The most common façade and window specification starts with a 5 mm + 18 mm cavity + 5 mm insulating glass unit (IGU). Replacing the air cavity with argon (5+18Ar+5) improves thermal performance by roughly 10–15 %.
Cavity width matters. Thermal insulation peaks around 12 mm and remains largely flat through 16 mm, while acoustic performance sees diminishing returns beyond 16 mm. Spacers wider than 20 mm are generally not recommended—they increase deformation risk, can reduce thermal performance, and add cost without proportional benefit.
For harsh climates and heavy noise, a triple-glazed two-cavity unit (5+12A+5+12A+5) delivers around 35–40 % better thermal performance and 4–6 dB additional sound reduction compared with an argon-filled double unit. In high-rise residential or elevated-road applications—especially in warmer regions—a laminated IGU such as 5+16A+5+0.76 mm PVB+5 is often preferable. The PVB interlayer retains glass fragments after breakage, blocks approximately 99 % of UV radiation, and outperforms triple glazing on mid-to-low frequency noise. A 0.76 mm interlayer suits typical residential use near elevated roads; specify 1.14 mm for façades facing main traffic arteries. Interlayer thickness should be matched to glass thickness and acoustic load.
A Low-E coating reflects long-wave interior heat in winter and solar infrared in summer, improving overall thermal performance by up to 50 %. On otherwise identical units, Low-E glass can lower the U-value by 35–42 % and the solar heat gain coefficient (SHGC) by 20–43 %, while increasing infrared blocking by a factor of 8–10. The benefit is amplified when the cavity is argon-filled.