Quick answer: Low-E (low-emissivity) glass uses microscopic metallic coatings to reduce heat transfer through the window. In Florida's hot climate, the goal is to keep solar heat OUT — which means a low Solar Heat Gain Coefficient (SHGC). The Florida Energy Code requires SHGC ≤ 0.25 for most commercial fenestration in Climate Zone 1 (South Florida). Low-E coatings are applied on surface #2 (outboard of cavity) for solar control or surface #3 (inboard of cavity) for heating climates — Florida wants #2.
Low-E coatings are microscopically thin layers of metal oxides (typically silver, tin, or zinc) applied to one surface of a glass lite. They reflect infrared (heat) radiation while allowing visible light to pass. The result: a window that lets light in but keeps heat out.
In an insulated glass unit (IGU), surfaces are numbered 1-4 from outside to inside. Surface #2 (outboard glass, inside the cavity) is the standard low-E position for hot climates like Florida — it reflects solar heat before it enters the building. Surface #3 (inboard glass, inside the cavity) is for cold climates where the goal is to keep interior heat in.
U-factor: heat transfer rate (lower is better in Florida). Typical low-E commercial glass: 0.28-0.45. Solar Heat Gain Coefficient (SHGC): fraction of solar radiation that enters (lower is better in Florida). Typical low-E commercial glass: 0.20-0.35. Visible Light Transmittance (VLT): fraction of visible light (higher is generally preferred). Typical low-E: 35-70%.
FBC Energy Conservation chapter for commercial buildings in Climate Zone 1 (South Florida) requires SHGC ≤ 0.25 for vertical fenestration and U-factor ≤ 0.50. Climate Zone 2 (rest of Florida) is slightly less strict. Most commercial buildings default to a high-performance low-E that easily exceeds these minimums.
Solarban 60, Solarban 70XL, Solarban 90 (Vitro). SunGuard SuperNeutral 68, SunGuard HP Neutral 41 (Guardian). VRE-46, VRE-67 (Viracon). Each has slightly different VLT and SHGC. Architects often spec specific products by name; glaziers source through approved fabricators.
Low-E coating adds roughly 8-15% to the glass line item. The energy savings typically pay back the premium in 3-6 years on conditioned commercial space.
Low-E (low-emissivity) glass has a microscopic metal oxide coating that reflects infrared heat while allowing visible light to pass. In Florida's hot climate, low-E glass reduces cooling loads by keeping solar heat out of the building.
Surface #2 (the outboard glass, inside the cavity) is the standard position for hot climates like Florida. This position reflects solar heat before it enters the building.
Florida Energy Code requires a maximum SHGC of 0.25 for most commercial vertical fenestration in South Florida. Low-E coatings are the standard way to meet this requirement, though other compliance paths exist.
Solarban 70XL has lower SHGC (better solar heat rejection) than Solarban 60, with slightly less VLT. 70XL is more commonly specified for South Florida high-performance commercial buildings.
Slightly. Some low-E coatings have a faint blue, green, or silvery tint. High-performance low-E products often have nearly neutral appearance. Architects typically review actual glass samples before spec.
ACG · CGC #1531993 · 48-hour bid turnaround on commercial plans.
Send Us Plans