Watertightness Performance - One of the Five Key Characteristics of System Windows & Doors

Watertightness Performance

Watertightness refers to the ability of windows and doors to resist rainwater penetration under combined wind and rain conditions when closed.

Key Clarification
Many assume watertightness and airtightness are the same—they are not. Historically, silicone sealant was used for glass installation, but its poor weather resistance led to:

Cracking from thermal expansion/contraction

Hardening over time, causing seal failure

Modern solutions use EPDM gaskets for sealing, but under wind-driven rain, the pumping effect can still force water through micro-gaps between glass and gaskets.

Critical Design Principles
"Drainage Over Blocking" Approach

Multi-channel drainage paths guide infiltrated water out of frames.

Pressure-equalized cavities prevent water backflow into interiors.

Triple Defense System

Primary seal: EPDM gaskets (weather-resistant).

Secondary seal: Structural barriers (e.g., thermal breaks).

Tertiary drainage: Sloped weep holes + capillary breaks.

Installation Precision

Frame-to-wall sealing: Butyl tape + expanding foam.

Sill flashings: Redirect water outward.

Performance Standards
GB/T 7106-2008 Grades: Class 1 (lowest) to Class 6 (highest).

Jiangsu Requirement: Class 4 (withstands ≥350Pa pressure).

Pro Tip: For coastal/high-rise projects, specify:
✔ Class 5-6 watertightness
✔ Dynamic testing (simulating typhoon conditions)
✔ Drainage validation via 15° tilt tests