Energy efficient windows in the attic – which ones?

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Rooms in the attics are specific interiors which require not only the use of adequate thermal insulation but also properly selected roof windows to maintain proper thermal parameters. What should be the characteristics of energy efficient attic windows?

Why is choosing the right attic windows so important?

Attic windows are most often installed to illuminate the space with natural daylight. However, few people realize that it is through them that up to 40% of heat can escape from the house. Therefore, more and more emphasis is placed on the fact that the windows used in the attics have appropriate thermal parameters and are installed in the correct manner. The value that informs how much heat passes through the window is called the Uw coefficient. The lower it is, the less heat is lost through the window. The selection of appropriate windows in residential buildings is regulated by the Regulation of the Minister of Infrastructure dated 6.11.2008 (Journal of Laws of 2008 No 201, item 1238). According to it

  • facade and roof windows must not have a Uw coefficient higher than 1.3 W/(m2K),
  • windows in energy-efficient construction may not exceed Uw value of 1.1 W/(m2K)

Modern triple-glazed window construction

Classic attic windows consist of a single glazing package consisting of two panes separated by one chamber filled with argon or krypton

Nowadays more and more often in this type of constructions modern windows with double glazing are used. They consist of three panes separated by two chambers filled with noble gas. This type of windows have, above all, excellent thermal insulation parameters and reduce heat loss from rooms in which they are used

Triple glazed windows are offered by VELUX in the Standard Plus line. They are characterized by the heat transfer coefficient at the level of 1.1 W/(m2K). Additionally, they are distinguished by good parameters when it comes to the amount of sunlight delivered. As a result, the lofts on which they are installed will become energy-efficient and well-lit interiors

Warm roof window installation

Choosing roof windows with the right parameters does not guarantee full energy efficiency. Also important is the installation method. The best parameters can be ensured by the so-called warm installation of roof windows, which consists of three elements that eliminate the formation of thermal bridges that are most often responsible for heat loss in attics

What does warm installation consist of?

Warm installation of roof windows consists of three components. The first is a special insulation frame, usually made of polyethylene, which ensures a perfect fit of the window construction to the roofingmaterial.

The second is window insulation made of pleated fleece, which guarantees exceptional tightness

The last element is a drainage gutter mounted around the window, which drains away precipitation and moisture – preventing the covering under the window from getting wet and mold from growing in those areas

Thermomodernization relief for replacement of roof windows

If you are planning to renovate or adapt your attic for residential purposes, you should know that you may be eligible for a grant under the Thermal Upgrading Credit. All you have to do is to buy roof windows with energy-saving parameters, i.e. with a Uw index of 1.1 W/(m2K), and then, on the basis of invoices for their purchase and installation at the end of the year, deduct the costs incurred in connection with the work done from your income tax. What is important is that the amount of deduction in this case can not exceed 53 000 PLN

When choosing roof windows for the attic you should first of all pay attention to their heat transfer coefficient, which should be a minimum of 1.3 W/(m2K), and preferably 1.1 W/(m2K). In addition, it is also worth investing in a warm installation system when fixing them, which will increase energy savings

Peter Bowers

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