Distance frame for double-glazed windows - types and purpose

The spacer frame is one of the components of the double-glazed window design. Like all other details, it is of great importance. The frame is part of the frame of the glass unit and separates the sheets of glass at a certain distance. The appearance of condensation on the surface of the glass also depends on the distance frame - whether the glass will fog up or not.

To prevent the glass from fogging up, the spacer frame is filled with a desiccant. Its purpose is to absorb moisture from the space between the glasses and prevent condensation. For this purpose, there are diffusion holes along the entire length of the front side of the frame.

The three most common materials for making spacer frames are:

• Aluminum;
• Cink Steel;
• Plastic.

Aluminum frames

Aluminum is the most common material for the production of spacers. Aluminum distances are a profile with double-row perforation.

There are two types of aluminum frames:

• Rigid - as the name suggests, they are not elastic. They are assembled using steel or plastic corners and are trimmed on machines.
• Flexible - can be bent either manually or using equipment.

The production of aluminum frames, although an old technology, is time-tested and very practical and the most popular to this day.

Spacer frames made of galvanized steel

A steel spacer frame has its advantages compared to an aluminum one.

One of the advantages is the absence of a “cold bridge”. It appears when spacers made of materials with increased thermal conductivity are used to fasten a double-glazed window. Of the three main materials (aluminium, steel, plastic), galvanized steel has the lowest thermal conductivity coefficient. The use of a steel spacer significantly reduces the chance of a temperature bridge occurring.

To ensure long-term reliability of plastic double-glazed windows, the decisive conditions are the selection and preparation of both the above-mentioned structural materials and high-quality sealing of the double-glazed window with a rubber seal.

Another advantage of a frame made of galvanized steel is that when the temperature changes, it moves relative to the glass 8.26 times less than its aluminum counterpart. This means that steel frames can reduce the number of mechanical damage to glass and extend its service life.

Advantages of steel spacer bar:

• Reduced moisture condensation;
• Absence of “cold bridges” (temperature bridge);
• The elasticity of steel allows the frame to be bent even at a right angle.

Why a spacer frame in a plastic window?

Glass and inert gas make it possible to warm the entire structure of the double-glazed window as a whole, and the warm spacer frame is responsible for the edge zone of the double-glazed window. In professional terms, the edge zone is the most vulnerable - a “cold bridge” is formed here. But in fact, everyone knows what it is: in cold or frosty weather, the window freezes along the edge - condensation or ice forms, and, what is most unpleasant, they arise from the inside, in the room.

Photo: condensation around the perimeter of the double-glazed window confirms that the aluminum spacer frame is the weakest link in the double-glazed window. This is not only not aesthetically pleasing, but also indicates that your window is simply losing heat. To prevent this from happening, a “warm” frame is inserted into double-glazed windows of the best quality.

Plastic spacers

Plastic began to be used for the production of spacer frames relatively recently, but it has already gained popularity due to its many useful qualities. The main advantage of plastic, as well as galvanized steel, is its low thermal conductivity coefficient. PVC frames effectively prevent the formation of condensation in the interior of the window.

Temperature fluctuations do not affect the plastic in any way, which allows it to maintain its original shape for a long time.

So, here are the functions of a spacer for double-glazed windows:

• Provides distance between glasses;
• Protects free space from moisture and condensation;
• Acts as a frame for a double-glazed window.

Warm spacer frame - features and purpose

A spacer frame is a part of the double-glazed window frame that separates the sheets of glass at a specific distance.

Warm edge frame

It depends on whether the windows will fog up. To avoid this, spacer frames (profiles) are filled with a special desiccant. It absorbs moisture from the space between the glass, creating an air or gas heat-insulating chamber. Therefore, along the entire length of the front side of the profile there are perforated (diffusion) holes. The size of such holes is smaller than the diameter of the molecular sieve granules poured into these recesses.

Design of double-glazed windows with spacer profile

Plastic spacer frame , as well as frames made of other materials:

1. Creates equal spaces between the glass panes along the entire length of the glass unit.
2. Protects empty space from condensation and moisture ingress.
3. Serves as the primary frame for double-glazed windows.

To create better tightness inside a double-glazed window, the method of bending (bending) the spacer frame is often used. Another way: cutting a spacer frame, for example, plastic, and then assembling straight parts and corners for a spacer frame. The joints between the profiles are filled with butyl sealant.

Spacer saw

The distance frame for double-glazed windows has the following dimensions: 5.5 mm, 7.5 mm, 8.5 mm, 9.5 mm, 11.5 mm, 13.5 mm, 14.5 mm, 15.5 mm, 17. 5, 19.5 mm, 21.5 mm, 23.5 mm. This is the possible thickness of the spacer frame. And the optimal width of the spacer frame is 10-16 mm.

If the profile width is less than 10 mm in winter, the glass in the double-glazed window may stick together due to a decrease in the pressure inside it. This phenomenon (sticking) can also appear for other reasons during the manufacture of a double-glazed window:

1. Atmosphere pressure.
2. Air temperature inside and outside the room.
3. Molecular sieve quality.
4. Pressure and temperature.

Do you find it difficult to choose a quality profile for a window? Read the article at:

Thermoplastic spacers

Or as they are called - TPS, were developed by the German company Lenhard. This technology eliminates the use of metal frames. Instead, thermoplastic frames made of polyisobutylene are used, which ensures low thermal conductivity of the frame. Thermoplastic sealant is also used along with the frames, providing maximum protection against moisture.

Advantages of TPS:

• Automated production, which significantly reduces the defect rate;
• Excellent tightness;
• The elastic design ensures resistance to mechanical stress, temperature and pressure changes;
• Support for glass units of various shapes;
• Good adhesion to glass.

Advantages and disadvantages of spacers

Rice. 13. spacers of different types

The most significant advantage of spacers is the ability to retain heat indoors. Energy-saving properties are especially noticeable in winter, when space heating is required. The window opening often becomes the place that “releases” some of the heat to the street.

Today there are many ways to make a window opening as insensitive to temperature changes as possible, at which there is no “return” of hot air to the outside or vice versa. But some of these methods are based on darkening the glass. Distance frames allow you to maintain transparency, but at the same time protect the room from unnecessary expenses on climate control equipment. First of all, this is the width of the profiles. A two-chamber product must use tubes of different widths, otherwise there will be no differences from a standard single-chamber window. The frames also create maximum tightness of the inter-window space, maintaining a “warm” air gap.

The most “wasteful” are aluminum profiles, since their thermal conductivity rates are quite high. In addition, some profiles are difficult to work with; they fit only on standard rectangular frames, although today the geometry includes round portholes and polygonal glazed attics.

Swingle Strip Technology

This technology involves sealing a double-glazed window using an elastic tape with a sealant, an aluminum bridge and a desiccant.

The purpose of Swingle Strip technology is to simplify the process of sealing windows. The tape combines the functions of a spacer, sealant and desiccant. The installation process of such a tape takes very little time, which significantly speeds up the production process.

Advantages of Swingle Strip technology:

• Fast and easy sealing process;
• High resistance to moisture and temperature fluctuations;
• Protection against condensation.

TGI technology

TGI spacer frames are made of polypropylene foam and stainless steel film. Foam propylene improves thermal insulation and strengthens the profile. The film prevents gas penetration.

The use of these materials allows you to obtain a warm edge. The technology involves the use of a desiccant - an adsorbent, which is poured into the cavity of the spacer frame (Previous technologies do not require the use of this material). Molecular sieves, silica gel, and mixtures of both products are used as desiccant.

Using the most commonly used types of molecular sieves, very low dew point temperatures (mostly −60°C) can be achieved. The use of silica gel does not give such low dew point temperatures, on average about −45°C.

Advantages of TGI technology:

• Good thermal insulation/low thermal conductivity;
• Insulated edge on the room side;
• Best protection against condensation;
• UV resistance.

PVC frames

PVC frames have the same design as their aluminum counterparts, differing only in the material of manufacture. Such frames have high thermal insulation, are resistant to UV radiation, protect against condensation and can withstand temperature changes well. It should be noted that for PVC frames you should use not a traditional polysulfide sealant, but a polyurethane one - it has better adhesion to PVC and copes better with moisture.

Advantages of PVC frames:

• Thermal insulation;
• Resistance to temperature changes;
• Improved sealant that better resists moisture.

Super Spacer technology

Distance frames using this technology are produced mainly in the USA. They are made of polymer foam, which means extremely low thermal conductivity - 950 times less than that of aluminum slats. Another advantage of Super Spacer is its design flexibility, which allows it to be adjusted to fit glass units of a wide variety of shapes.

List of all the benefits of Super Spacer technology:

• Increased glass temperature by an average of 80%;
• 70% improved resistance to moisture and condensation;
• Less load on the sealant, which improves the elasticity of the glass unit;
• Reduced heating costs;
• Protection from harmful solar radiation.

Manufacturing technologies

Material is not the only indicator that allows you to classify spacers. The second important parameter is the manufacturing technology, which is determined by the sealing compounds and other components necessary for the work. The main methods are as follows:

• Thermoplastic (TPS) technology is based on the use of plastic, PVC and other polymers. Metals are not used. A special production scheme ensures the strength of the frame; when bending, punctures and cracks do not form. The sealing composition guarantees not only a tight fit, but also the ability to absorb excess moisture. Temperature effects do not disrupt the geometry of the structure; it remains sealed and durable. The use of polymer materials also makes it possible to form frames of complex configurations; there are no restrictions on the number and angles of bends;
• SwingleStrip is a technique that involves ensuring tightness through a multi-layer structure. The main component is a sealant that absorbs excess moisture. A layer of sealant is distributed over the glass sheets like a dense tape, then an aluminum-based material is placed, and a desiccant is placed on top. Despite the multi-layer nature, the technique is quite simple to use and allows you to set up production with minimal costs;
• TGI technology, in which rigidity is provided by a hollow metal tube. To achieve resistance to cold, a special film is used and treated with a composition that reduces the coefficient of thermal conductivity and eliminates deformation due to temperature fluctuations. Inside the tube there is a drying compound in the form of granules. The combination of film and special composition makes the finished structure more resistant to mechanical stress. The main production material is aluminum;
• SuperSpacer is an American development that is increasingly being used in Europe. The frame is not hollow, it is formed on the basis of foam from a polymer material. The structure provides maximum protection from the cold and helps save energy. Flexibility does not impose restrictions on the configuration of window frames; they can be either classic rectangular or round.

Choosing a spacer frame is a guarantee that the window will last a long time and will provide reliable protection from the cold throughout its entire service life, and moisture will not accumulate between the layers of glass. Correct selection also affects the strength of the structure, its ability to withstand wind and impact loads without destruction or deformation that violates the geometry.

Test table for double-glazed windows with different spacer solutions

Single-chamber double-glazed window 4-16-4

Double-glazed windows with PVC spacer frames, imaginary and real advantages

2008

GLASS UNITS WITH PVC DISTANCE FRAMES

ADVANTAGES, IMAGINARY AND REAL

Before starting a conversation about the real advantages and disadvantages of double-glazed windows with spacers made of PVC, it is necessary to explain why suddenly in recent years the question of finding an alternative to traditional spacers made of aluminum or its alloys has become so urgent. Why did Lux ​​(Ekaterinburg) start searching for manufacturers and suppliers of PVC frames two years ago and have been producing such double-glazed windows for more than a year? Why did (Novosibirsk) re-equip one of its extruders to produce such products? Why is any research being done in this area at all?

One of the reasons is the increasing number of complaints from consumers (we are talking about consumers living in the central part of the Russian Federation and Siberia), who are dissatisfied with the appearance of condensation on the glazing during operation of window units, albeit in a narrow strip, flowing onto the window sill (Fig. 1).

Another reason is the tightening of regulatory requirements. According to SNiP “Thermal protection of buildings”, the minimum temperature of the internal surface of a window unit should not fall below +3 °C - at the design temperature of the outside air. Territorial building codes (TCN) for energy saving in buildings, put into effect in most regions of the Russian Federation, also contain similar and sometimes even more stringent requirements. This means that any buyer of a single-sash window (whether made of PVC or laminated wood), if frost or ice appears on the glazing and is dissatisfied with his purchase, can through the court have his purchase declared non-compliant with the requirements of current regulatory documents and demand its replacement with compensation costs incurred. Of course, there are no such processes on a massive scale yet, but there are already precedents and the trend is clear.

Manufacturers of windows of various designs are currently faced with the need to solve this problem: from PVC, laminated wood, aluminum. It must be said that a decrease in the glazing temperature in the so-called edge zones of double-glazed windows occurs in almost any climatic conditions, however, in areas with low outdoor temperatures (which include most of the territory of the Russian Federation), it manifests itself especially clearly. And if in Western Europe this problem is considered mainly from the point of view of energy saving - reducing heat loss through double-glazed windows in the edge zones (which in itself is not so significant in the heat balance of a building), then in the climatic conditions of the Russian Federation, sanitary and hygienic issues come to the fore requirements. In the cold season of the year, a decrease in the temperature of the inner surface of the glazing leads to condensation around the perimeter of the window, wetting of profiles and window sills (which is especially painful for windows made of wood), and at low outside temperatures - to freezing of condensate with the formation of frost and ice.

The question naturally arises: how to solve this problem? Should we switch to the production of window blocks with paired or separate sashes (glass plus a double-glazed unit) or look for ways to improve the temperature regime of the edge zones of double-glazed windows in single sashes?

Specialized magazines “Translucent Designs” (see No., No. 4, 2001, No. 1, 2005), “Windows and Doors” (No. 5, No. 10, 1999) have already repeatedly addressed various aspects of this problem.

The purpose of this article is to show with examples the real advantages and disadvantages of double-glazed windows with PVC spacer frames, the production of which has currently been mastered (Novosibirsk), Lux (Ekaterinburg) and a number of other enterprises.

In this regard, first of all, it must be noted that a complete solution to the problem of edge zones can only be complex: both through the use of spacer frames with low thermal conductivity coefficients, which include PVC, and by reducing convection in the interglass space.

In most publications on this topic, the solution to the problem is usually associated, first of all, with the material of the spacer frames. And in this regard, certain misconceptions have arisen that require clarification, since in some cases they lead to inflated expectations, in others to a lack of faith in the possibility of solving this problem as a whole.

Misconception 1. Spacers made of aluminum or its alloys used by most manufacturers of double-glazed windows are characterized by a fairly high thermal conductivity coefficient -   180÷220 W/(m oC). And it’s worth replacing them with frames made of stainless steel -   14 W/(moC) or PVC -   0.17 W/(moC) and the problem is solved. Reducing the thermal conductivity coefficient by almost 1000 times, for example when replacing aluminum with PVC, should have a corresponding effect. And in some articles this idea is carried out (for example, in the article “Two or Three”, “SK”, No. 4, 2001). However, unfortunately, not everything is so simple and unambiguous.

The temperature regime of double-glazed windows in the edge zones depends on a number of factors: the actual thermal conductivity of the spacer frames themselves, the thermal conductivity of the sealant around the perimeter of the double-glazed window, cooling of the part of the double-glazed window placed in the profile, and a decrease in the heat flow to the glass from the side of the room in the beading zone. But the most important thing is air convection inside the glass unit. It is the movement of air inside the air gaps between the glasses that leads to a lower glazing temperature in the lower zone (Fig. 2). And no matter how good the heat-insulating qualities the spacer frame has, it is impossible to solve the problem as a whole with a frame alone. But it is possible to alleviate the problem.

As an example, Fig. 3, Fig. 4 show the results of comparative tests of double-glazed windows of various design solutions with spacer frames made of aluminum and PVC installed in window blocks made of PVC profiles “VEKA” of the “SOFTLINE 70” series.

Analysis of test results shows that the increase in the minimum temperature of the inner surface of the glazing when replacing aluminum frames with PVC can be from 2.5 to 4.5 °C. The variation is due to the fact that double-glazed windows can be installed in a profile with different depths of the spacer frames (the smaller the depth, the more striking the effect) and the use of low-emissivity glass.

It should be noted that in single-chamber double-glazed windows with a low-emissivity coating of the inner glass, despite the use of PVC frames, it is still not possible to ensure the required temperature conditions (minimum glazing temperature not lower than +3 °C). The reason is convective heat transfer in the interglass space.

Similar results were noted when testing double-glazed windows manufactured using TPS technology.

Misconception 2: PVC frames age quickly when exposed to ultraviolet irradiation (UVR). PVC spacer frames are made from the same raw materials as PVC profiles. Accordingly, issues of durability, aging, color changes, etc. under the influence of ultraviolet radiation, elevated or low temperatures are exactly the same for both main profiles and spacer frames. Moreover, PVC profiles, unlike frames, are also exposed to precipitation, acidic or alkaline solutions (for example, when periodically washing windows). And if these profiles meet the requirements of GOST in terms of durability, then what can we say about the durability of spacer frames used in less severe conditions.

The test results of the IC SMIK "SIBSTRINEXPERT" NGASU, carried out on request, confirmed the absence of color changes and controlled indicators of PVC frames after complex cyclic impacts corresponding to 20 conventional years of operation.

Misconception 3. Double-glazed windows with PVC frames have a high linear expansion coefficient, which leads to increased deformation.

Reference values ​​for the coefficient of thermal expansion of some materials: steel  11÷1510-6, aluminum  24÷2710-6, PVC  7010-6 1/оС. Thus, with a temperature difference of 80 °C and a spacer frame width of 16 mm, the magnitude of possible temperature deformations will be: for steel  0.014 mm, aluminum  0.028 mm, PVC  0.09 mm. Even a simple comparison of the obtained figures shows that there is no reason to talk about large temperature deformations of double-glazed windows with PVC spacers.

Much more relevant in this regard are the deformations associated with changes in the volume of gas (air) filling the interglass space (Fig. 5). When the outside air temperature drops, the volume of gas in the space between the glasses decreases, and the outer glass in the double-glazed unit bends inwards (by the way, this phenomenon can also lead to the destruction of double-glazed windows when used in extreme conditions or transported at low outside temperatures). When the temperature rises, for example in summer, the volume of gas increases and the glass bends outward. And the greater the temperature difference between winter and summer (and most of the territory of the Russian Federation is characterized by a sharply continental climate), the greater these deformations. And accordingly, the sealants used must be able to compensate for these deformations (have certain elastic properties).

Misconception 4. Double-glazed windows with PVC frames do not provide airtightness due to poor adhesion of the polysulfide sealant. The results of testing the adhesion of the primary (butyl rubber) and secondary (polysulfide) sealing layers of double-glazed windows to PVC and glass show that sealants based on butyl rubber have fairly good adhesion to both glass and PVC (cohesive rupture - along the sealant). However, polysulfide sealants have really poor adhesion to PVC - the polysulfide sealant layer easily peels off from the PVC.

In this regard, several points should be noted. First, how important is the adhesion of the secondary layer sealant to the spacer really? If we talk about the deformations of a double-glazed window (see Fig. 5), then from the point of view of maintaining the tightness of the inter-glass space, first of all, the adhesion of the sealant to the glass is important. And if it is good, then the durability of the double-glazed window should not be affected by the presence or absence of adhesion of the sealant to the spacer frame. In this regard, weak adhesion of polysulfide sealants to PVC may rather affect some strength characteristics (although in this regard the influence of adhesion is questionable).

Secondly: in addition to polysulfide sealants, polyurethane-based sealants can be used for secondary sealing. These sealants have the same adhesion to PVC as to glass. Moreover, polyurethane sealants are also characterized by lower diffusion ability, lower water absorption, and better elastic properties. The transition from polysulfide sealants to polyurethane not only removes all issues of adhesion to PVC, but also increases the reliability of the glass unit as a whole.

Third. What you really need to pay attention to is the sealing of the connecting corners, with the help of which spacer frames are assembled (we are talking about the technology for manufacturing double-glazed windows using corner profiles for assembling spacer frames). If, when assembling a double-glazed window, the corners are inserted “dry” into the cavities of the spacer frames, then in the places where they are located the primary sealing layer practically does not work, since “holes” are formed in the corners for gas leakage from the space between the glass or the diffusion of moisture into the glass unit. In this regard, it is necessary to carefully comply with the requirements of GOST (clause 4.2.2) for filling all joints between frame elements with non-hardening sealant (butyl). This remark should also apply to traditional types of spacer frames.

Misconception 5. The heat transfer resistance of double-glazed windows with PVC frames increases significantly.

Unfortunately, it is not. The reduced heat transfer resistance of double-glazed windows with PVC frames does increase, but only by 4-6%. The reason is that the area of ​​action of the spacer frames is relatively small in relation to the total area of ​​the double-glazed window, and in addition, as already noted, replacing the frame material does not affect the convective heat transfer inside the interglazed space of the double-glazed window. The results of comparative tests of the reduced heat transfer resistance of double-glazed windows of various design solutions, presented in Table 1, confirm this conclusion.

Conclusion

The use of spacers made of solid PVC can significantly improve the temperature regime of double-glazed windows in the edge zones and, in combination with the recessing of double-glazed windows in window profiles, is able to ensure compliance with the requirements of SNiP for the minimum temperature of the internal surface in climatic regions with a design temperature of the outside air down to minus 30 oC. To further improve the temperature regime in the edge zones, including expanding the scope of application of single-chamber double-glazed windows with low-emissivity glass coating, it is necessary to reduce convective heat transfer in the inter-glass space.

Leading manufacturers of spacers

• Global Glass is an American manufacturer of double-glazed windows and components. There is a representative office in Russia.
• Lenhard – German manufacturer, developer of TPS technology.
• Edgetec is another North American manufacturer and the inventor of the Super Spacer technology.

You can easily find out about other manufacturers, especially domestic ones, on the Internet by entering the appropriate search query.

As you can see, spacers play a significant role in maintaining the integrity and efficiency of the glass unit. There are many types of spacers. Each has its own unique properties and they are all equally good. What type of spacer frames to choose depends on the needs of a particular consumer.

Buy a PVC spacer frame

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How to choose really warm windows?

• High-quality energy-saving glass with enhanced thermal insulation properties. Energy-saving glass has a special low-emission coating of silver ions, which reflects thermal radiation from batteries and radiators back into the room;
• The inert gas is argon. It allows you to slow down the air circulation inside the glass unit and reduces the cooling of the entire chamber. In X-ONE windows, which are produced on an automatic line, the glass chamber is completely sealed. Argon does not leave the chamber, its losses are no more than 1% per year;
• “Warm” spacer frame that prevents the edges of the glass unit from icing;
• The use of a one-piece bent frame in double-glazed windows ensures greater tightness and reliability of the double-glazed window.

Choose real warm windows with X-ONE double-glazed windows from the Russian Glass Company. Contact the company's partners, they will select for you an individual solution specifically tailored to your needs, and you will be sure that your windows fully meet the latest technologies.