- History of French windows
- Design features of French windows
- Characteristics of French windows
- Smart glasses in double-glazed windows
- At the end
In this Article: French Windows – History; features of French windows; positive and negative characteristics of windows and doors; panoramic windows with smart glasses; finally – tempered glass, heating and legal aspects.
In a few decades, if the plots of science fiction films are true, the walls of our houses and apartments will cease to be impenetrable – while maintaining their load-bearing functions, they will allow household members to observe city views without going up to the windows. However, the idea of transparent walls, if necessary, was taken from real life by science fiction writers – translucent structures that occupy the entire wall still exist today. Their common name is French windows..
History of French windows
Towards the end of the 7th century, French architects used a new idea in their projects – window openings that completely occupied one wall. This decision was justified from the standpoint of the architecture of the Renaissance, because made it possible to increase the illumination of the rooms behind the huge windows to the limit, while the sun’s rays even penetrated into the corridors, previously illuminated artificially, with the help of oil lamps (there was no electricity at that time). Windows of that era differed from modern ones in that they did not have rare and very expensive glass, therefore the first French windows were more likely French doors, because consisted of two swing or sliding doors, consisting of a metal frame sheathed with boards. By the way, it is for this reason that the translucent structures of French windows – it is under this name that they are known in Russia – in Europe it is French doors that are called (fr. portes-fenetres).
With the expansion of the production of the glass industry, the openings of French windows began to be closed with glass, their design began to contain blind windows and doors leading to a terrace or balcony.
French windows, also called panoramic windows, are still popular in high-rise and private houses in France and Italy. In Russia, panoramic windows were included in some architectural projects of Stalin’s four and five-story buildings, erected in the 50s of the last century..
Design features of French windows
Plastic and wooden frames for French windows-doors are divided into several sections, glazed independently of those located in the neighborhood – this measure allows you to strengthen the frame, which is necessary, since its area is very large. It is possible to do without sectional breakdown only if the frame is made of an aluminum profile, and the insulating glass units are made of tempered glass.
If we compare the design of these windows with ordinary window frames, then the complete absence of an impost is striking – a vertical lintel between two window sashes. This feature is associated with the purpose of the French window, which acts simultaneously as a door, therefore, when opened, its sashes must completely free the overlapping opening, as if they did not exist. To comply with this condition, the sashes are connected to the frame with a shtulp connection or are installed on a frame made of a special design profile – mono-, double- or triple-rail, which allows the sash to move to the side when opening. The thickness of the glass unit depends on the width of the profile (the largest is 32 mm), the dimensions (the largest is 3×3 m) and the weight of the sash (the largest is 400 kg).
As mentioned above, French windows are at the same time doors and such door-windows installed in openings of a large area and separating a room from a terrace or balcony are called “portals” – an impressive glazing area, especially in the absence of division into sections, opens a panoramic view. visually combining the room and the landscape outside its window into a single whole.
Sashes of French windows are most often arranged as sliding, less often swinging and very rarely – in the form of folding doors (books or accordions). The last type of doors is convenient only for portals between a room and a heated loggia, since it is almost impossible to provide full thermal insulation between several leaves.
Characteristics of French windows
Maximum insolation (natural illumination) of the room is the first advantage of panoramic windows. The second advantage is the visual expansion of the room area, because replacing the wall with transparent glass blurs the border between the room and the area adjacent to the house. The third advantage is present if there are attractive views outside the French window, for example, a park area or an unobstructed cityscape. Accordingly, if such a window goes into a “well” between high-rise buildings, there is no point in creating it.
In turn, French windows have disadvantages:
- high cost – from 12,000 rubles. per m2, moreover, the price of a French window will increase when a thermo-reflective film, double-glazed window and other additional options are used in the construction that increase the performance of these windows;
- the more “blind” segments in the frame and the higher the floor where the apartment with French windows is located, the more difficult it is to clean them. Due to the large area of glass, these windows will quickly get dirty on the outside and you will have to hire industrial climbers to clean;
- a significant area of the window opening creates a number of problems associated with overheating of the room in summer and its strong cooling in the cold season, despite the special design of the profile forming the frame and double-glazed windows. Intelligent heating, sun protection and forced ventilation required.
The operation of French windows is associated with a certain degree of psychological discomfort – if they are installed in high-rise apartments, despite the presence of tempered glass, it will not be easy to be close to them. It is necessary to carefully consider the issues of shielding such windows using blinds, roller shutters or special glasses – electrochromic or, otherwise, smart glasses.
Note that tinted windows are effective only in the daytime, while at night the inhabitants of apartments with tinted French windows may find themselves in the position of participants in the reality show “Behind the Glass” – from the inside, under artificial lighting in the evening and at night, the double-glazed windows look opaque, however outside the whole room behind them will be clearly visible.
Smart glasses in double-glazed windows
Among the usual means of shielding glazed openings, smart glasses are the most interesting. double-glazed windows, where they are inserted, do not need any additional curtains. The composite composition of “smart glasses” allows you to control the degree of their transparency, changing the light transmission at the touch of a button.
Today, there are three ways to obtain smart glass, differing in the interlayer between the glasses, which can consist of suspended particles (SPD), polymers in liquid crystal form (LCD) and electrochromic materials. When creating panoramic windows, electrochromic materials are usually used – consider them in more detail.
Electrochromic glass consists of two glasses, on the facing sides of which a thin and transparent electrically conductive layer is applied, an electrochromic layer about one millimeter thick is placed between them. The layer of electrochromic materials has a gel-like consistency, it is chemically neutral, i.e. does not react with the environment and does not emit any chemical substances into the atmosphere if the integrity of the outer layers of triplex glass is violated.
Most often, electrochromic smart glasses are made by placing a laminating film between two sheets of glass or polycarbonate. There are three types of such films:
- ethylene vinyl acetate (EVA), which adheres equally well to glass and plastic. Its advantages lie in the low cost of both production and the finished product, however, there are serious drawbacks – the electrochromic glass obtained on its basis is slightly cloudy, over time it acquires a yellowish tint. The disadvantages also include the tendency to displacement at high humidity and low temperatures, which leads to the formation of delamination inside the laminated glass;
- polyvinyl butyral (PVB) has high adhesion to glass, it adheres worse to plastics. At a higher cost compared to EVA-triplex, electrochromic glasses produced on its basis have higher quality characteristics – minimum turbidity, resistance to low and high temperatures. Lack of PVB-glasses – in conditions of high humidity, laminated glass may delaminate;
- thermoplastic polyurethane (TPU), has high adhesion to glass and to plastic in equal measure. Positive characteristics – there is no turbidity, complete immunity to high and low temperatures, mechanical stress, and the degree of humidity. The disadvantage is that compared to the two previous types of smart glasses, it is the most expensive, but the production of this triplex is also expensive. Among the three types of “smart glasses” TPU-triplex has the highest performance.
In addition to variable light transmission, smart glasses have high performance in terms of heat and sound insulation, thanks to their construction in the form of a sandwich and an inner polymer layer. To change the transparency of such glasses, a power supply with a voltage of 1.5 to 2.5 W is required, the transparency is controlled by a remote control or a switch. When the button is pressed, the change in the transparency of the glass begins along the perimeter, gradually moving towards its center – it takes 2-10 minutes to completely darken, and 4-15 minutes to brighten.
The main disadvantage of smart glasses is their cost, which seriously affects the total price of French windows – a square meter of such glass will cost the buyer from 35,000 rubles. and higher.
At the end
Each sash as part of a French window has a significant weight, most of which falls on a double-glazed window made of thick (6 mm and more) tempered glass – especially strong and high-quality fittings are needed, it is best if the sashes are sliding (sliding with an offset) on a roller run … Glasses of thinner thickness and, moreover, not tempered ones, cannot be used in double-glazed windows of panoramic windows – in a strong wind they can crack and fall out, moreover, they create a danger of falling out of the window for household members. At the same time, tempered glass will withstand significant mechanical stress, it is extremely difficult to break them.
In winter, being next to French windows, in comparison with conventional translucent structures, is noticeably colder, due to their large area. Since a mounted heating radiator, due to lack of space, cannot be installed under such a window, it will be necessary to install a warm floor or a heating convector built into the floor along the window along its entire length.
And finally, the legal aspects. Problems with the law will not arise if a French window is installed between the room and the balcony (loggia), but – before demolishing the wall between these rooms, make sure that this wall is not load-bearing! Demolition of load-bearing walls is strictly prohibited, as it will weaken the structure of the entire building! As a rule, the external wall of the loggia and, of course, the fencing of the balcony of the bearing functions, do not perform, however, it will be extremely difficult to install French windows instead of them on legal grounds, because permission from a number of government agencies will be required, and the likelihood of refusal is high – any changes in the facade architecture of buildings are not allowed by law.