How are aluminum windows distinguished by energy efficiency rating?

2025,10,28

The energy efficiency rating of Aluminum Windows is primarily determined through a comprehensive assessment of core indicators such as heat transfer coefficient, airtightness, watertightness, thermal insulation, and sound insulation. Different countries and regions have differentiated grading standards based on their climate characteristics.

International Standards: ISO and European Standards

The International Organization for Standardization (ISO) and the European Standard for Windows and Doors (EN) classify aluminum window energy efficiency into seven grades, from A to G, with Grade A being the most efficient. The thermal transfer coefficient (U-value) is a key indicator, representing the amount of heat transferred per unit area of the window per unit temperature difference, expressed in W/(m2·K). Grade A aluminum windows must have a U-value ≤1.1, indicating excellent insulation performance, significantly reducing winter heating energy consumption. Grade G windows have a U-value ≥5.0, indicating poor insulation performance and are suitable for temperate climates. Furthermore, airtightness is graded based on air permeability per unit area (q² value). Grade A aluminum windows have a q² value ≤1.5 m³/(m2·h), effectively preventing indoor and outdoor air convection, reducing air conditioning or heating loads.

How Do Aluminum and Vinyl Windows Compare in Energy Efficiency

Chinese Standards: GB/T and Building Energy Conservation Code

The current Chinese standards, "Classification and Testing Methods for Airtightness, Watertightness, and Wind Pressure Resistance of Exterior Doors and Windows of Buildings" (GB/T 7106-2019) and "Energy-Efficiency Performance Labeling for Building Doors and Windows," rank aluminum window energy efficiency levels from 1 to 10, with Level 1 being the best. Specific indicators include:

Heat transfer coefficient (K value): Level 1 aluminum windows have a K value of ≤1.1 W/(m2·K), while Level 10 has a K value of ≥5.0 W/(m2·K). For example, in Beijing, where winters are cold, aluminum windows with a K value of ≤1.8 are recommended to reduce heating energy consumption.

Airtightness: Level 1 aluminum windows have an air permeability per unit seam length (q1 value) of ≤0.5 m³/(m2·h), while Level 8 has a q1 value of ≤4.0 m³/(m2·h). Shanghai's summers are humid, and poorly airtight aluminum windows can easily cause cold air to leak out, increasing the air conditioning load.

Watertightness: Grade 6 aluminum windows can withstand water pressures of 700 Pa or higher, making them suitable for typhoon-prone areas such as Guangdong, preventing rainwater leakage and damage to interior finishes.

Insulation: Grade 10 aluminum windows have a K value of 5.0 W/(m2·K) or higher, making them suitable for temperate regions like Yunnan; Grade 1 aluminum windows are suitable for colder regions like Heilongjiang.

US Energy Star Certification: Climate Zoning Adaptation

The Energy Star certification, jointly developed by the U.S. Department of Energy (DOE) and the Environmental Protection Agency (EPA), divides the United States into four regions based on climate differences:

Northern Region (primarily heating): Aluminum windows must have a U-value ≤ 1.20 W/(m2·K) and a Solar Heat Gain Coefficient (SHGC) ≥ 0.35 to reduce winter heating energy consumption. For example, Minnesota requires aluminum windows with a U-value ≤ 1.0.

Southern Region (primarily cooling): A SHGC ≤ 0.25 is required to block summer solar heat. In Florida, aluminum windows with a SHGC ≤ 0.20 should be selected, along with low-E glass for improved energy efficiency.

Central climate zones: Balancing heating and cooling needs is essential, with a U-value ≤ 1.40 and a SHGC ≤ 0.30.

Selection Recommendation: Match performance to local conditions.

Severely cold regions: Prefer aluminum windows with a Class 1 thermal conductivity (K value ≤ 1.1) and Class 1 airtightness (q1 value ≤ 0.5). For example, in Inner Mongolia, triple-glazed, two-chamber insulated glass aluminum windows are recommended.

Hot regions: Choose aluminum windows with a SHGC ≤ 0.25. For example, in Xinjiang, aluminum windows coated with Low-E film can reflect solar heat radiation.

Rainy regions: Ensure watertightness of Class 6 (ΔP ≥ 700 Pa). For example, in Zhejiang, aluminum windows with drainage holes should be selected.

Noisy environments: Aluminum windows with a sound insulation performance of Class 6 (Rw + Ctr ≥ 45 dB) are suitable for areas near airports or in busy commercial districts.

With over 15 years of experience, Dongguan Wendou Windows & Doors Co., Ltd. is one of China's leading aluminum window and door manufacturers. With professional designers, an independent R&D team, and dedicated sales and technical teams, we offer a one-stop service, providing expert design solutions and comprehensive technical support. Whether you require standard sizes or custom windows and doors, we can provide professional solutions for your residential or commercial project.

Author:

Ms. Rebecca Lee

E-mail:

sale01@wddoorwins.com

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+86 13502225784