Building energy efficiency includes new construction (including reconstruction and expansion) of building energy efficiency and energy conservation of existing buildings. China has 40 billion square meters of built-up area, most of which are not energy-efficient.
The total area of ​​public buildings in the country is approximately 4.5 billion square meters, of which public buildings using central air-conditioning (shopping malls, office buildings, hotels) are 560 million square meters, and the energy consumption per unit area of ​​public buildings that account for 11% of the existing building area is approximately It is about 10 times that of ordinary buildings. It can be called a big energy consumer.
Some public buildings have more than 20% of the total area of ​​doors and windows, and the energy consumption through doors and windows accounts for about 50% of the entire building. The energy loss through the glass accounts for about 75% of the energy consumption of the windows and doors, and the energy consumption of glass, which accounts for about 80% of the window area, takes up the first place.
The emphasis of building energy-saving renovation is on public buildings. The renovation of doors, windows and curtain walls is the key to building energy-saving. Among them, the transformation of glass is the most important task of energy-saving work.
There are only two options for the energy-saving glass transformation of existing buildings: one is to replace the original glass with an energy-saving glass, and the other is to affix the existing glass to the building's thermal insulation film.
Energy-saving glass types and functions
1. Coated glass: Coated glass is coated with one or more layers of metal, alloy or metal compound on the glass surface to change the properties of the glass. According to different characteristics can be divided into heat reflective glass and low-e glass.
Heat-reflective (sunlight-controlling) glass is usually coated with one or more layers of metal such as chromium, titanium, or stainless steel or a compound thereof on the surface of the glass, so that the product is rich in color and has suitable transmittance for visible light. Infrared rays have a high reflectivity and have a very low transmission rate to ultraviolet rays. Therefore, it is also called a solar control glass. Compared with ordinary glass, the shading coefficient is reduced, that is, the shading performance is improved, but the heat transfer coefficient is not changed much.
LOW-E glass is a thin film composed of a layer of silver, copper or tin or other compounds on the glass surface. The product has high transmittance to visible light and high reflectivity to infrared light. Good thermal insulation performance, due to poor film strength, is generally made of insulating glass and not used alone.
2. Insulating glass: Insulating glass is composed of two or more glass frames framed by aluminum hollow frames, sealed with glue or welding, forming a free space in the middle, which can be filled with dry air or inert gas, with a heat transfer coefficient U ratio. The single-layer glass is small and the heat preservation performance is good, but the shading coefficient SC is reduced very little, and the heat reflectivity to solar radiation is not improved much.
3. Composite of coated glass and hollow glass: including heat-reflective coated insulating glass and low-emissivity coated insulating glass. The former can reduce the heat transfer coefficient and the shading coefficient at the same time, and the latter has better light transmittance. Architectural glass film types and functions
The architectural glass film is made of high-quality polyester (PET) film and metal coating layer pressed and bonded by vacuum magnetic spraying technology. It can provide excellent sunlight control function for various types of glass. The architectural glass film is roughly divided into three. Category:
1, building insulation glass film
The main purpose of building insulation film is to save energy, with UV isolation and safety explosion-proof functions. This type of building insulation film is divided into thermal reflective film and low-radiation film.
Thermal reflective film (also known as solar control film) is attached to the glass surface so that a certain amount of visible light can pass through the room, high infrared reflectivity IR, and low solar heat gain coefficient SHGC. In the hot summer, the indoor temperature can not be increased. Too much, thereby reducing the cost of indoor air conditioning electricity.
Low-radiation film (also known as LOW-E film) can transmit a certain amount of short-wave solar radiation energy, so that solar radiant heat (near-infrared) enters the room, and at the same time it can be more than 90%% of the indoor object heat source (such as heating equipment) Long-wave infrared (far-infrared) radiation is reflected back into the room. The LOW-E film can make full use of outdoor short-wave solar radiation and long-wave radiation energy of indoor heat sources. Therefore, the use of heating in buildings in cold regions can achieve significant effects of thermal insulation and energy conservation.
2, building safety glass film
The main functions are safety explosion protection, anti-theft and bulletproof. This film has good impact resistance (anti-explosive strength), anti-stab strength, and UV blocking ability, high transparency or full transparency.
3, decorative glass film
The main function of this film is decorative, a wide variety of basic colors, translucent, opaque and printed with a variety of geometric patterns, opaque films such as one-way perspective film, translucent film such as frosted film, relative to frosted glass and craft glass In terms of manufacturing, it has the advantages of durability, quick installation, and low cost, and can also be used to change the decorative pattern anytime and anywhere.
The Ministry of Construction and the National Development and Reform Commission require that safety glass be used in 11 types of buildings where glass is used as a building material.
In the existing building, non-safety glass can be upgraded to safety glass after being laminated. The safety of laminated glass is better than that of tempered glass, which can prevent glass bursting and spattering from hurting people everywhere. Comparison of the cost of replacing energy-saving glass with insulation film.
Case: 12MM tempered clear glass for point-supported curtain walls in a hall of the exhibition center. If replaced with 12mm heat-reflective coated tempered glass, the material cost is 210 yuan per square meter, and the old glass disassembly and assembly cost is 70 yuan per square meter. The total cost is 280 yuan/square meter. If two LOW-E hollow glass with a thickness of 12 mm and a thickness of 10 mm are replaced, the material cost will be 375 yuan per square meter, plus the disassembly and assembly cost of 70 yuan per square meter, the total will be 445 yuan per square meter.
The use of retroreflective film method, the material cost is 100-130 square meters, the installation cost is 30 yuan / square meter, total 130-160 yuan / square meter, the cost of heat reflective film is 50% of the cost of heat exchange reflective glass %about.
The original glass is affixed with a low-emission (LOW-E) film at the same time that the heat reflective film is applied, and the energy saving effect of the LOW-E insulating glass can be obtained. Six advantages of glass film transformation
In the energy-saving renovation of building doors and windows and glass curtain walls, there are the following six advantages of the existing glass film:
1, more economical. It is necessary to save 50% of the total cost of existing tempered clear glass or tinted glass thermal reflective film than the replacement of heat reflective glass. The rest can be analogized. For example, the original ordinary glass thermal reflective film or low-radiation film is upgraded to Hollow heat reflective coated glass or hollow low emissivity coated glass.
2, faster. The existing glass film is shorter than the time required to remove the old glass and replace it with a new one, and the operation is simple and easy.
3, more environmentally friendly. The replacement of glass will generate a large amount of crushed glass construction waste, which will increase transportation and landfill costs, while the film can use existing glass to make it insulative and upgrade its safety performance. It can also prevent the fading of interior carpets, curtains, fabrics and paints, effectively protect indoor furniture, computers and other office equipment, and extend its service life.
4, more secure. The general insulation film also has a certain safety enhancement function, and at the same time, it has the debris sticking performance of the clip (glue) layer glass, its safety is superior to the tempered glass, and the safety of the professional safety film is stronger.
5, more healthy. The mounting adhesive in the glass film contains a UV (ultraviolet) absorber that blocks 98% to 99% of the UV rays.
6, more light. If the replacement is hollow glass or hollow LOW-E glass, the total weight of the two pieces of glass plus the hollow part can be doubled or more, which will greatly increase the construction load.
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