Glass, Glazing and Glass, Glazing and Window Energy PerformanceWindow Energy Performance
by Alex McGowan, P.Eng.by Alex McGowan, P.Eng.Levelton Consultants LimitedLevelton Consultants Limited
Victoria, British Columbia, CanadaVictoria, British Columbia, Canada
AIBC Module V “Skin Problems”AIBC Module V “Skin Problems”April 26, 2007April 26, 2007April 26, 2007April 26, 2007
Outline of PresentationOutline of Presentation
�� Physics Review Physics Review -- RadiationRadiation
�� Glazing Performance IndicesGlazing Performance Indices
�� Glazing OptionsGlazing Options�� Glazing OptionsGlazing Options
�� Implications of Glazing SelectionImplications of Glazing Selection
�� Energy RatingEnergy Rating
Physics Review: RadiationPhysics Review: Radiation
UV����VIBGYOR���� infra-red
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Radiation passing through glazingRadiation passing through glazing
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
Glass CharacteristicsGlass Characteristics
ε2 ε3
ρρρρ1 αααα1
ττττv
Glazing System CharacteristicsGlazing System Characteristics
OUT Glazing #1 Glazing #2 I�
U-factor = rate of heat loss per unit area per unit δT
W/m2-ºC or BTU/hr-ft2-ºF
A
B
Visible Transmittance (VT or τv) =
similar to SHGC, but in visible spectrum)
Solar Heat Gain Coefficient (SHGC) =
fraction of incident solar
that arrives at the interior
(= B/A in solar spectrum)
Glazing OptionsGlazing Options
�� reflective coatingsreflective coatings
�� lowlow--emissivity coatingsemissivity coatings
�� spectrally selective glassspectrally selective glass
�� heatheat--absorbing glassabsorbing glass�� heatheat--absorbing glassabsorbing glass
�� multiple glazingsmultiple glazings
�� gas fillsgas fills
�� heatheat--treated glasstreated glass
�� lowlow--conductivity spacersconductivity spacers
Reflective coatingsReflective coatings
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
(increase reflectivity of surface)
Reflective GlassReflective Glass
�� metal or metalmetal or metal--oxide oxide
�� silver, copper, gold, earthsilver, copper, gold, earth
�� high internal gainshigh internal gains
�� large cooling loadlarge cooling load
�� lower solar gainslower solar gains
�� increased comfortincreased comfort�� increased comfortincreased comfort
�� lower visible transmittancelower visible transmittance
�� dramatic façadedramatic façade
�� coating #1 = mirrorcoating #1 = mirror
�� coating #2 = tintcoating #2 = tint
�� coating #3/#4 = mistakecoating #3/#4 = mistake
Tinted GlassTinted Glass
�� colouring agents colouring agents addedadded
�� absorbs energyabsorbs energy
�� bronze, grey, green, bronze, grey, green, blueblueblueblue
�� warmer glasswarmer glass
�� breakage a concernbreakage a concern
�� edge cuts are keyedge cuts are key
�� lower visible lower visible transmittancetransmittance
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
LowLow--emissivity Coatingsemissivity Coatings
(Emissivity of glazing)
(Reflectivity of glazing)
LowLow--emissivity coatingsemissivity coatings
OUT Glazing #1 Glazing #2 I�
#1 #2 #3 #4
(Infrared Emissivity
of glazing)
Pyrolitic coatingsPyrolitic coatings
� metallic oxides applied during the float
� commonly called “hard” coats
� AFG Comfort E2™ (ε = 0.20) and Stopsol™
� Pilkington Energy Advantage (ε = 0.16)
� PPG Sungate 500 (ε = 0.21)� PPG Sungate 500 (ε = 0.21)
� more durable during assembly and storage
� can be heat-treated and laminated
� no need for edge deletion
� can be used monolithically (not recommended)
� reflective coatings can be on #1 surface — not recommended
Sputter coatingsSputter coatings
� bombardment of metal or metal-oxide atoms
� aka vapour deposition, or “soft” coat
� specific metal used determines performance
� AFG Comfort Ti™ (ε = 0.03 - 0.04)
� PPG Solarban 60 (ε = 0.035)
� PPG Sungate 100 (ε = 0.09)
� Cardinal Lo-e2 (ε = 0.04) or Lo-e3 (ε = 0.05)
� less durable than pyrolitic coatings
� typically lower U-factor, lower transmittance
� can be applied to any glass substrate
� some now becoming post-temperable
no low-e detected
low-e on other side of near glass
low-e on one side of far glass
all lit = low-e on contact surface
The Envelope, Please: Transmission LossesThe Envelope, Please: Transmission Losses
• U-factor is measured in W/m2-°C, or in BTU/hr-ft2°F
• R is reciprocal of U, so it’s m2-°C/W, or hr-ft2°F/BTU
• Determined by hot-box measurement (SCC accredited lab)
or computer model (FRAME/VISIO�, THERM/WI�DOW)
• Typical values:
3½” glass-fibre batt R12 (RSI 2.1) Double-glazing, clear U2.81
RRRRRSI
3½” glass-fibre batt R12 (RSI 2.1) Double-glazing, clear U2.81
Nom 2x4 stud wall R7 (RSI 1.2) Double, hard low-e on #2 U1.79
Above with 1” XPS R12.5 (RSI 2.2) Double, hard low-e on #3 U1.79
5½” glass-fibre batt R19 (RSI 3.4) Triple, hard low-e on 2/5 U1.07
Nom 2x6 stud wall R13 (RSI 2.3) Double, soft low-e on #2 U1.74
Above with 1” XPS R18.5 (RSI 3.3) Above in vinyl frame U1.87
The Envelope, Please: Solar GainsThe Envelope, Please: Solar Gains
• SHGC determined by direct measurement (�STF), or by
computer model (VISIO� in Canada, WI�DOW in the US)
• number of glazing layers
• presence of tints or coatings
• type of coating (pyrolitic or vapour-deposition)
• surface on which coating is applied (#2 or #3)
• shading (intentional, self-shading, adjacent buildings)• shading (intentional, self-shading, adjacent buildings)
• amount of glazed area and orientation
Typical values:
Single glazing 0.86 Double, hard low-e on #2 0.65
Double glazing 0.76 Double, hard low-e on #3 0.71
Triple glazing 0.69 Double, soft low-e on #2 0.42
Double reflective 0.17 Triple, soft low-e on #2 & #5 0.35
LowLow--emissivity Coatings emissivity Coatings –– triplestriples
OUT Glazing Glazing Glazing I�
#1 #2 #3
#1 #2 #3 #4 #5 #6
LowLow--emissivity Coatings emissivity Coatings –– triplestriples
OUT Glazing Glazing Glazing I�
#1 #2 #3
#1 #2 #3 #4 #5 #6
LowLow--emissivity Coatings emissivity Coatings –– triplestriples
OUT Glazing Glazing Glazing I�
#1 #2 #3
#1 #2 #3 #4 #5 #6
LowLow--emissivity Coatings emissivity Coatings –– quadsquads
OUT Glazing Glazing Glazing Glazing I�
#1 #2 #3 #4
#1 #2 #3 #4 #5 #6 #7 #8
Gas FillsGas Fills
� most common gas fill: air
� also argon, krypton, SF6
� several fill methods: timer, sniffer, batch
� lower U-factor (~5% clr; ~10% low-e)
� no effect on SHGC or visible
� problem: long-term diffusion (argon)
� problem: glass deflection
� problem: invisible
Warmer Glass = Thermal ComfortWarmer Glass = Thermal Comfort
� reduced condensation potential
� induced draft
� radiant loss� radiant loss
� asymmetric radiant loss
� ���� discomfort
� So what ?
The Energy RatingThe Energy Rating
� Defined in CSA A440.2, revised in 2004
� ER = [57.76 * SHGC] - [21.9 * U] - [0.54 * L75 /Aw] + 40
= [solar gains] – [transmission losses] – [leakage losses]
Typical values (vinyl casement, insulating spacer, A3 rating):
SHGC U old ER new ERSHGC U old ER new ER
Clear double-glazed 0.55 2.44 -15 +17
Pyrolitic low-e/argon 0.52 1.73 -1.8 +30.7
Sputter low-e/argon 0.47 1.58 -2.1 +31.1
Low-e2/argon 0.30 1.52 -13.1 +23
Typical R28 wall 0.001 0.20 -4.3 +35
Energy StarEnergy StarTMTM
Energy StarEnergy StarTMTM windows windows
� Zone A (HDD < 3500): U < 2.0 (0.35) OR
ER > (17 sash, 27 no sash)
� Zone B (HDD between 3500 and 5500): U < 1.80 (0.32) OR ER > (21 sash, 31 no sash)
Zone C (HDD between 5500 and 8000): U < 1.60 (0.28) OR � Zone C (HDD between 5500 and 8000): U < 1.60 (0.28) OR ER > (25 sash, 35 no sash)
� For a list of rated windows, go to
http://oee.nrcan.gc.ca/energystar/ ORhttp://www.bchydro.com
Questions | Comments |
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Glass, Glazing and Glass, Glazing and Window Energy Performance
AIBC Module V “Skin Problems”AIBC Module V “Skin Problems”April 26, 2007April 26, 2007