The installation joints of doors and windows in light steel villas are high-risk areas for thermal bridging. Improper handling can lead to rapid heat loss through metal components, causing condensation, mold, and even dripping on interior walls, especially in winter. The core issue lies in the difference in thermal conductivity between the metal door and window frames, the light steel frame, and the external wall insulation layer. A balance in thermal performance must be achieved through material insulation, structural optimization, and innovative construction techniques.
The application of thermally broken aluminum windows is a fundamental solution. Traditional aluminum alloy windows are prone to thermal bridging due to the high thermal conductivity of metal. Thermally broken aluminum windows, however, use physical insulation technology to divide the window frame into inner and outer parts, embedding a low thermal conductivity PA66 nylon thermal break strip in between. This structure interrupts the heat conduction path, reducing the overall thermal conductivity of the window frame by more than 60%. For example, using thermally broken aluminum windows in light steel villas can raise the indoor window frame temperature by 5-8°C in winter, effectively preventing condensation. During installation, it is crucial to ensure a tight fit between the thermal break strip and the aluminum profile to prevent gaps that could lead to thermal break failure.
The insulation filling process at installation nodes is crucial. The junction between window/door frames and the wall is a weak point in thermal bridging, requiring multiple layers of insulation material to block heat flow. Specific procedures include: first, filling the gap between the window frame and the light steel keel with expanded polyurethane foam, which has low thermal conductivity and expands to fill small gaps; then covering with insulating mortar or extruded polystyrene board to form a continuous insulation layer; finally, sealing the surface with waterproof sealant to prevent rainwater penetration and damage to the insulation structure. Some projects also add drainage channels under the window sill to prevent water accumulation and insulation material from becoming damp and failing.
The complete coverage of the external insulation system is a critical line of defense. Light steel villas typically use extruded polystyrene board or polyurethane board as the external insulation layer. During window and door installation, it is essential to ensure the insulation layer is continuous and uninterrupted. For example, adding an insulation frame around the window opening, extending the insulation board to the edge of the window frame, and securing it with anchors; using 45-degree beveled joints at corners to avoid vertical gaps forming heat flow channels. For protruding window sills or decorative moldings, an additional insulation layer should be added beneath them to prevent heat conduction through structural components.
Optimizing the joist arrangement can mitigate the impact of thermal bridging. In light steel villas, if the wall joists directly penetrate the insulation layer, linear thermal bridges will form. This can be addressed by staggering double rows of joists or separating joists at corners, breaking up continuous thermal bridges into segmented structures. For example, using denser joists around door and window openings enhances structural stability, while alternating main and secondary joists extends the heat conduction path. Some projects also apply reflective heat-insulating coatings to the joist surface to further reduce radiative heat transfer.
Insulation treatment for embedded pipes is often overlooked. Door and window installation joints often involve pipes penetrating the wall; if these pipes directly penetrate the insulation layer, localized thermal bridges will form. Rubber and plastic insulation sleeves should be wrapped around the pipes, and the penetration points should be sealed with expanding foam. For metal pipelines that must pass through the insulation layer, they can be replaced with low thermal conductivity materials such as PVC, or insulation modules can be added around the pipelines to ensure continuous thermal performance.
Refined control of construction processes is crucial. Strict control over the connection between each process is necessary during installation. For example, window and door frames should be positioned before insulation layer construction to avoid damaging the insulation structure during later grooving; expanding foam filling should be done in multiple layers to ensure a dense, void-free finish; sealant should be applied after the wall surface is dry to prevent adhesion failure due to excessive humidity. After construction, thermal testing should be conducted using an infrared thermal imager to scan the area around windows and doors to confirm the absence of abnormal heat flow concentration.
Thermal bridge control at window and door joints in light steel villas requires a complete closed loop, encompassing material selection, structural design, construction processes, and quality inspection. Through comprehensive measures such as thermally broken aluminum windows and doors, multi-layer insulation filling, external insulation system wrapping, optimized keel layout, and pipeline insulation treatment, the thermal bridge effect can be significantly reduced, improving the overall energy-saving performance of the building. This is not only related to living comfort but is also a key technological aspect of achieving low-carbon and environmentally friendly goals for light steel villas.
