- Martin Labedz
What you need to know about glazing
Among many factors we need to consider when searching for the right window is the glazing within it. Since glazing takes up the significant majority of the window’s surface area, its thermal properties will largely determine the U-value of the entire window. It’s worthwhile spending the time to select the most suitable glazing unit – durable, well-sealed and well-designed. This choice can affect the resident’s comfort, security and wallet – it is therefore an important aspect when selecting windows.
Single glazing is a thing of the past, the standard nowadays being double- and triple-glazed sealed units with a spacer bar and an insulating gas filling. Sealed glazing units not only significantly improve the heat retention of the window, but also positively affect factors such as security, sound insulation and solar control.
The most effective solution is a glazing package filled with one of the noble gases. Argon or krypton injected between the glass significantly improves the window's thermal properties. In addition, a special coating made of the noble metal oxides applied to the glass, commonly known as low-e coating, further improves its thermal performance. This is because the additional layer transmits light and solar energy to the interior of the house, but blocks their escape. It is worth mentioning that these coatings are barely visible to the human eye, but can reduce heat loss through the package by over 50% compared to an uncoated glazing unit.
The importance of spacer bars
Apart from the elements mentioned, the glazing unit is also equipped with a spacer bar. It is worth the attention, because it is this part of the package that ensures the glass panes are located at an adequate distance from each other. It’s also important to note whether the frame between the panes is bent or cut in the corners. Naturally, the former is a better solution – a uniform frame minimizes leaks from inside the package.
Lastly, consider what material the spacer bars are made of. Although aluminum or steel remain the most popular raw materials, they are rightly called "cold frames". A much better solution are ”warm” Warmatec frames made of steel-plastic composite. You will find them in all Oknoplast windows on the Irish market. Their characteristic feature is five times lower thermal conductivity, thanks to which they can improve the heat transfer coefficient – Uw – for the whole window by up to 8%!
A good sealed glazing unit consists of several important elements. These are:
· Glass panes (minimum two)
· Glass low-emission coating
· Spacer bar (otherwise known as distance frame)
· Noble gas filling – most commonly Argon
· Primary sealant – butyl
· Secondary sealant – e.g. polysulfide or polyurethane
Types and functions of glass
At the heart of every glazing package is the glass. They have different properties depending on their construction and materials. There are five types: thermally insulating, safety, solar control, ornamental and acoustic.
A. Thermally insulating glass
Designed to reduce heat loss. The package may consist of Float glass (transparent, no optical distortion) and/or Thermofloat (low-emission, reflect thermal radiation). It is possible to use 2 – 4 panes, which translates into Ug values in the range of 1.3 – 0.3 W/m²K.
B. Safety glass
This solution takes into account primarily the safety of household members and increased resistance to breaking attempts. P2 panes consist of two panes of glass and two layers of PVB, while P4 panes are also two panes of glass, but four layers of foil.
The increased safety is also influenced by toughened glass, whose strength is up to 5 times higher when flexed compared to ordinary glass.
C. Solar control glass
This type of glazing prevents the overheating of rooms. The solar control package may contain absorbent, reflective or selective glazing. The first absorb solar energy, the second reflect light radiation, while the third protect against overheating while possessing thermal insulation properties.
D. Ornamental glass
Offer mainly a decorative function. The Oknoplast offer includes as many as 24 patterns of ornamental glass, so everyone will find something for themselves.
E. Acoustic glass
Also known as soundproof, they combine the functions of thermal and sound insulation.
Acoustic insulation is improved by increasing the thickness of the glazing unit and the use of glass panes with acoustic foils in the composition. The standard 4/16/4 single-chamber glass produces a sound insulation of 31dB.
Windows produced by Oknoplast can have acoustic insulation up to 47dB. It should be highlighted that this is not the sound insulation value of the whole window, but rather the glass itself. The window's value is usually lower.
Find out more about glazing and windows at www.oknoplast.ie