Thermal performance core parameter: heat transfer coefficient (K value) — the lower the better. In cold northern regions K ≤ 1.8 W/(m²·K) is recommended, paired with triple glazing (e.g. 5 mm + 12A argon + 5 mm + 12A argon + 5 mm) and a multi-chamber thermal-break profile (PA66 strip ≥ 24 mm wide). Warm-edge spacers: aluminium spacers conduct heat easily; system windows mostly use TPE or stainless warm-edge spacers to reduce edge heat loss. Sound insulation core parameter: sound reduction (dB) — homes by busy roads need ≥ 35 dB, with laminated insulating glass (e.g. 5 mm + PVB + 5 mm + 20A argon + 5 mm) plus four sealing strips (ordinary windows usually have two). Resonance frequency: system windows avoid resonance through differing glass thicknesses (e.g. 5 mm + 6 mm); ordinary windows with uniform thickness easily resonate with low-frequency noise such as engine rumble.