Why opt for energy-efficient windows?

18 of August '22

Growing ecological awareness, a sense of responsibility for the common future, and finally real profits in the form of lower heating bills are causing more and more people to choose energy-efficient windows.

What are energy-efficient windows?

Energy-efficient windowsare woodwork with excellent thermal insulation properties. It is characterized by low thermal transmittance, thanks to which we feel thermal comfort. Secondly, it lets the optimal amount of natural light into the building. Keeping in mind the savings and the interest of the environment, let's choose windows made of durable materials that do not need to be replaced for many years, such as aluminum. It works well as a window component because it has good anti-corrosion properties. It is resistant to rain, snow and frost. In addition, it takes only a few percent of the energy used originally, to recycle aluminum.

How airtight and warm our window will be is also greatly influenced by the glazing itself. And although a triple-glazing package with two chambers is already standard, if you care about an energy-efficient or passive home, it should be remembered that each additional sheet of glass generally means less light penetration into the interior. Access to the sun's rays is not only about bright rooms and beautifully illuminated arrangements, but the actual impact on our mood, concentration, energy and broadly understood quality of life. This is because it is assumed that natural light can increase our concentration by up to 15%, reduces the risk of experiencing low vital energy and supports the production of vitamin D. It is worth choosing models from well-known companies. After all, this is an investment for years. In addition, they often release products that not only meet energy-saving requirements, but also exceed these ever-tightening requirements.

Okna energooszczędne to ekologiczny i opłacalny wybór

Energy-efficient windows are an eco-friendly and cost-effective choice

© Veka

Uw, Lt, g, Rw, C, Ctr, RC - what do these abbreviations mean?

The Uw parameter tells us how much heat escapes per hour through a square meter of a given window, with a temperature difference of one degree Celsius inside and outside the room. The lower the coefficient, the better - because it means that the glazing will be tight, and more heat will be left in the room. In practice, this means that a Uw of 0.7 W/m2K is an unquestionably better choice than one reaching 1.0 W/m2K. For buildings heated with coal or wood, replacing windows with those with low Uw will reduce greenhouse gas emissions and air pollution. And with electric or gas heating, it will significantly reduce bills. Keep in mind, however, that the final result is also influenced by the g-value of the glass and the Uf-value of the window frame.

How much light a high-quality glazing lets into our interiors is informed by the coefficient Lt. After all, one of the main tasks of windows is to illuminate rooms, and how much sunlight will be let through the glass is of considerable importance in this case. It can be assumed that a standard three-pane package lets up to 70% of light through. The higher, the better, because it means that the window does not stop light and does not distort it. The parameter itself, taken out of context, may not be so impressive, but if we juxtapose it with the latitude where we live, the benefits of a high Lt percentage seem to be unmatchable. Relatively short and not always sunny summers, rainy and cold autumns, winters that are difficult to predict - they are easier to survive in a bright and, above all, warm interior. Good illumination will translate into a better mood of household members and improve the visual perception of any interior.

Okna energooszczędne wyróżniają się doskonałymi właściwościami termoizolacyjnymi

Energy-efficient windows are distinguished by their excellent thermal insulation properties


Speaking of the glazing itself, it is also worth devoting a few words to the coefficient of total energy transmittance - g. It is expressed as a percentage. The higher its value, the greater the passive energy gains. Thus, under the influence of the sun, the rooms will heat up more. This, of course, translates into thermal comfort and savings on heating. Burglary protection is expressed by the RC scale, where RC1 means that the woodwork offers the least resistance, while RC6 means that it offers the greatest resistance. It is therefore worth looking at the fittings used by the manufacturer, which are designed to fully hold the sash in the frame catches, as well as the glazing package, which should be tempered and reinforced with PVB film. Such a combination will effectively make it difficult for a burglar to break the glass and get inside.

Rw is the soundproofing coefficient. This is, in other words, the efficiency with which a partition reduces the level of sound, the source of which is outside. Like noise, it is measured in decibels dB. The higher its value, the less sound will enter the room. For example, if the source of noise outside the building is 55 dB, and the window has an Rw of 30 dB, we will hear a sound of about 25 dB in the room. Why about and not exactly 25 dB? Rw is always accompanied by two additional parameters specific to specific types and sources of noise. The C symbol indicates by how much the sound attenuation capacity of expressways, trains or air traffic decreases, while the Ctr marker refers to noise in which low tones predominate. Soundproofing should not be underestimated - with a difference of 5 dB our perception of annoying tones decreases by as much as 30%.

Szczelność okien w dużym stopniu wpływa na zmniejszenie kosztów ogrzewania

The tightness of windows greatly affects the reduction of heating costs

© MS more than OKNA

How much can you save?

Leaky windows in the house are associated with large losses. Up to 30% of heat escapes through old or defectively installed glazing.

- If we assume that the U-factor is 1.0 W/ (m2-K), the windows in a single-family house have an area of 100 m2, and the temperature difference is 30 K (+20°C and -10°C outside), 3000 K will escape. This is because we multiply all the coefficients, i.e. 1.0 W/ (m2-K) × 100 m2 × 30 K = 3000 W, and then take into account the elapsed time. Each hour of heat loss is 3000 Wh, or 3 kWh, and this must be balanced by the heating system," emphasizes Pawel Wozniak, an expert of the OknoPlus brand.

Assuming that 1 kWh costs us 0.69 - 0.78 zlotys, we can save about 56 zlotys when heating around the clock. Over the course of a month, this gives us 1,740 zlotys. The previous heating season lasted from September to May, so 9 months. This means that by replacing the windows with energy-efficient ones, we are able to save 15,660 zlotys in heating bills over the year.

WT21 standards

As of January 1, 2021, every newly built single-family house must meet the energy efficiency standards of the WT21 regulations. This is a series of guidelines on, among other things, energy efficiencyand insulation that must be met when erecting a dream home. With this change, a pro-environmental approach to construction functions as a standard. This means, among other things, that the heat transfer coefficient for all commercially available façade windows must not exceed 0.9 W/m2K. For windows in passive houses, the value is 0.8 W/m²K. The amendment does not apply to buildings that have already been built.

Energy-efficient windows let the optimal amount of natural light into the building


Subsidies for the purchase of energy-efficient windows

However, owners of finished buildings should also not give up the thought of replacing their windows with more environmentally friendly ones. For these people, the government's Clean Air program is designed. Its goal is to improve air quality and reduce greenhouse gas emissions into the atmosphere by replacing heat sources and improving the energy efficiency of residential buildings. Accordingly , we can apply for funding for energy-efficient windows that meet the requirements of WT21. Beneficiaries can take advantage of two forms of support - a subsidy system and athermal rehabilitation allowance. In the first case, the scope includes not only replacing old, inefficient heat sources with modern systems, but also carrying out the necessary work to improve the thermal insulation of the building - including the modernization of window frames. The amount for the basic level of subsidy can be up to 30 thousand zlotys for a project with photovoltaic micro-installation. This is a sufficient subsidy for windows to get a modern and ecological solution with parameters much better than those stipulated by the law. Importantly, beneficiaries can apply for subsidies for energy-efficient windows only for existing buildings.

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Development: Katarzyna Szostak

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