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When purchasing windows, we often face quite a few problems, i.e., how to pick out the best, long-lasting, sustainable windows without overpaying for this necessity? The glass unit is the most expensive element of the window and it occupies the biggest part of it as well, therefore selecting a perfect glass unit is a very significant part of the entire window-choosing process. In the end it determines whether you will achieve the desired result or not.

When the weather turns cold, people frequently notice water condensation outside and inside the panes of their new windows. Why does this happen?
The main reason for water condensation is high humidity and poor indoor ventilation. At home the source of this problem is usually kitchen and bathroom premises that evaporate the biggest amount of water as well as the habitants themselves, who induce the evaporation when they breathe. The problem can be dealt with by ventilating the rooms properly, also it‘s necessary to let the air circulate by the window: when possible, don‘t shut the window tight with blinds or heavy curtains, don‘t place too many flower pots on the windowsill, don‘t install the heaters or radiators under the window. In the apartment buildings it is necessary to design air vents and self-ventilation systems. The reason why you probably didn‘t experience this problem with your old windows is because they were not completely hermetic and constantly kept “taking care” of the ventilation problem themselves, whether you wanted it or not. Of course, there is always a chance for water to condensate because of a defect of a faulty installation. Water tends to condensate externally on the glass units if the temperature of the glass surface is lower than the temperature of the atmosphere. High quality thermal glass units in your windows usually cause this by not letting the warmth out of your house.

What are the most frequent mistakes people make while choosing glass units for their home?
Mostly people pick the wrong spacers for their glass units. They usually lack the information and chose their spacers 6-8 mm wide – they are not wide enough neither to guarantee thermal insulation nor to noise-proof your house. Moreover, during the winter, if the window is somewhat bigger than usual, the glasses in the glass unit might burrow to each other and freeze to each other in the middle. We would advise choosing the spacers no less than 16 mm wide; and, if the windows are bigger, glass in the unit should be as thick as 6-8 mm. People rarely actually know that the thicker glass not only better preserves the heat, but also is safer and better suited for noise insulation.
Some clients while choosing decorated glass, also very persistently require putting the decorated side of glass inside the glass unit. This, of course, makes some sense, because compared to the patterned surface, smooth one is much easier to clean. However, if the decorated side of the glass is inside the unit it is virtually impossible for a window to be hermetic.

Which glass units should we choose to be able to keep the heat inside the house during the winter and not to fry out during the summer? For obvious reasons windows can’t be replaced every season, so they should meet our needs all year long.
According to various researches up to 50% of the heat evaporates through the walls; other 25% goes out through the windows and 13% – through the roof. More than this, windows not only leak out the heat during cold season, but they also raise the temperature in the rooms up during the summer. When the windows are not hermetic it‘s outrageously expensive to use conditioning systems: it costs up to three times more to lower the temperature in the rooms than to increase it. However, there are few rational solutions, depending on the benefits you are looking for in a glass unit. For example, an argon gas filled glass unit with two 4 mm thick glasses (one regular and one selective) has a thermal transmittance of 1.1 W/m2K. This window is “warmer” and cheaper than a regular triple pane glass unit, which usually has a thermal transmittance of 1.9 W/m2K (the bigger this number is, the “colder” the window). Triple pane unit with two selective glasses is ideal for people, who want to have a good thermal insulation during the winter and an effective solar heat protection during the summer. A glass unit with a composition of 4GNP-16Ar-4-12-Ar-4GNP has the best thermal insulation and heat protection qualities; the thermal transmittance of this unit is equal to 0.6 W/m2K, it has a 49% of solar energy permeability and 70% of light permeability. However, triple pane glass unit, especially if one or more glasses are thicker than 6 mm, are not recommended for using in large hinged windows or doors, because it may affect the hinges. It’s important to know that window frames should also be chosen in combination with the glass units.

How to choose the best spacers?
The spacers between the glasses in a unit may be either made from aluminum or from plastic. High-quality plastic spacers, compared to the traditional aluminum spacers, reduce the thermal bridge on the edge of the glass and help to avoid water condensation or mold. With no condensation to worry about, the window frames can be exploited longer – this is even more important for wooden frames. For example, using one of the most popular – TGI spacer – you will save 4.1% of the heat. There are multiple color variations of these spacers, so you will easily match it to you window frame.

The windows are becoming bigger and bigger; how can we protect ourselves from solar heat, and the furniture or floor from changing their color?
The windows are installed for longer than one season, so it is very important to know their solar and light transmittance ratios. If the windows are facing south, you should choose solar control windows; they will keep you warm through the winter and will protect from direct solar heat. Moreover, you will have the thermal characteristics of the house will be better. At the same time, these glass units are very well suited for light transmission: even when in a misty or foggy weather there is always enough light inside and the landscape hues outside the window are still seen natural. There is significantly less light coming in through the toned or reflection windows (almost two times less than using solar control windows): during the whole day these windows collect the heat and in the evening start radiating the heat into the room. Even more than this, toned windows must be tempered in order to protect it from breaking – this obviously increases their price. You should also consider whether it is necessary to install solar control glass units if the windows are facing north; perhaps it‘s enough to install them in the southern side of the building only as you will see no visible difference. Guardian’s Super Neutral 70 glass has exceptional light transmission qualities. The multifunctional coating minimizes the need for artificial light (visible light transmission is 70%) and offers excellent solar protection (solar factor is 41%) combined with outstanding thermal insulation.

What is a building energy pass?
European Union is using every opportunity to protect the environment we live in by controlling the CO2 emission from houses and other buildings. For this reason, the new 2002/91/EB directive has been initiated; this directive ensures that the owners of every building that is being built, renovated, put on the market for selling or renting would have an adequate energy efficiency certificate, compiled (in stages) of all the technical data and evaluation of the engineering systems. In Lithuania the directive is in force since 4th January, 2006. If the building doesn’t have the energy pass, it will not be authorized for exploiting. This is to ensure that all the buildings will not only save the money for people living in those buildings, but will be safe and meet the strict environmental requirements. For example in Denmark every building must have this document and it is written out again every time the building is renovated or sold.