Using Laminated Glass for Sloped and
Overhead Glazing
Laminated
Glass
Sloped And
Overhead
Glazing
Section 1
OVERVIEW
INTRODUCTION
Using glass in sloped and overhead applications presents numerous design and
safety challenges. If the glass breaks, the glazing system must provide protection
from falling glass. Additionally, an understanding of the unique thermal, solar and
ultraviolet characteristics of sloped and overhead glazing is required to avoid
occupant discomfort and poor energy efficiency, and reduce potential damage to
household furnishings. This Product Application Note is intended to provide an
overview of the range of options that exist to incorporate laminated glass in overhead
and sloped applications.
SLOPED OR OVERHEAD GLAZING
Glass that slopes at an angle of 15° or more from the vertical plane, whether in
sloped walls, overhead glazing, or skylights, is referred to as sloped or overhead
glazing. The possibility of breakage of sloped or overhead glazing is a potential
hazard and, with limited exceptions, building codes require laminated glass or screens
to be used for occupant protection. When properly designed and installed, the
adhesion of the glass to the interlayer means that laminated glass, even when
broken, tends to remain in place, protecting occupants and property from injury and
damage caused by rain, wind, snow, etc.
As is the case with safety glazing, sloped and overhead glazing is regulated. Sloped
and overhead glazing is subjected to potential wind loads, snow loads, live and dead
loads.
Laminated glass packages that incorporate spectrally selective low-E coatings are the
preferred choice for sloped and overhead applications because they not only provide
protection against falling glass, they offer energy efficiency gains as well.
CFP PAN –
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October 2008
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Section 2
USING LAMINATED GLASS IN SLOPED AND OVERHEAD
APPLICATIONS
Laminated
Glass
Sloped And
Overhead
Glazing
CODE COMPLIANCE
Laminated glass with PVB interlayer is recognized by the International Residential
Code (IRC) and specific state and local laws and codes as an acceptable glazing
product for sloped and overhead applications including skylights. The locations,
allowable glazing materials, and standards with which safety glazing must comply are
specified in the IRC, as well as in Consumer Product Safety Commission (CPSC) 16
CFR Part 1201, and American National Standards Institute (ANSI) Z97.1.
In addition to code requirements, the Glazing Industry Code Committee has
established consensus requirements for sloped and overhead glazing. These
standards recognize the safety performance of laminated glass. Unlike monolithic
tempered or heat strengthened (HS) glass, laminated glass does not require the
installation of screens when used in sloped and overhead glazings.
INCORPORATING GUARDIAN RESIDENTIAL LOW-E INTO LAMINATED GLAZING
CONFIGURATIONS
There are two ways to use low-E coatings with laminated glass –either embedded, or
exposed. In this context, embedded refers to a configuration in which the coating(s)
are in direct contact with the PVB interlayer; exposed refers to coatings that are
positioned facing the airspace of an IG unit. Positioning of low-E coated lites within a
laminated glass configuration does not affect safety properties; however there are
thermal and aesthetic implications that should be considered when designing any
laminated glazing package. The thermal performance (U-factor) improvement that is
associated with the use of low-E coatings only applies to laminated configurations in
which the low-E coating is exposed to a sealed airspace. When a low-E coating is
embedded in a laminated configuration, the thermal performance of the configuration
is approximately the same as it would be without a low-E coated lite.
Embedded and exposed coatings both provide the solar control (SHGC) benefit
associated with the low-E coating; however, the resulting SHGC can vary significantly
depending on the glazing configuration. An additional consideration when
determining the preferred positioning of low-E coatings within a glazing system is the
potential for thermal stress. Although typical combinations of glass, PVB, and
Guardian’s Residential Low-E coatings do not result in glass temperatures that are
associated with thermal breakage, thermal and solar simulations should be
performed by a qualified party prior to finalizing configuration design in order to fully
CFP PAN –
Lami Sloped
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October 2008
2
understand the SHGC values and the potential for heat build-up within the glazing
system.
Guidelines for use and positioning of Guardian’s Residential Low-E coated glass in
laminated configurations are provided for reference in Table 1. Note that mock-ups
are advised for aesthetic reasons with some products when they are positioned on
specific surfaces, as these configurations are likely to have more pronounced color
properties.
Laminated
Glass
Sloped And
Overhead
Glazing
Table 1— Guidelines for use and positioning of Guardian’s Residential Low-E coated glass in laminated configurations.
Table 1. Laminated Coated Surface Guide
Illustration Legend
Glass
Coating
Interlayer
Spacer
Annealed or
Temper-Coated
Low-E
Heattreatable
Low-E
Performance Plus II
Yes
No
Yes
Mock-up
Advised
Yes
Mock-up
Advised
Yes
Mock-up
Advised
ClimaGuard 75/68
Yes
No
No
No
Yes
Yes
No
No
ClimaGuard 71/38
Yes
No
Yes
Mock-up
Advised
Yes
Yes
Yes
Mock-up
Advised
ClimaGuard 70/36
Yes
No
Yes
Mock-up
Advised
Yes
Yes
Yes
Mock-up
Advised
ClimaGuard 55/27
Yes
No
Yes
No
Yes
Yes
Yes
No
Performance Plus II HT
No
Yes
Yes
Mock-up
Advised
Yes
Mock-up
Advised
Yes
Mock-up
Advised
ClimaGuard DHT
No
Yes
Yes
No
Yes
Mock-up
Advised
Yes
No
ClimaGuard HT
No
Yes
Yes
Mock-up
Advised
Yes
Yes
Yes
Mock-up
Advised
ClimaGuard 55 HT
No
Yes
Yes
No
Yes
Yes
Yes
No
Coating
Laminated (Monolithic)
Surface
Surface
#3
#2
IGU Lami (Inboard lami lite)
Surface Surface Surface Surface
#2
#3
#4
#5
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THERMAL PERFORMANCE NOTE FOR SLOPED APPLICATIONS
Center of glass values based on vertical installation are commonly used for simple
comparison; however, U-factors for sloped glazing vary from vertical. Figure 1 and
Figure 2 illustrate how U-Factor degrades as the installation slope is varied from
vertical (90°) to horizontal (0°). This data indicates that a slower rate of heat transfer
occurs in vertical glazing than in sloped glazing. In skylights, as the slope of the
skylight becomes more horizontal, the rate of heat transfer through the glazing
increases. If the same glass is used in a vertically-glazed application and in a sloped
application, in the winter, the sloped-glazed application will lose heat more quickly
than the vertically-glazed application.
Laminated
Glass
Sloped And
Overhead
Glazing
Figure 1—Depiction of U-factor as a function of installed slope angle for 7/8” OA laminated glass solar-control IGU
(lami inboard with ClimaGuard 55/27 low-E #2).
U-f actor vs. Installed Slope Angle
ClimaGuard 55/27 #2 Surface
0.40
0.35
U-Factor
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
15
30
45
Slope (degrees)
60
75
90
Figure 2. Illustration of center of glass U-factor for identically configured glazing packages in sloped and vertically
glazed applications.
U-Factor: 0.331
30°
U-Factor: 0.235
90°
CFP PAN –
Lami Sloped
Overhead
Glazing
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October 2008
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Section 3
ADDITIONAL RESOURCES
SELECT LAMINATED GLAZING STANDARDS
…
CPSC 16 CFR 1201 Safety Standard for Architectural Glazing Materials
…
ANSI Z97.1 American National Standard for Safety Glazing Materials Used in
Buildings – Safety Performance Specifications and Methods of Test
…
CAN/CGSB-12.1 Tempered or Laminated Safety Glass
…
ASTM C1172 Standard Specification for Laminated Architectural Flat Glass
Laminated
Glass
Sloped And
Overhead
Glazing
ADDITIONAL GUARDIAN LAMINATED GLASS PRODUCT APPLICATION NOTES
Using Laminated Glass for Solar Control and Energy Management in
Residential Applications – CFP PAN Lami Solar control and Energy Management.
…
Using Laminated Glass for Sound Control in Residential Applications – CFP PAN
Lami Sound Control.
…
Using Laminated Glass for Hurricane-Impact and Windborne Debris-Resistant
Applications – CFP PAN Lami Hurricane and Windborne Debris
…
Using Laminated Glass for Safety and Burglary-Resistance in Residential
Applications – CFP PAN Lami Safety and Burglary-Resistance.
…
CFP PAN –
Lami Sloped
Overhead
Glazing
and Skylights
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October 2008
5
LAMINATED AND COATED GLAZING INSPECTION AND QUALITY STANDARDS
Table 2. ASTM C1172-03 – Maximum Allowable Laminating Process Blemishes
ASTM C1172-03 - Maximum Allowable Laminating Process Blemishes: Inches (mm)
Up to 25 ft.2 (2.5m2)
Central
Outer
Blemish
Boil
(bubble)
Blow-in;
edge boil
Fuse
Hair, lint
(single strand)
Inside dirt
(dirt spot)
Lint - areas of
concentrated lint
Separation,
discoloration
Short Interlayer;
unlaminated area chip
Interlayer scuff;
streak
25 - 75 ft.2 (2.5 - 7.0m2)
Central
Outer
1/16 (1.6)
3/32 (2.4)
1/8 (3.2)
3/16 (4.8)
1/4 (6.4)
1/4 (6.4)
n/a
CE: 1/4 (6.4)
EE: 1/32 (0.8)
n/a
CE: 1/4 (6.4)
EE: 1/16 (1.6)
n/a
CE: 5/16 (8.0)
EE: 3/32 (2.4)
1/32 (0.8)
1/16 (1.6)
1/16 (1.6)
3/32 (2.4)
3/32 (2.4)
5/32 (4.0)
light
intensity
medium
intensity
light
intensity
medium
intensity
medium
intensity
medium
intensity
1/16 (1.6)
3/32 (2.4)
3/32 (2.4)
5/32 (4.0)
1/8 (3.2)
3/16 (4.8)
light
intensity
light
intensity
light
intensity
light
intensity
light
intensity
light
intensity
none
none
none
none
none
none
n/a
light
intensity
CE: 1/4 (6.4)
EE: 1/16 (1.6)
light
intensity
n/a
light
intensity
Laminated
Glass
Sloped And
Overhead
Glazing
Over 75 ft.2 (7.0 m2)
Central
Outer
CE: 1/4 (6.4)
EE: 3/32 (2.4)
light
intensity
n/a
light
intensity
CE: 1/4 (6.4)
EE: 1/4 (6.4)
light
intensity
Notes:
1. Inspection must be performed with the glazing system in a vertical orientation.
2. Central Area is defined by an oval / circle, whose axis, when centered, is <80% of the overall dimension.
3. Outer Area is defined as the area outside of the central area.
4. CE: covered edge of glass edge bite.
5. EE: exposed edge (if CE or EE is unknown, use CE tolerance).
6. Light Intensity: barely noticeable at 36 inches (914.4 mm).
7. Medium Intensity: noticeable at 36 inches (914.4 mm) but not at 11 feet (3,352.8mm).
8. All imperfections noted should be separated by a minium of 12 inches (305mm).
Table 3. ASTM C1376-03 – Quality Specifications for Coated Overhead Glass
ASTM C1376-03 - Quality Specifications For Coated Overhead Glass
Blemish
Central Area
Outer Area
Pinhole
3/32" (2.4mm) Max.
1/8" (3.2mm) Max.
Spot
3/32" (2.4mm) Max.
1/8" (3.2mm) Max.
Coating Scratch
3" (75mm) max length
4" (100mm) max length
Mark / Contaminant
3" (75mm) max length
length + width not to exceed
3/4" (19mm)
None allowed
4" (100mm) max length
length + width not to exceed
3/4" (19mm)
None allowed
Coating Rub
Crazing
Corrosion
None Allowed
None allowed
Notes:
1. These specifications apply to cut size glass only. For specifications of stock size glass contact the
manufacturer.
2. The glass shall be inspected, in transmission, at a distance of 15 ft.(3m) at a viewing angle of 90
degrees to the specimen against a bright uniform background. If a blemish is readily apparent under
these viewing conditions, the above criteria applies.
3. Central Area is defined by a square / rectangle, defined by the center 80% of the length and 80% of
the width dimensions centered on a lite of glass.
4. Outer Area is defined as the area outside of the central area
5. No more than two readily apparent blemishes are allowed in a 3-in. (75mm) diameter circle, and no
more than five readily apparent blemishes are allowed in a 12-in. (300mm) diameter circle.
CFP PAN –
Lami Sloped
Overhead
Glazing
and Skylights
Edition 2.1
October 2008
6
PERFORMANCE AND COMPLIANCE OF LOW-E ENHANCED LAMINATED GLASS
CONFIGURATIONS (REFERENCE TABLE NOTES ON THE FOLLOWING PAGE)
Table 4. Performance and Compliance of Low-E Enhanced Laminated Glass Configurations
Table 4. Performance and Compliance of Low-E Enhanced Laminated Glass Configurations
ASTM
Configuration
CPSC CPSC F1233 UL
Cat. I Cat. II Class 1 972 STC OITC
Monolithic Clear Glass [1/8"]
27
24
Uncoated 1/8" annealed glass
Uncoated
U+Factor
T vis
% Tuv%
SHGC
Air
Argon
Hurricane
Small
Large
Missile Missile
90%
74%
0.87
1.00
n/a
+
+
-
-
27
24
90%
74%
0.87
1.00
n/a
-
-
Lami glass - 2.7mm
[0.030" PVB]
Lami glass - 2.7mm
+
+
-
-
34
30
89%
0%
0.81
1.00
n/a
-
-
+
+
-
-
34
30
89%
0%
0.80
1.00
n/a
-
-
1/8" glass
[0.030" PVB]
1/8" glass
n/a
+
+
n/a
+
+
n/a
n/a
n/a
70%
69%
n/a
0%
0%
n/a
0.41
0.38
n/a
1.00
1.00
n/a
n/a
n/a
n/a
+
+
+
+
-
n/a
30
30
n/a
-
n/a
34
34
+
+
34
35
30
31
59%
88%
0%
0%
0.33
0.79
1.00
0.98
n/a
n/a
+
-
n/a
+
+
n/a
+
+
n/a
+
+
n/a
+
+
n/a
35
35
n/a
31
31
n/a
70%
69%
n/a
0%
0%
n/a
0.40
0.38
n/a
0.98
0.98
n/a
n/a
n/a
n/a
+
+
+
+
+
+
+
+
+
+
35
35
31
32
58%
88%
0%
0%
0.33
0.78
0.98
0.96
n/a
n/a
+
+
+
n/a
+
+
n/a
+
+
n/a
+
+
n/a
+
+
n/a
35
35
n/a
32
32
n/a
70%
68%
n/a
0%
0%
n/a
0.40
0.37
n/a
0.96
0.96
n/a
n/a
n/a
n/a
+
+
n/a
+
+
+
+
+
+
35
32
58%
0%
0.33
0.96
n/a
+
+
-
-
-
-
31
26
82%
59%
0.78
0.48
n/a
31
31
26
26
75%
71%
46%
24%
0.69
0.39
0.32
0.29
0.27
0.24
31
31
31
26
26
26
70%
55%
82%
30%
18%
59%
0.36
0.27
0.78
0.29
0.29
0.48
0.24
0.24
n/a
31
31
26
26
75%
71%
46%
24%
0.69
0.39
0.318
0.29
0.27
0.24
31
31
26
26
70%
55%
30%
18%
0.36
0.27
0.293
0.289
0.24
0.24
-
-
-
-
37
31
81%
0%
0.75
0.47
n/a
37
37
37
31
31
31
75%
70%
68%
0%
0%
0%
0.67
0.39
0.36
0.314
0.287
0.29
0.27
0.24
0.24
-
-
1/8" tempered glass
Laminated
Glass
Sloped And
Overhead
Glazing
Monolithic Laminated Glass [5/16"]
Uncoated
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
ClimaGuard 55/27 #2
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
1/8" glass
[0.060" PVB]
1/8" glass
ClimaGuard 55/27 #2
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
1/8" glass
[0.090" PVB]
1/8" glass
ClimaGuard 55/27 #2
n/a
-
Standard Insulating Glass Unit [3/4"]
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
ClimaGuard 55/27 #2
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
ClimaGuard 55/27 #2
1/8" annealed glass
[1/2" AS]
1/8" annealed glass
1/8" tempered glass
[1/2" AS]
1/8" tempered glass
+
+
+
+
+
+
+
+
+
+
Laminated Insulating Glass Units (3/4" OA, Laminated Glass Inboard)
Uncoated
+
+
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
1/8 glass
[1/2" AS ]
1/4" Lami (0.030")
ClimaGuard 55/27 #2
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
1/8 glass
[1/2" AS ]
1/4" Lami (0.060")
ClimaGuard 55/27 #2
Uncoated
ClimaGuard 75/68 #3
ClimaGuard 71/38 #2
ClimaGuard 70/36 #2
ClimaGuard 55/27 #2
1/8 glass
[1/2" AS ]
1/4" Lami (0.090")
+
+
+
+
+
+
+
+
+
+
+
+
37
37
31
31
54%
80%
0%
0%
0.27
0.75
0.285
0.466
0.24
n/a
+
+
+
+
+
+
+
+
+
+
+
+
+
+
37
37
37
31
31
31
74%
69%
68%
0%
0%
0%
0.67
0.38
0.36
0.311
0.285
0.288
0.27
0.24
0.24
+
+
+
+
+
+
+
+
+
+
+
+
+
+
37
31
37* 31*
53%
80%
0%
0%
0.27
0.74
0.281
0.462
0.23
n/a
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
37* 31*
37* 31*
37* 31*
74%
69%
68%
0%
0%
0%
0.67
0.38
0.36
0.309
0.283
0.285
0.26
0.23
0.24
+
+
+
+
+
+
+
+
+
+
37* 31*
53%
0%
0.27
0.281
0.23
+
+
CFP PAN –
Lami Sloped
Overhead
Glazing
and Skylights
Edition 2.1
October 2008
7
LAMINATED GLASS CONFIGURATION TABLE NOTES
… The information contained in this table is based on center-of-glass
performance based on vertical installation. Total window system simulation and
testing is necessary to determine window system performance and compliance.
Laminated
Glass
Sloped And
Overhead
Glazing
Accurate thermal performance modeling must include the anticipated
installation angle.
…
– Indicates that the composition may not meet requirements of the test
standard when annealed glass is used.
…
… + Indicates that the composition may provide the level of protection shown with
correct installation and framing.
… Information regarding CPSC Cat. I and II, ASTM F-1233 Cat.1, and UL 972 is
included in Section 3.
… Sound Transmission Class (STC): Expressed in laboratory-measured dB,
indicating the level of sound insulation of interior construction material.
… Outdoor-Indoor Transmission Class (OITC): Expressed in laboratory-measured
dB, indicating the acoustic performances of exterior doors and windows.
GUARDIAN MANUFACTURES LAMINATED GLASS IN THE FOLLOWING LOCATIONS
…
Guardian Galax
110 Jack Guynn Drive, Galax, VA 24333
Phone: (276) 236-5196
…
Guardian Reedley
1485 East Curtis Ave., Reedley, CA 93654
Phone: (559) 638-3588
…
Guardian Rexdale
355 Attwell Drive, Rexdale, Ontario, Canada M9W 5C2
Phone: (416) 674-6945
For additional information regarding storage, handling, fabrication, Limited Warranty coverage
or use of any Guardian glass product, please contact the Guardian Customer Engineering
Group at 888-521-9734
CFP PAN –
Lami Sloped
Overhead
Glazing
and Skylights
Edition 2.1
October 2008
8