Nowadays, people pursue energy saving in many ways, such as home energy saving. Energy saving can also be achieved through the design and materials of doors and windows. So, how exactly is energy saved? What materials should windows and doors use to be energy efficient? Doors and windows made in China can provide the answers.
The advantage of energy-efficient aluminum alloy lies in its energy-saving properties. For example, the aluminum alloy frame can effectively support thick or hard glass because aluminum alloy has the strength to hold the weight of thick glass. Thicker glass can prevent outdoor high temperatures from penetrating inside, thus maintaining indoor temperature well and providing a comfortable feeling.
- Core Energy-Saving Principle of Energy-Efficient Aluminum Alloy Windows
The essence of energy saving in aluminum alloy windows is achieved through material innovation, structural optimization, and technological upgrades to build an efficient thermal insulation system that precisely controls heat transfer between indoors and outdoors. The core logic revolves around reducing the heat transfer coefficient—by blocking the heat conduction path of aluminum profiles, enhancing the thermal insulation performance of glass, and reinforcing sealing structures to reduce air infiltration. Together, these form a comprehensive energy-saving protective system.
According to the General Code for Building Energy Conservation and Renewable Energy Utilization, window K-values (thermal transmittance) are strictly regulated in different climate zones. Energy-efficient aluminum alloy windows can control K-values between 1.0 to 2.0 W/(㎡·K), far superior to ordinary aluminum windows.
Energy-efficient aluminum alloy has strong compressive strength and sealing properties, which are key reasons why many consumers firmly choose Chinese-made doors and windows.
- Key Energy-Saving Technologies in Energy-Efficient Aluminum Alloy Windows
(a) Thermal Insulation Design of Profile Structure
Multi-chamber Structure Optimized for Mechanics and Thermodynamics
Energy-efficient aluminum alloy profiles use multi-chamber hollow structures. By increasing the number of internal air chambers, they leverage air’s low thermal conductivity to create a natural heat barrier. For example, mainstream 65-series window frame profiles have cavity designs that reduce the profile’s heat transfer coefficient by 30%-40%. Meanwhile, the cavity geometry is optimized via fluid dynamics simulation to reduce the “thermal bridging” effect where hot or cold air transfers through the profile walls. The multi-chamber structure effectively reduces outdoor high temperatures penetrating indoors, acting as a thermal barrier.
Material Innovation and Structural Improvement of Thermal Break Strips
Material Upgrade: PA66GF25 nylon thermal break strips replace traditional PVC strips, which are cheaper but less weather-resistant and prone to softening at high temperatures, causing thermal bridge failure. PA66GF25 has tensile strength ≥ 80 MPa, heat distortion temperature ≥ 220℃, and stable performance between -40℃ and 80℃, effectively blocking heat conduction paths in aluminum profiles.
Structural Innovation:
Double thermal break structure: Two thermal break strips are set at the window frame and sash joints, creating a “double thermal barrier layer,” reducing the overall heat transfer coefficient by 15%-20%.
Thermal break cross-section optimization: Complex cross-sections like “C” or “T” shapes increase the heat flow path length. For example, a certain brand increased strip length from 14mm to 24mm, improving thermal resistance by 60%.
Energy-Saving Auxiliary Role of Surface Treatment
Powder coating: Electrostatic powder coating forms a heat-reflective layer that reflects solar radiation. Light-colored coatings (such as silver-white) can achieve solar reflectance above 0.7, reducing heat absorption by the profile and indoor heat gain in summer.
Fluorocarbon coating: Fluorocarbon (PVDF) coatings provide excellent weather resistance and low surface energy, reducing dust accumulation and maintaining stable heat-reflective performance.
(b) Thermal Insulation Technology of Glass Systems
Glass is the main carrier of heat loss in windows. Energy-efficient aluminum alloy windows use the following technologies to create high-performance glass systems:
Optimization of Insulated Glass Structure
Multi-chamber insulated layers: “Double-seal” process uses inner butyl sealant to block moisture and outer silicone sealant to reinforce structural strength. Insulated layer thickness is upgraded from traditional 12mm to 16mm or 20mm; thermal resistance increases non-linearly with thickness (R=0.28 ㎡·K/W at 12mm; R=0.35 ㎡·K/W at 20mm).
Inert gas filling: Filling argon gas (thermal conductivity 0.017 W/(m·K)) or krypton gas (0.009 W/(m·K)) in the cavity replaces air to reduce convective heat transfer. Argon can reduce the K-value by 0.5-0.8 W/(㎡·K). Krypton performs better but costs more.
Warm-edge spacers: Replace traditional aluminum spacers with stainless steel, TPE (thermoplastic elastomer), or composite strips having thermal conductivity ≤ 0.1 W/(m·K) (aluminum spacers ~237 W/(m·K)) to reduce “cold bridge” effects at glass edges. For example, a TPE warm edge spacer can raise glass edge temperature by 3-5°C and reduce condensation risk.
Composite Use of Functional Glass
Low-E glass (low-emissivity glass): Multiple metal or composite coatings (silver, tin, nickel-chromium alloy) are applied on the glass surface (only 0.1-0.5 μm thick) to reduce far-infrared emissivity from 0.84 (ordinary glass) to below 0.1. Different coating types include:
High-transparency type (visible light transmittance > 70%), suitable for areas needing strong natural light.
Shading type (solar heat gain coefficient SC ≤ 0.5), suitable for hot summers and mild winters.
Energy-saving laminated glass: Besides safety, laminated glass (e.g., with PVB interlayer) absorbs infrared radiation, blocking some heat transfer. Combined with Low-E glass into “Low-E laminated insulated glass,” K-values can drop below 1.0 W/(㎡·K), suitable for very cold regions.
Triple-glass double-cavity structure: Uses three panes + two insulated cavities (e.g., 5mm + 12A + 5mm + 12A + 5mm) with inert gas filling and Low-E coatings. The whole window’s K-value can decrease to 1.3 W/(㎡·K), but weight increases by about 30%, requiring reinforced hardware.