Quick answer: An insulating glass unit (IGU) is two or more glass lites separated by a sealed cavity, with the cavity filled with air or inert gas (argon, krypton). The sealed cavity dramatically reduces heat transfer, achieving U-factor 0.30-0.50 vs 1.10 for single-pane. Required by Florida Energy Code for all conditioned commercial space.
Two glass lites (typically 1/4" each) separated by an aluminum or warm-edge spacer holding them 1/2" apart. The perimeter is sealed with butyl primary sealant + polysulfide or polyurethane secondary sealant. Cavity filled with argon (most common) or air. Common nominal thickness: 1" (1/4" + 1/2" + 1/4").
U-factor: 0.30-0.50 (vs 1.10 single pane). SHGC: 0.20-0.50 (depends on coating). VLT: 35-91% (depends on glass type). Sound transmission loss: STC 28-38 for standard IGUs; higher with laminated lites.
Argon-filled IGUs perform 5-10% better than air-filled on U-factor. Argon is heavier and more viscous, slowing convective heat transfer in the cavity. Most modern commercial IGUs are argon-filled at 90%+ concentration.
Aluminum spacers conduct heat at the IGU edge, creating cold spots. Warm-edge spacers (stainless steel or polymer composite) reduce edge conductivity, improving overall U-factor by 5-15%. Most modern commercial IGUs use warm-edge spacers.
Low-E coating in an IGU goes on surface #2 (outboard glass, inside the cavity) for Florida hot climates. This reflects solar heat before it enters the building. Surface #3 (inboard glass, inside the cavity) is for cold climates.
Standard Florida HVHZ commercial IGU: 1/4" laminated impact tempered (outboard) + 1/2" airspace + 1/4" tempered (inboard) = 1" nominal. This combines: impact rating + safety break + insulation + low-E coating in one assembly.
Properly fabricated and installed commercial IGUs last 20-30 years. Failure mode is seal deterioration allowing moisture vapor into the cavity (visible as fogging or moisture droplets). Warranty typically 10 years against seal failure.
An IGU is two or more glass lites separated by a sealed cavity (typically 1/2" filled with argon or air). The sealed cavity reduces heat transfer dramatically, achieving U-factor 0.30-0.50 vs 1.10 single-pane.
Yes — argon-filled IGUs perform 5-10% better on U-factor than air-filled equivalents. Argon is heavier and slows convective heat transfer in the cavity.
Properly fabricated and installed commercial IGUs last 20-30 years. The failure mode is seal deterioration allowing moisture into the cavity. Warranties typically cover the first 10 years.
Surface #2 (outboard glass, inside the cavity) for Florida hot climates. This reflects solar heat before it enters the building.
Effectively yes. Florida Energy Code requires U-factor ≤ 0.50 (South FL) or ≤ 0.55 (rest of FL) for conditioned commercial space. Single-pane glass cannot meet this; IGUs are the standard solution.
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