selecting Windows in the North Based on ER?

� Typical house heating cost savings for various window ER

values compared to the NBC 9.36 baseline value of ER 29.

Note two different products with the same ER of 34 yield different heating energy consumption due to the differences in U-value and SHGC.

-$200

-$100

$-

$100

$200

$300

$400

25 30 35 40 45 50


Energy Rating (ER)

Whitehorse Yellowknife Resolute NBC 9.36 Baseline ER

Typical Northern Housing Window Combinations

SAMPLE WINDOW PRODUCTS AVAILABLE & SUITABLE FOR CANADAS NORTH

Configuration*Low-E

Coatings**

Operable Unit Performance***

USI (W/m2-K)U-Value

(Btu/hr-ft2-F)SHGC

Triple Glazed, Vinyl Frame, 1 Low-e Coating

LoE 180 1.25 0.22 0.38

LoE 366 1.25 0.22 0.17

LoE 270 1.25 0.22 0.22

Triple Glazed, Vinyl Frame, 2 Low-e Coatings

LoE 180/180 1.08 0.19 0.36

LoE 366/180 1.02 0.18 0.16

Triple Glazed, Fibreglass Frame, 2 Low-e Coatings

LoE 180/180 1.19 0.21 0.28

LoE 366/180 1.17 0.21 0.13

LoE 270/180 1.19 0.21 0.17

Triple Glazed, Passive House Frame, 2 Low-e Coatings

LoE 180/180 0.86 0.15 0.37

LoE 366/180 0.84 0.15 0.17

Quad Glazed, Vinyl Frame, 2 Low-e Coatings

LoE 270/270 0.73 0.13 0.24

*All configurations include argon gas fill and warm edge spacers.**Low-emissivity glass from Cardinal line of products shown as an example; other glass manufacturer’s products are available with similar performance characteristics.*** Performance characteristics shown are values calculated in accordance with NFRC 100 and 200 for operable configurations of actual products. All products’ operable units are casements, except Passive House units are tilt and turn.


G.Finch - RDH 27

Archetypical House Heating Cost Differences

� Typical house heating cost savings relative to the highest U-value

product (Vinyl frame with Cardinal LoE 366, U-0.22, SHGC 0.17).

-$50

$-

$50

$100

$150

$200

$250

$300

$350

Vinyl 366 Vinyl 180 Vinyl 270 Vinyl180/180

Vinyl366/180

Fibreglass180/180

Fibreglass366/180

Fibreglass270/180

VinylPassiveHouse180/180

VinylPassiveHouse366/180

Quad Vinyl270/270



Influence of Window to Wall Ratio

� Typical change in home heating energy costs for various WWRs

compared to a baseline value of 10% (USI-1.40, SHGC-0.26).

-$700

-$600

-$500

-$400

-$300

-$200

-$100

$-

$100

$200

5% 10% 15% 20% 25% 30%


Window to Wall Ratio



G.Finch - RDH 28

Influence of Window Orientation

� Typical change in home heating energy costs for windows

facing various cardinal directions compared to a house with

equal window area in all directions.

-$120

-$100

-$80

-$60

-$40

-$20

$-

$20

$40

$60

$80

0 45 90 135 180 225 270 315 360


Window Orientation (Degrees) Measured from South


NorthWest East

Benefits of Insulated Shutters

� Typical heating energy savings for a house with various exterior

shutter configurations compared to a house without exterior

shutters

Insulated shutters (R-11) versus uninsulated (R-1) are shown. “Tight” installation refers to shutters that are installed as airtight as possible against the wall or window; “loose” installation refers to cases where outdoor air bypasses the shutters.

$-

$10

$20

$30

$40

$50

$60

$70

$80

$90

Closed at Night,Loose Installation

Closed at Night,Tight Installation

Closed Below -10 C,Loose Installation

Closed below -10 C,Tight Installation


Shutter Operation

Insulated Whitehorse Uninsulated Whitehorse

Insulated Yellowknife Uninsulated Yellowknife

Insulated Resolute Uninsulated Resolute


G.Finch - RDH 29

Selection of Windows for Comfort in the North

� Lower U-value windows will always be more comfortable

and have less drafts than high U-value windows during

the cold winter months

� Challenge is balancing the SHGC for the potential

wintertime gain vs swing season/summer overheating

� Comfort can be difficult to quantify, however can look

at window surface temperatures, air temperatures and

“operative temperatures”

Comfort Analysis & Glazing SHGC Selection

� Archetype Northern Home, West Zone Operative Temperature, June 21st –

Example with windows closed/poor ventilation – extreme case

Whitehorse

SHGC 0.26, No Shutters



SHGC 0.26, Shutter closed when direct sun

SHGC 0.26, Shutters closed when indoor air temp is greater than 21

24

26

28

30

32

34

36

38

40

1:0

0

3:0

0

5:0

0

7:0

0

9:0

0

11

:00

13

:00

15

:00

17

:00

19

:00

21

:00

23

:00

Tem

pe

ratu

re (

°C)

24

26

28

30

32

34

36

38

40

1:0

0

3:0

0

5:0

0

7:0

0

9:0

0

11

:00

13

:00

15

:00

17

:00

19

:00

21

:00

23

:00

Tem

pe

ratu

re (

°C)

Yellowknife


G.Finch - RDH 30

Comfort Analysis – Window Surface Temperature & Operative Temperatures (Yellowknife)

SHGC Selection for Comfort

� Optimal SHGC & risk for discomfort depends on

number of factors:

� Window to wall ratio

› Higher window area = greater chance of overheating

� Window orientation

› West-facing windows pose greatest risk to overheating

followed by east- and south-facing

� Potential for shading, type/operation of shading

devices

› Overhangs, shutters, near-by trees or buildings reduce

overheating potential

� If risk of overheating is high then suggest a

lower SHGC window of 0.2 to 0.3 (will pay more

for heating)

� If risk of overheating is low then suggest a

higher SHGC window 0.4 or higher to reduce

heating


G.Finch - RDH 31

Summary: Window Design in Northern Canada

� Window design (amount and orientation) and product

selection has significant impact on energy consumption

& thermal comfort in Northern Homes

� Design a house with reasonable window to wall ratios

(less than 15%), orient glazing primarily to south if

possible and include exterior shading (overhangs,

shutters, trees)

� Ask manufacturers for their product’s U-value & SHGC

� Select the lowest possible U-value available, at least lower

than USI-1.4 (UIP-0.25)

� Assess risk of overheating and choose glazing with

appropriate SHGC

› Low risk choose high SHGC >0.4

› High risk choose lower SHGC 0.15 to 0.3

� rdh.com | buildingsciencelabs.com

Discussion + Questions

[email protected] – 604.873.1181

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