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Glass selection is single most important decision in aluminum sunroom project.
Wrong glass choice cause problem that is very difficult and expensive to fix after installation. Too much heat gain make sunroom unusable in summer. Too much heat loss make it cold in winter. Condensation problem cause water damage. Poor UV control cause furniture and flooring to fade. Getting glass right from beginning save you much trouble and cost later.
Single Pane Glass is cheapest option but only suitable for garden shed or storage type application. It provide no thermal insulation, condense heavily in cold weather on inside surface, and offer no meaningful protection from temperature extreme. For any sunroom where you plan to spend time, single pane glass is not acceptable choice.
Standard Double Pane Insulating Glass Unit (IGU) is minimum specification for three season sunroom.
It consist of two glass layer separated by aluminum or warm edge spacer filled with dry air or argon gas. Typical configuration is 5mm glass plus 12mm gap plus 5mm glass, written as 5+12A+5. This provide basic thermal insulation with U-value around 2.8 to 3.2 W/m²K. Adequate for mild climate but still allow significant heat gain in summer and heat loss in winter.
Low-E Double Pane Glass is significant upgrade and strongly recommend for any four season sunroom application. Low-E stand for low emissivity. It refer to microscopic metallic coating apply to glass surface that reflect infrared heat radiation while allowing visible light to pass through. Effect of Low-E coating is dramatic. In summer, it reflect solar heat radiation outward, preventing excessive heat buildup inside sunroom. In winter, it reflect interior heat back inside, reducing heat loss through glass.
Low-E glass come in different types for different climate. Solar control Low-E with low SHGC value around 0.25 to 0.35 is best for hot climate where cooling is main concern. It block lot of solar heat while still allowing good natural light. Passive Low-E with higher SHGC around 0.4 to 0.55 is better for cold climate where you want to benefit from solar heat gain in winter while still reducing summer overheating. U-value for Low-E double pane glass typically range from 1.4 to 1.8 W/m²K, significantly better than standard double pane.
Argon Gas Fill is upgrade that work well together with Low-E coating.
Argon is inert gas that is denser than air. When argon replace air in gap between glass pane, it conduct heat less efficiently than air. This improve U-value of glass unit by 10 to 15 percent compared to air fill unit with same glass. Argon fill combine with Low-E coating is standard specification for quality four season sunroom glass. Together they can achieve U-value of 1.2 to 1.6 W/m²K.
Laminated Safety Glass is essential for sunroom roof panel application. When glass is overhead, safety become critical concern. If normal tempered glass break, it shatter into small pieces that fall down on person below. Laminated glass have PVB or SGP interlayer that hold broken glass pieces together even when broken. Glass may crack but it stay in one piece and does not rain down. This is not optional feature for roof glass in any serious sunroom design. It is matter of safety. Most building code in developed country require laminated or specific safety glass for overhead glazing. Zcsung use laminated safety glass as standard for all sunroom roof panel for this reason.
Triple Pane Glass offer highest thermal performance available.
Three glass layer with two gas filled gap can achieve U-value of 0.6 to 1.0 W/m²K. This is passive house level performance. Triple pane glass is heavy and cost more than double pane, but for four season sunroom in very cold climate like Canada, Scandinavia or northern China, it make indoor environment comfortable without expensive heating system working too hard. Zcsung offer triple pane option for project in extreme cold climate where maximum thermal performance is necessary.