Energy-efficient windows - how to choose them?

Heat escapes from the house through the glass surfaces faster than through the walls. To maintain the room’s optimal temperature and improve the building’s energy balance, it is worth investing in energy-efficient windows. What to look for when buying them, and which window series is worth taking a closer look at?

The heat transfer coefficient of windows.

The window's heat transfer coefficient, Uw, informs us about the level of window thermal insulation. The Uw value shows how much heat will penetrate a square meter of a window in one hour, with a temperature difference (between the environment on one side of the window and the interior on the other) of one degree. This means that the lower the Uw coefficient, the better the window's thermal insulation is. When looking for energy-efficient windows, it is essential to ensure that their Uw value is as low as possible.

What elements of the window affect its thermal insulation?

The selected glazing unit is of particular importance in terms of thermal insulation of the window. The heat transfer coefficient of the glazing unit is marked with the symbol Ug. The number and type of glazing are essential. Nowadays, double-glazed windows are rare, and the most popular are triple-glazed windows; some even opt for glazing units four-glass. It is necessary to equip the window with a warm edge and the right type of gas that fills the pane’s spaces (high-quality glazing should be filled with special gas.

However, the Uw value is also influenced by the thickness and quality of the window profile, gaskets (energy-saving windows are often equipped with additional gaskets), and hardware.

Are windows with the permissible Uw energy-saving?

The term "energy-saving windows" is often misused. Manufacturers ensure that windows have an excellent heat transfer coefficient, as it meets European standards. Windows with the highest allowable Uw will be airtight and usually provide better thermal insulation than older models, but certainly cannot be considered energy-saving or passive windows.

Which windows to look for?

Windows with a Uw below 1.1 are already windows with sufficient parameters, often chosen for single-family homes. However, an excellent heat transfer coefficient is when it is lower than 0.9 W / (m2 * K). If the investor is interested in the maximum reduction of energy losses, it is worth choosing windows with the Uw coefficient not higher than 0.8 W / (m2 * K).

Window series providing excellent thermal insulation.

For customers looking for windows that guarantee good thermal insulation, we recommend the following series of DAKO windows:

  • DPQ-82 thermoSecure – a series of vinyl windows that ensures maximum energy efficiency and additionally increases the level of safety. The series offers an excellent heat transfer coefficient - at the level of Uw = 0.75. It is possible, among others, thanks to the three-glass package with special ECLAZ glass filled with argon, the warmest inter-pane frame, seven-chamber A-class profile with a thickness of 82 mm, three gaskets, and thermal insulation inserts in the frame and sash. We recommend this series to customers who care about high-quality and energy-efficient windows - it is the warmest solution available at DAKO.
  • DPQ-82 – a series of PVC windows, also ensuring energy efficiency - offer Uw at an excellent level of 0.77.
  • DPQ-76 – is a series of PVC windows that provides high thermal insulation (Uw = 0.87) at an attractive price. A good compromise between the price and excellent thermal insulation.
  • DDF-78 i DDR-78 – among wooden windows, in terms of the thermal insulation provided, two series stand out: DDF-78 and DDR-78, providing Uw at an adequate level of 0.82. A high-quality profile with a thickness of 78 mm, three retractable seals, and a triple glazing unit filled with noble gas make these windows an excellent choice for customers looking for elegant, energy-saving windows.

Thermal insulation and installation of windows and exposure to the directions of the world and window covers.

To be sure that the selected windows will provide a high level of thermal insulation and help guarantee the building’s right energy balance, it is also necessary to ensure proper installation. Errors can be made while installing the window joinery, resulting in the windows quickly losing tightness. Two of the most common problems are installing the window on an unclean surface and using the wrong insulating foam. To avoid issues with window tightness, it is best to leave the installation to professionals.

The display of windows is also essential. Remember that there is little light coming into the windows on the north side. As a result, the rooms are dark and not heated by the sun's rays. This leads to a negative impact on the energy balance of the building in the colder months.

Additionally, to improve the window’s thermal insulation, it is essential to have appropriate window covers, and external blinds are always a right choice. In winter, they can slow down the loss of heat from heated rooms and, in summer, make the interior less warm, leaving the conditions at home are more comfortable, and the costs of heating and air conditioning are reduced.

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