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thermal bridging around windows

Thermal Bridging in window applications

What causes thermal bridging around windows? What are the most effective interventions to prevent and resolve it?

Eliminating thermal bridging around windows poses a significant challenge in energy-efficient design. Thermal bridges pose a threat to living comfort and the energy balance of homes, making it mandatory to find solutions during the design phase.

In this article, we delve into the issue of thermal bridging around windows and practical solutions to eliminate it, ensuring a more comfortable and sustainable living environment.

To ensure accurate analysis and precise verification of solutions, you can use a thermal bridge analysis tool, as demonstrated in the accompanying video.

Thermal bridge fixed in the center of a wall insulated from the outside with a flap

Thermal bridge fixed in the center of a wall insulated from the outside with a flap

What Is a Window Thermal Bridge?

A window thermal bridge is a significant issue in building energy efficiency. This architectural flaw occurs when there is an imbalance between construction materials or when necessary precautions are not taken during window installation, resulting in heat or cool air leakage into the home due to a “cold” or “hot” spot that encourages airflow from outside to inside.

The lack of thermal insulation, such as in a concrete structure combined with brickwork or a steel structure with other materials, is the root cause of window thermal bridging. Resolving this issue involves restoring balance between construction elements. Mold and condensation, particularly common problems in homes, are often caused by the presence of thermal bridges around windows.

Therefore, careful attention to the correct installation of windows is essential, paying particular attention to all window components to create a perfect connection between the window element and the masonry, resulting in a building envelope free of thermal bridges.

Unfortunately, not all industry operators adopt necessary practices to ensure proper window installation, often simply fitting windows without sufficient attention to detail. Therefore, it is advisable not only to consider window prices but also to inquire about detailed installation procedures.

Thermal bridges around windows can be avoided or mitigated through carefully studied installation methods to achieve the perfect window opening renovation. This approach not only solves or prevents mold and condensation problems that negatively affect living comfort but can also contribute to improving building energy efficiency, leading to higher energy certification classes.

According to UNI 10818 and UNI 11673-1 regulations, the designer is responsible for selecting the type of window, identifying performance levels, and drafting the executive project for joints between the window and surrounding technical elements, paying particular attention to window fixing to the support, reducing thermal/acoustic bridges, and ventilating spaces. It is also important to evaluate morphological, dimensional, and physical compatibility between the window and surrounding elements, as well as conducting thermal analyses and condensation checks to ensure correct window installation and reduce thermal bridges.

Effects of a window thermal bridge

Effects of a window thermal bridge

How to Eliminate a Window Thermal Bridge

As we have seen, the causes of thermal bridging can be manifold but can be (not always) predicted, studied, and therefore corrected and eliminated.

Eliminating or reducing thermal bridges around windows requires targeted intervention. There are several feasible solutions to address this issue, depending on the specific conditions of the building and windows.

Resolving Thermal Bridges Caused by a Pass-Through Sill or Threshold

One of the most common cases is the presence of a pass-through sill or threshold, where the marble slab or other material extends from the exterior to the interior, transmitting heat or cold from outside to inside the home. To solve this problem, it is necessary to interrupt the thermal bridge by cutting the slab and inserting insulating material between the two parts of the sill. This process, similar to that used for thermally broken windows with double glazing, ensures the separation of the two surfaces to prevent heat conduction.

Solutions for Thermal Bridges Caused by the Cassette

Another critical point is the cassettes, representing one of the most common thermal bridges in homes. When replacing windows with high-energy performance models, such as Class A, it is essential to also address cassettes to avoid thermal bridge formation. Replacing the cassette with a thermally insulated model or inserting adequate insulation is an effective solution to address this issue and prevent mold and condensation formation inside the structure.

Dealing with Thermal Bridges Caused by Metal Counterframes

The perimeter metal counterframe represents another critical point in terms of thermal bridges since iron is a good conductor of heat. In the presence of high-energy performance windows, the risk of thermal bridge formation is high. To mitigate this issue, it is advisable to replace the metal counterframe with a thermal structure or make a cut around the perimeter of the counterframe using specific tools. While this solution may improve the situation, it does not completely solve the problem but can help reduce its impact.

Correcting Balcony Thermal Bridges

Similar to windows, balconies can also be subject to thermal bridge formation due to the materials used and the lack of adequate insulation. To address this issue, it is possible to install an insulating system on the entire balcony facade or insert insulating elements. Thanks to technological innovations, such interventions can also be carried out on very old buildings, thereby improving energy efficiency and living comfort.

Thermal Bridge Calculation

Below, I want to show you a video on the use of software for thermal bridge calculation, which facilitates identifying thermal bridges.