The glass selection guide for windows and doors sunroom①

In the installation and purchase of home windows, sunrooms, etc., if the importance of a single material is discussed, it is glass.

However, in the actual purchase of door and window glass, Jinan LIJIANG Glass found that there are still many "new purchasers who want to purchase the door and window glass" who do not have a clear understanding of glass purchases, not only do not understand their actual needs but also easily misled by merchants.

Jinan LIJIANG Glass continued to write an article on the cognition and purchase guide of home improvement doors, windows, and sunroom glass so that consumers can have a clearer idea when purchasing glass without stepping on the pit.

Content:

• The role of door and window glass
• Understanding glass properties
• Influencing factors of glass performance: product type, material, details
• The importance of workmanship in glass deep processing plants
• Glass selection according to local conditions
• About purchase requirements, budget, principles, order
• Summarize

1. The role of door and window glass

Glass products have an irreplaceable position in the field of construction. And with the development of technology and the continuous improvement of people's living standards, its functions and roles are also increasing:

The first generation of door and window glass, glass has been applied to windows. At that time, most of the window glass was cut into squares by hand and placed in wooden window frames, which mainly played the role of sheltering from wind and rain and lighting.
The shortcomings are obvious, the glass position is large and fragile, and it only has preliminary shielding and protection functions.

^{Figure 1 The window glass in wooden window frames 1}

In the second generation of door and window glass, the window material has evolved from a wooden structure to steel windows and aluminum alloy.

The glass has changed from the original small piece to the large piece, and the performance of shielding from wind and rain and lighting has been enhanced. However, because only the size changes, the glass does not bring performance blessings to the doors and windows.

^{Figure 2 The blue glass of door and window glass 1}

In the second-generation door and window glass, monolithic white glass and blue glass(tinted glass) are the mainstream

The third-generation door and window glass, its door and window representative has become the aluminum alloy sliding window and the inner and outer opening plastic steel window with a more reasonable structure.

Insulating glass is widely used in building doors and windows, so the most important performance of glass - thermal insulation is introduced. At the same time, with the development of tempering technology and the increase in glass thickness, the sound insulation performance and safety performance of the door and window glass is also greatly enhanced.

^{Figure 3 The aluminum alloy sliding glass door and window 1}

In the fourth generation of insulating glass, the production technology of doors and windows has entered a mature stage, and products such as broken bridge aluminum, aluminum-wood windows, and system windows are emerging one after another.

With consumers' increasing demand for improving the indoor living environment, glass production technology has also been significantly improved, and door and window glass has also been given more performance and requirements.

More thermal insulation, based on insulating glass, there are three glass two-chamber, vacuum glass, Low-E insulating glass, warm edge glass, rare gas insulating glass, and other options:

^{Figure 4 The three glass and two cavities of insulating glass windows 1}

More sound insulation, based on laminated glass or insulating glass, there are options such as three-glass two-chamber or insulating laminated glass:

^{Figure 5 The three-glass two-chamber or insulating laminated glass 1}

More transparent lighting, improve appearance, can use ultra-white glass original sheet for glass deep processing, larger single glass area, curved glass, curved glass, and other glass products:

^{Figure 6 The ultra-white glass of large insulating glass 1}

More privacy, based on insulating glass, there are frosted insulating glass, built-in louver insulating glass, art glass, and other options:

^{Figure 7 The built-in louver insulating glass 1}

Safer, you can use tempered and semi-tempered insulating glass, laminated glass, and its products:

^{Figure 8 The tempered insulating glass with 3C logo 1}

With more technology, there are also glass options with higher technology content such as self-cleaning glass, electro-dimming glass, thermo-dimming glass, and high borosilicate fire-resistant glass:

^{Figure 9 The electrically dimming insulated glass 1}

The Electrically dimming insulated glass has become a vital part of doors and windows.

2. Understand glass performance parameters 

Let's look at the main performance parameters of the glass.

△ Brain map of the main characteristic parameters of glass; image source public account Architectural Optics
For consumers, these performances can roughly understand these aspects:

2.1 Thermal insulation performance parameters

In the international industry standard "Design Standard for Energy Efficiency of Public Buildings", the building thermal insulation analysis of exterior windows is replaced by the value of the shading coefficient Sc with the value of the solar heat gain coefficient SHGC.
The SHGC value is defined as the ratio of the solar radiation part of the interior heat gain through glass doors, windows, or glass curtain walls and the solar radiation illuminance projected on the glass, doors and windows or glass curtain wall components in the wavelength range of solar radiation of 280 - 2500 nm.

The formula is: SHGC = τ + Nα (τ: solar transmittance; N: internal flux absorbing solar energy; α: solar absorption coefficient)

^{Figure 10 The Solar heat gain coefficient SHGC 1}

The smaller the index of the SHGC value of the solar heat gain coefficient, the less the outdoor heat enters the room through the glass, and the stronger the ability to block the penetration of outdoor heat, and vice versa.

Take the United States as an example. For cities like Los Angeles and Miami, which are hot in summer and warm in winter, we need a glass with a lower heat gain coefficient to block as much heat as possible outside; cities like New York and Philadelphia, which have mild summers and cold winters, need a glass with a lower heat gain coefficient. Glass with a higher heat gain coefficient is required to allow more heat to enter the room.

 ^{Table 1 The Common insulating glass photothermal performance parameters 1}

the far right is the solar heat gain coefficient SHGC, 3# / 5# refers to the position of the Low-e film layer

One article to understand the common photothermal parameters and calculation methods of insulating glass

As can be seen from the data in the above figure, the most effective way to improve the thermal insulation performance of glass is to add insulating glass into three-glass two-chamber, multi-layer Low-e film, or install the glass Low-e film on the outer layer.

2.2 Insulation performance parameters

The K value is the heat transfer coefficient code used at the beginning of the Chinese building energy conservation standard system, and the U value is the heat transfer coefficient code of other countries, which is used to measure the thermal insulation performance parameters of doors and windows (glass). K value is the main, K value / U value calculation method is the same, there are subtle differences in calculation standards, consumers only need to know what the heat transfer coefficient is).

Definition of heat transfer coefficient K value / U value: under steady-state heat transfer conditions, when the ambient temperature difference between the two sides is 1K, the heat passes through a unit area of doors, windows, or glass curtain wall in unit time.

The formula is: K value = Q / △T + A = q / △T 

[Q: heat transmission rate (W);

△T: Indoor and outdoor temperature difference (K);

A: Projected area (m²);

q: heat flux (heat flow per unit area) (W/m²)]

^{Figure 11 The heat transfer coefficient K values 1}

The lower the value of the heat transfer coefficient K value, the smaller the ability of the room to lose heat to the outside, and the warmer it is.

So in cold weather, we need a lower heat transfer coefficient. Therefore, the further north, the higher the heat transfer coefficient requirements in the energy-saving standard, the lower the value.

^{Table 2 The light and heat transfer coefficient of common insulating glass 1}

It can be seen from the data in the above figure that the most effective way to improve the thermal insulation performance of the glass is to add the insulating glass to three glass and two cavities, single-layer Low-e film, warm edge, or fill with rare gas and change the thickness of the insulating-layer glass. 

2.3 Light transmission performance parameters

The most basic function of glass windows is "lighting", that is, the ability of glass to transmit visible light, which is measured by the visible light transmittance Tv.

The higher the visible light transmittance, the better the natural lighting, the more transparent and the more comfortable living. However, it and the heat gain coefficient are a contradictory combination, and the two cannot have both. It is necessary to use different glass configurations according to the climate zone used to achieve a relatively harmonious unity.

^{Table 3 The visible light transmittance of some glasses}

The overall light transmittance of glass is related to the light t

The overall light transmittance of glass is related to the light transmittance of the original glass, the thickness of the glass, the number of layers, and whether it is coated. Ultra-white glass sheets are commonly used in home decoration to improve the overall light transmittance of glass. 

2.4 Sound insulation performance parameters

In some developing countries' industry-standard "Code for Measurement of Sound Insulation in Buildings" and the subsequent industry-standard "Measurement of Sound Insulation for Acoustic Buildings and Building Components", the weighted sound insulation Rw is used to measure and evaluate the sound insulation performance of buildings, and the unit is decibel. (dB).

European and American standards mostly use sound transmission level STC to measure, the values of Rw and STC are slightly different, and the STC value of the same glass is equal to or slightly lower than Rw.

^{Table 4 The weighted sound insulation Rw value of common glass 1}

The higher the weighted sound insulation Rw, the better the sound insulation effect of the glass.

From the above table and known data, these methods can effectively improve the sound insulation performance of glass: the insulating glass can be added to laminated glass, laminated insulating glass, double-laminated insulating glass, appropriate thickness of the insulating layer, or increase the thickness of single glass. The thickness of the interlayer, the use of different thicknesses of insulating glass, etc.

^{For more information about Jinan LIJIANG Glass insulating glass processing equipment and insulating glass processing accessories, please click here to learn more.}