Design Assistance : Step 4

Design Assistance Step 4 : Select a Glass Type

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Glass Performance Values

Glass Performance:

When analyzing and selecting a glass type, it is important to compare the optical and thermal properties of each type of glass and select the one that best matches your specific performance requirements. Glazing is one of the most important factors to consider when designing a skylight. e-skylight.com provides you with several glazing options to choose from. We recommend using only real glass in lieu of translucent, acrylic panels. Glass provides superior thermal and optical properties, won't yellow or fade, and is much less susceptible to leakage after extended exposure to the harsh effects of an outdoor environment.

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Glass Specifications:

1. Standard certification requirements:

A. Float Glass: ASTM C 1036.

B. Heat Treated Glass: ASTM C1048, with surface stress of 5000psi, +/- 1500psi.

C. Laminated Glass: Two lites of equal thickness bonded with a polyvinyl butyral (PVB) interlayer, meeting criteria of ANSI Z97.1-1984 and CPSC 16 CFR 1201 for safety glazing.

D. Insulating Glass: CBA rated by the Insulating Glass Certification Council when tested in accordance with ASTM E 773 and E 774. Dual edge seals with silicone secondary seal. Exterior lite is to be heat strengthened; interior lite to be laminated glass.

2. Performance Requirements:

A. Probability of breakage not to exceed 8/1000 for vertical glass and 1/1000 for sloped glass upon first application of design pressures or due to anticipated thermal stresses.

3. Glazing Unit Description: (Select one)

A. Laminated Glass: two ¼" clear, heat strengthened lites with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer.

B. Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer.

C. Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B) interlayer. A LOF Energy Advantage pyrolytic low-e coating is applied to surface #2 (Coating will be applied to surface #3 with tinted glass).

D. Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer. A PPG Solarban 60 low-e coating is applied to surface #2.

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Types of Glass:

Laminated Glass: Laminated glass consists of two lites of equal thickness (¼") bonded together with a polyvinyl butyral (pvb) interlayer. In the event that the glass should break, the pvb interlayer will allow the glass to remain in the skylight frame. Heat-strengthened glass is twice as strong as regular annealed glass and is used in all e-skylight.com skylights.

Insulated Glass: Insulated glass consists of a ¼" thick, heat-strengthened outer lite, over a ½" dual sealed airspace, over a heat strengthened, laminated inner lite (thickness to be determined based on size of lite). Because of its inherent thermal properties, insulated glass is typically used over a conditioned space, where energy efficiency is of paramount concern.

PPG Solarban 60^TM: Specifically designed for heating dominated climates, PPG Solarban 60^{TM glass reduces heat loss by reflecting heat back into the space, maximizing energy efficiency and reducing heating bills.

PPG Solarban 60^TM: Specifically designed for cooling dominated climates, PPG Solarban 60^TM Solar Control glass reduces unwanted solar heat gain by rejecting a siginifcant portion of the sun's solar infrared energy back to the outside, helping to keep homes cooler and lowering cooling costs in the summer.

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Glazing Energy Terms:
(Please refer to these terms when comparing performance levels)

Visible Light Transmittance: The percentage of visible light that is transmitted through the glass. Interior daylight levels will be determined by this value. The higher the percentage, the more daylight is transmitted.

Solar Transmittance: The percentage of ultraviolet, visible and near infrared energy that is transmitted through the glass.

Visible Light Reflectance: The percentage of light that is reflected from the glass surface.

Solar Reflectance: The percentage of solar energy that is reflected from the glass surface.

ASHRAE U-Value: The amount of heat gain or loss through glass due to the difference between indoor and outdoor temperatures (based upon ASHRAE standard winter nighttime and summer daytime conditions). The colder the climate, and the more expensive the heating fuel, the more important it is to utilize a low U-value glass.

Shading Coefficient: The ratio of solar heat gain through a specific type of glass product to the solar heat gain of a 1/8" (3mm) clear glass. The lower the shading coefficient number, the better the performance of the glass. This is particularly important in warmer climates.

Relative Heat Gain: The amount of heat gain relative to the effects of the solar heat gain (shading coefficient) and conductive heat gain (U-Value) of the glass. The lower the relative heat gain value, the more efficient the glass is in restricting heat gain.

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Performance Values

Product
Transmittance
Reflectance
ASHRAE U-Value
Shading
Coefficient
Solar
Heat Gain Coefficient
Relative Heat Gain

Visible
Solar
Vis-In
Vis-out
Solar
Summer
Winter

Clear Insulated Laminated w/ PPG Solarban 60
69%
32%
12%
12%
28%
0.29
0.29
0.44
0.37
92.06

Clear Insulated Laminated w/ Pyrolytic
Low-e
69%
46%
15%
18%
13%
0.38
0.34
0.76
0.65
158

Clear Insulated Laminated
77%
53%
14%
14%
11%
0.56
0.47
0.78
0.67
163

Clear Laminated
87%
68%
7%
7%
6%
1.00
0.98
0.86
0.74
187

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	A.	Float Glass: ASTM C 1036.
	B.	Heat Treated Glass: ASTM C1048, with surface stress of 5000psi, +/- 1500psi.
	C.	Laminated Glass: Two lites of equal thickness bonded with a polyvinyl butyral (PVB) interlayer, meeting criteria of ANSI Z97.1-1984 and CPSC 16 CFR 1201 for safety glazing.
	D.	Insulating Glass: CBA rated by the Insulating Glass Certification Council when tested in accordance with ASTM E 773 and E 774. Dual edge seals with silicone secondary seal. Exterior lite is to be heat strengthened; interior lite to be laminated glass.

	A.	Laminated Glass: two ¼" clear, heat strengthened lites with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer.
	B.	Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer.
	C.	Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B) interlayer. A LOF Energy Advantage pyrolytic low-e coating is applied to surface #2 (Coating will be applied to surface #3 with tinted glass).
	D.	Insulated laminated glass consisting of a ¼" clear heat strengthened lite, a ½" dual sealed airspace over a laminated lite (thickness to be determined per glass size) with a (.030) (.060) polyvinyl butyral (P.V.B.) interlayer. A PPG Solarban 60 low-e coating is applied to surface #2.

Visible Light Transmittance:	The percentage of visible light that is transmitted through the glass. Interior daylight levels will be determined by this value. The higher the percentage, the more daylight is transmitted.
Solar Transmittance:	The percentage of ultraviolet, visible and near infrared energy that is transmitted through the glass.
Visible Light Reflectance:	The percentage of light that is reflected from the glass surface.
Solar Reflectance:	The percentage of solar energy that is reflected from the glass surface.
ASHRAE U-Value:	The amount of heat gain or loss through glass due to the difference between indoor and outdoor temperatures (based upon ASHRAE standard winter nighttime and summer daytime conditions). The colder the climate, and the more expensive the heating fuel, the more important it is to utilize a low U-value glass.
Shading Coefficient:	The ratio of solar heat gain through a specific type of glass product to the solar heat gain of a 1/8" (3mm) clear glass. The lower the shading coefficient number, the better the performance of the glass. This is particularly important in warmer climates.
Relative Heat Gain:	The amount of heat gain relative to the effects of the solar heat gain (shading coefficient) and conductive heat gain (U-Value) of the glass. The lower the relative heat gain value, the more efficient the glass is in restricting heat gain.

Product	Transmittance		Reflectance			ASHRAE U-Value		Shading Coefficient	Solar Heat Gain Coefficient	Relative Heat Gain
	Visible	Solar	Vis-In	Vis-out	Solar	Summer	Winter
Clear Insulated Laminated w/ PPG Solarban 60	69%	32%	12%	12%	28%	0.29	0.29	0.44	0.37	92.06
Clear Insulated Laminated w/ Pyrolytic Low-e	69%	46%	15%	18%	13%	0.38	0.34	0.76	0.65	158
Clear Insulated Laminated	77%	53%	14%	14%	11%	0.56	0.47	0.78	0.67	163
Clear Laminated	87%	68%	7%	7%	6%	1.00	0.98	0.86	0.74	187