What Glass Should You Choose for a Skylight Roof?

【Excellent Optical Performance】

Low-E glass offers high visible-light transmittance—often above 80%, difficult for ordinary glass—while keeping reflectance low. Externally, the appearance is clearer and more transparent, ensuring good daylight while reducing glare pollution from large glass curtain walls and sunrooms.

High solar transmittance alone does not make a material energy-efficient unless heat is retained. Low-E coated insulating glass is a strong energy-saving daylighting material: high solar transmittance, very low U-value, and heat reflected back indoors so temperatures near the glass remain comfortable. Low-E glass also blocks substantial UV, protecting interior finishes from fading.

At equal visible-light transmission, dual-silver and triple-silver Low-E block more solar infrared than single-silver Low-E—lower shading coefficient (SC) and cooler daylight in summer. In winter, indoor warmth must be retained; in summer, outdoor heat must be minimized. Low-E glass meets both demands.

Ordinary glass has visible-light transmittance above 80% with K-value 5.8–6.2 W/m²K (SC ≈ 0.95). Wall K-values around 1.4 W/m²K create uneven heat loss. Modern buildings with large glass areas lose significant energy; developed markets adopted low-emissivity glass early.

At 20°C room temperature, ~90% of infrared on 6 mm glass is absorbed, heating the pane; heat exchange with surroundings transfers much indoor warmth outdoors. Low-E glass reflects infrared and reduces heat loss.

【Energy-Saving Principles】 Insulating glass performance is measured by shading coefficient (SC or SHGC) and U-value.

【Shading Coefficient (SC)】 SC is the ratio of solar heat through the glass versus 5 mm clear glass. Lower SC means less solar heat indoors—preferred in hot climates; higher SC suits cold regions.

【Solar Heat Gain Coefficient (SHGC)】 SHGC compares solar radiation entering through glass versus an open hole of the same size, including direct transmission and re-radiated absorbed heat.

【U-Value】 Lower U-value means better resistance to heat transfer and stronger insulation. Radiation through glass accounts for ~2/3 of window heat loss—low-E coatings significantly reduce U-value.

Dual-silver Low-E insulating glass features:

1. Superior winter insulation, reducing heat loss.
2. Lower shading performance, reducing summer solar heat.
3. High visible-light transmittance for natural daylight.
4. Lower SC, blocking solar infrared especially.
5. Lower U-value, blocking summer outdoor heat while insulating.

Application: Suitable for all regions and building types.

Dual-silver Low-E combines high light transmission with low solar heat gain versus standard Low-E at equal visible transmittance.

Single-silver Low-E (high-transmission type):

1. High visible transmittance—natural, clear daylight.
2. Higher solar heat transmission.
3. Very high far-infrared reflectance—good insulation, low U-value.

Application: Cold northern regions; transparent, daylight-rich facades.

Solar-control Low-E:

1. Moderate visible transmittance, shading strong outdoor light.
2. Lower solar heat transmission.
3. High far-infrared reflectance, limiting secondary heat from outdoor surfaces.

Application: Southern regions and mild northern areas. Winter solar intensity is ~1/3 of summer, so insulation is maintained while summer heat gain is reduced.