Poles are becoming increasingly environmentally aware. According to research by Millward Brown SMG/KRC, in 2012, 64% of the country's residents insulated their walls, replaced their windows, or replaced household appliances with more energy-efficient models. There is also increasing discussion of passive and energy-efficient homes. The former are also known as “buildings with nearly zero energy consumption,” because heating them requires only 15 kWh/(m²•year). Energy-efficient homes, although they require somewhat more heat—from 30 to 60 kWh/(m²•year)—make it possible to significantly reduce heating costs compared with traditional buildings (which consume 90 to 120 kWh/m² annually).
The growing use of environmentally friendly solutions in construction is related, on the one hand, to rising fuel prices and, on the other, to the introduction of regulations promoting environmental protection. WFOŚiGW provides financial support for investments that meet the requirements, while the European Union expects all homes built after December 31, 2020, to comply with energy-efficiency restrictions. Meeting these requirements is inextricably linked to choosing materials that provide the best thermal insulation.
Is it all because of the window?
Thermal imaging analysis of buildings indicates that windows are a critical point in thermal insulation. Their lack of airtightness can account for as much as 15–25% of total heat loss. That is a lot, especially considering their small area compared with walls and the roof. Therefore, choosing window joinery with the best parameters is extremely important. “We can speak of energy-efficient windows when the Uw coefficient for a reference window is below 1.3 W/(m2K). The requirements are higher for passive construction, and Uw should be 0.8 W/m2K or lower,” says Artur Głuszcz from MS więcej niż OKNA.
The Uw coefficient specifies the amount of energy (or, more precisely, power) passing through a 1 m² window when there is a temperature difference of 1 K between the inside and outside of the building. Uw is the resultant heat-transfer coefficient for the entire window, but its value is affected by the parameters of the individual components: the glazing unit (Ug), profiles (Uf), and the type of spacer bar between the panes (Ψ). In practice, the insulation parameters of window joinery depend on the solutions and components used by the manufacturer, including the type of reinforcement, the number and width of chambers in the profile, the number of glass panes, and the type of spacer bar in the glazing unit. “The latest achievement in the insulation of PVC windows is SteelPUR® thermal reinforcement, made of two pieces of steel filled with polyurethane foam and fitted with a polyester-glass composite brace,” says Artur Głuszcz from MS więcej niż OKNA. “It eliminates the formation of thermal bridges and significantly lowers the Uw coefficient. This solution is used in MS evolution windows, which were recognized as ‘probably the warmest windows in Poland’ by Infookno 2013,” he adds.
The secrets of thermal transmittance
For convenience, most manufacturers provide thermal parameters for a reference window: a single-sash window measuring 1230x1480. Theoretically, therefore, to find out which of two window models is more energy-efficient, it is enough to check their Uw coefficients. However, caution is needed when comparing parameters. Manufacturers know that the insulating properties of windows are very important to their customers and that a low Uw coefficient often determines a purchase. As a result, there are cases in which information is provided unreliably or methods are used to artificially lower the coefficient. There are many examples of such negative practices.
Some sellers falsify data by providing the coefficient for a window with a roller shutter. Others provide the Uw coefficient not for a reference window, but for an oversized window measuring 1500mm x 1500mm. In this case, the resulting indicator is more favorable because the glass area is larger, and its thermal parameters are better than those of the profile area. Therefore, the safest approach is to independently check the Uw for a specific window model in exactly the dimensions intended for installation.
The actual thermal transmittance coefficient can easily be estimated using energy calculators available online. For example, the website www.uvalue.ms.pl can be used to calculate thermal parameters for single- and double-sash windows, a balcony window with a mullion, or a frame without a sash. Simply enter the width and height of the window joinery, and the system will generate the Uw and Ug values. These indicators are crucial to the window's insulating properties and, consequently, to whether the building will meet the requirements for passive homes. When choosing windows, it is therefore worth familiarizing yourself thoroughly with the offer of the most energy-efficient window joinery and carefully checking the parameters of specific models.
The energy-efficient windows described are available from:
Automatyka
ul. Kościuszki 19
59-700 Bolesławiec
Tel. 75 734 52 24, Fax. 75 734 52 26
Tel. Kom. +48 695 897 035
e-mail: biuro@automatyka-bramy.pl
www.automatyka-bramy.pl
www.facebook.com/pages/Automatyka-Boleslawiec/
