What is the facade glazing coefficient?

Anyone trying to maximize the comfort and energy efficiency of their building must understand the facade glazing coefficient. This coefficient, also known as the window-to-wall ratio, expresses how much more glass is used on a facade relative to opaque materials like concrete or bricks.

To put it simply, a facade with a higher glazing coefficient has more glass in relation to its total surface area. This influences how much heat is retained or lost in the building as well as how much sunlight enters it. Extensive glazing can result in greater heat gain in the summer and heat loss in the winter, even though it can also provide panoramic views and natural light.

When designing a building, architects and builders pay close attention to the facade glazing coefficient in order to balance the requirements of energy efficiency, environmental impact, and aesthetics. Glass-to-solid material ratios can be changed to affect solar heat gain, daylight penetration, and overall building insulation, among other things.

The maximum glazing coefficient permitted by building codes is frequently governed by regulations and standards with the goal of promoting sustainable practices and reducing energy consumption. By following these guidelines, buildings can meet both functional and aesthetic requirements while achieving optimal thermal performance.

The notion of how much more glass a building’s facade has in comparison to solid materials like brick or concrete is examined in the article "What is the facade glazing coefficient?" on "All about the facades of the house." This coefficient shows how well architectural design balances energy efficiency, natural light, and aesthetics. Knowing this ratio enables architects and homeowners to optimize energy use for lighting, heating, and cooling while maintaining comfortable interior spaces. The environmental impact and livability of a building can be greatly impacted by selecting the appropriate glazing coefficient, which takes into account various factors such as climate, orientation, and building purpose.

Normalized heat transfer resistance

This coefficient is crucial for figuring out the building’s energy efficiency, heating, and general comfort level. Since glass doesn’t retain heat well, adding more glazing to the facade will inevitably raise the cost of heating the building and, consequently, operating expenses.

In SP 50.13330.2010 "Thermal Protection of buildings" SNiP 23-02-23, updated edition, the normalized heat transfer resistance of various structures is provided according to the building’s purpose and the degree of the heating period D, the value of which is established by the construction’s geographic location and the corresponding formulas provided in the joint venture.

On the coefficient of glazing facade

The ratio of the area of light apertures to the total area of the building’s external fence, including light openings, is known as the building’s coefficient of glazing.

F is equal to AF / (AW + AF),

In which Af is the square meter area of windows and balcony doors;

AW: The outer wall area, measured in square meters

The coefficient coefficient is denoted by the letter f.

They count all of the building’s perimeter walls (ends and longitudinal walls) when calculating the fence area.

The building’s energy passport contains information on the building’s energy efficiency, which is determined by the coefficient of glazing. This information is crucial for selecting the window filling design.

When the facade’s coefficient for residential buildings is less than 18% and 25% for public buildings, respectively, choose window fillings that have a higher heat transfer resistance than what is necessary.

R0 ≥ Rreq.

The window filling is chosen in accordance with the resistance to heat transfer (R0) mentioned above if the facade glazed coefficient is greater than the given values.

°C × day – R0 ≥ 0.51 when D ≤ 3500;

When °C × day – R0 ≥ 0.56, 3500 ≤ D ≤ 5200;

When °C × day – R0 ≥ 0.65, and 5200 ≤ D ≤ 7000.

The resistance of windows, balcony doors, and lanterns to heat transfer mentioned above

The heat transfer resistance value for double-glazed windows filled with inert gas, which currently have the best indicators, is not included in this table.

The temperature of the inner surface of the glass

In accordance with the norms, the temperature of the inner surface of the glass of TSI windows of residential and public buildings should be at least +3 ° C. Failure to comply with this standard will lead to condensation on the glass of moisture, ice in frost, the appearance on the slopes of mold due to the position of the dew point on the inner surface of the glass or inside the double-glazed window. Prevents this phenomenon the correct selection of the design of the double -glazed window. With relative humidity in a living room 60% and air temperature 20 ° C, the glass temperature should be not lower than 12 ° C, otherwise the glass will “cry”.

The following formula is used to calculate the temperature indicator:

TSi = DT – tint;

Where D t is the temperature differential between the interior glass surface and the room’s temperature, the value is computed using formula (4) from SP 50.13330.2010 "Thermal Protection of buildings" SNiP 23-02-2003, updated edition.

You must select a different window design with a high value of the aforementioned heat transfer resistance if the computation result is less than the necessary value.

Of course, if the home has traditional windows, these computations shouldn’t worry the owner. But, if the owner is unfamiliar with contemporary architecture and has a lot of glass surfaces that transform light, he needs to understand how the layout and amount of glazing impacts heating costs.

It is a fact that heat loss through translucent structures is 6–7 times greater than heat loss through insulated walls and 9–10 times greater than heat loss through the house’s insulated roof.

Types of panoramic glazing

Technologies currently in use for facade glazing:

1. The cold facade – the air gap between the glazing and the wall acts as a heat insulator (classic glazing).
2. Double facade – glass is hung with a gap from 20 cm to several meters from the main glazing. The air is diverted from the room to this gap, where it is mixed with cold air coming from the outside.
3. Structural facade – glazing by bindings of a special design, invisible from the outside.
4. Planning system (or spider glazing) – glazing without bindings, consisting of glass panels, carrying subsystems and fasteners.

Panoramic glazing is the facade glazing technology used in the double facade, structural facade, and planar system.

Structural facade glazing

The external glass in the structural glazing system is larger than the internal glass, and aluminum bindings that close the frame are situated from the side of the room. Tempered glass is used for glazing, and glasses are bound together with silicone sealant, which detects loads on two or four sides of the glass packet.

Reliability in preventing moisture intrusion into the building is a feature of silicone sealant, which also exhibits resistance to temperature changes.

The sealant can be painted colorless or with a glass tint. The system is dependable and permits extensive facade glazing; however, it necessitates perfect frame rigidity and precise construction, as the spaces between the glasses should not be wider than one or two millimeters. The glazing panels are standard size, measuring 1.5 by 2.5 meters.

Planning system

The newest and most efficient glazing system is the planar system, which is particularly well-liked by architects. Pilkington, a UK-based company, developed a unique system of tension structures and mounting mounts without bindings approximately forty years ago.

The technology enables you to design transparent structures in any shape and size; the only prerequisite for horizontal structures is a three-degree inclination to facilitate water drainage. The maximum height for supporting structures is 8 meters, and for suspended structures, it is 23 meters. There are no restrictions on the width of this type of glazing.

Currently, a great deal of businesses worldwide are involved in the design and installation of planar glazing. Each business creates its own mechanisms for attaching glass panels, as well as its own supporting systems and glass mounting hinges. The cost of the system as a whole goes up since nearly every object is calculated and a unique design is made.

Single-hardened glass, multilayer glass that is externally hardened, triplex windows that are internally hardened, or double-glazed windows can all be utilized in a system that uses an inert gas or a low-emission glass cover that is inside the glass packet. Such transparent structures’ indicators line up with the best double-glazed windows’ resistance, which is 0.8 m2 · °C/WT.

Two types of panel fastening have emerged: those with bolts integrated into multi-layer glass and those without through holes. In the latter instance, the bolts are put in place during the manufacturing of the double-glazed window at the factory. During installation, silicone sealant is poured into the spaces between adjacent panels.

Every fastener in some systems is made of steel, and there may be glass separators.

Planar glazing can be fastened using one of three methods, all of which have positive differences:

• The supporting beam with the equipment system – due to the large number of standard beams and equipment elements, the system is most economical;

• The system of equipment with cables – has a lightweight and as transparent as possible;

• curved string equipment – is characterized by a quick installation and medium price;

The pluses of panoramic glazing

Against the backdrop of urban development, panoramic glazing of any kind stands out visually and draws attention in particular if tinted glass is used.

Instead of using internal glass, panels made of metal, ceramic, or plastic can be used, which will give the structure a unique look and make it truly remarkable. The primary benefit of panoramic glazing is the expressiveness of the facade. Furthermore, the benefits of systems include:

• Durability.
• Repayable.
• Good sound insulation.
• Resistance to negative weather factors.
• Resistance to high and low temperatures.
• Efficiency.

Planar glazing systems can be installed from the inside or the outside of buildings, and installation is typically done from the bottom up in various structural systems. Glazing installed internally contributes to further cost savings when building forests.

If the facade appears to be a monolith made of glass from the outside, the supporting structures within have an industrial-style spatial frame made of a web of cables.

Cons of panoramic glazing

The primary drawback of panoramic structures is that they increase operating expenses, particularly those related to heating, and decrease building energy efficiency.

• High price.
• Individual complex calculation of each design.
• The requirement of high professionalism of performers during the assembly of the structure.

The window-to-wall ratio, or facade glazing coefficient, expresses the proportion of a building’s exterior wall surface that is made up of windows as opposed to solid wall materials. It is essential to a building’s aesthetics and energy efficiency.

Architects and builders can better balance insulation, heat gain, and natural light by being aware of this coefficient. More windows with a higher coefficient could result in an increase in natural light as well as heat gain or loss in warmer or colder climates.

The secret to energy-efficient designs is striking the right balance. In order to reduce heat transfer and improve comfort and sustainability, low-emissivity coatings and insulated glass units are two examples of the solutions provided by modern glazing technologies.

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