Building energy conservation includes new construction (including alteration and expansion) of building energy conservation and energy-saving renovation of existing buildings. China has a building area of 40 billion square meters, most of which are not energy efficient.
The public building area of the country is about 4.5 billion square meters, of which public buildings (shops, office buildings, hotels) with central air-conditioning are 500-600 million square meters, and the energy consumption per unit area of public buildings accounting for 11% of the existing building area is about It is about 10 times that of an ordinary residential building, and it is called a large energy consumer.
Some public buildings have more than 20% of the building area, 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 door and window, and the tempered insulated glass energy consumption accounts for about 80% of the window area.
There are only two options for the energy-saving renovation of glass in existing buildings: one is to replace the original glass with energy-saving glass, and the other is to attach the original glass to the thermal insulation film for construction.
Types and functions of energy-saving glass
1. Coated glass: Coated glass is one or more layers of metal, alloy or metal compound on the surface of the glass to change the properties of the glass. According to different characteristics, it can be divided into heat reflective glass and low radiation glass.
Heat-reflecting (sunlight control) glass, generally 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 appropriate transmittance for visible light. Infrared has a high reflectivity and a low transmittance to ultraviolet light, so it is also called a solar control glass. Compared with ordinary glass, the shading coefficient is lowered, that is, the shading performance is improved, but the heat transfer coefficient is not changed much.
Low-emission (LOW-E) glass is a film consisting of a plurality of layers of silver, copper or tin or other compounds on the surface of the glass. The product has a high transmittance for visible light and a high reflectance for infrared rays. Good thermal insulation properties, due to the poor strength of the film, are generally made of insulating glass and not used alone.
2. Insulating glass: Insulating glass is composed of two or more glass frames made of aluminum hollow frame, sealed by cement or welding, forming a free space in the middle, which can be filled with dry air or inert gas, and its 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 little, and the heat reflection resistance to solar radiation is not improved much.
3. Composite of coated glass and hollow glass: including heat-reflecting coated hollow glass and low-emission coated insulating glass. The former can reduce the heat transfer coefficient and the shading coefficient at the same time, and the latter has a good light transmittance. Types and functions of architectural glass film
The architectural glass film is made by bonding high-quality polyester (PET) film and metal coating layer by vacuum magnetic spray coating process, which can provide excellent solar control functions for various types of glass. Architectural glass film is roughly divided into three. Big category:
(1) Building insulation glass film
Building insulation film is mainly used for energy saving. It is equipped with UV-blocking and safety explosion-proof functions. The building insulation film is divided into a heat-reflecting film and a low-radiation film.
The heat reflective film (also known as the solar control film) is attached to the surface of the glass to allow a certain amount of visible light to pass through the room. The high infrared reflectance IR and the low solar heat gain coefficient SHGC can keep the indoor temperature from rising in the hot summer. Too much, thus reducing the cost of electricity for indoor air conditioning.
Low-emission film (also known as LOW-E film) can transmit a certain amount of short-wave solar radiant energy, so that solar radiant heat (near-infrared) enters the room, and at the same time can more than 90% of indoor object heat sources (such as heating equipment) The radiated long-wave infrared (far infrared) is reflected back into the room. The LOW-E film can make full use of the outdoor solar short-wave radiation and the long-wave radiation energy of the indoor heat source. Therefore, it can be used as a heat preservation and energy-saving effect in heating buildings in cold regions.
(2) Building safety glass film
The main functions are safe explosion-proof, anti-theft and bulletproof. The film has good impact resistance (anti-explosive strength), 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 such as basic color, translucent, opaque and printed with various geometric patterns, opaque films such as one-way see-through film, translucent film such as matte film, relative to frosted glass and craft glass In terms of manufacturing, it has the advantages of durability, quick installation and low cost, and it can also change the decorative pattern whenever and wherever possible.
The Ministry of Construction and the National Development and Reform Commission stipulate that it is necessary to use safety glass for 11 parts of the building that require glass as the building material.
In the existing buildings, non-safety glass film can be upgraded to safety glass. The safety of laminated glass is better than that of tempered glass, which can avoid the spattering of glass bursting debris. Cost comparison between energy-saving glass and heat-insulating film
Case: 12MM tempered transparent glass for the curtain wall of an exhibition center hall. If it is replaced with 12mm heat reflective coated tempered glass, the material cost is 210 yuan / square meter, the old glass disassembly cost is 70 yuan / square meter, the total transformation The total cost is 280 yuan / square meter. If two LOW-E insulating glass with a thickness of 10 mm and a thickness of 12 mm are replaced, the material cost is 375 yuan / square meter, and the disassembly and assembly cost is 70 yuan / square meter, which is a total of 445 yuan / square meter.
The method of adding heat-reflecting film, the material cost is 100-130 square meters, the mounting cost is 30 yuan/square meter, the total is 130-160 yuan/square meter, and the cost of heat-reflecting film is 50% of the cost of heat-reflecting glass. %about.
The original glass is attached with a low-emission (LOW-E) film while being attached to the heat-reflecting film to obtain an energy-saving effect close to the LOW-E insulating glass. Six advantages of glass film modification
In the energy-saving renovation of building doors and windows and glass curtain walls, there are six advantages of the glass film:
(1) More economical. The tempered transparent glass or the colored glass-coated heat-reflecting film can save 50% of the total cost compared with the replacement of the heat-reflecting glass, and the rest can be analogized. For example, the original ordinary insulating glass is attached to the heat-reflecting film or the low-radiation film and then upgraded to Hollow heat reflective coated glass or hollow low radiation coated glass.
(2) Faster. The existing glass film is shorter than the old glass and replaced with a new glass, and the operation is simple.
(3) More environmentally friendly. Changing the glass will result in a large amount of broken glass construction waste, which will increase transportation and landfill costs, and the film can utilize existing glass to enhance its insulation and safety performance. It can also prevent indoor carpets, curtains, fabrics and paints from fading, effectively protecting indoor furniture, computer and other office equipment and extending their service life.
(4) More secure. The general thermal insulation film also has certain safety enhancement functions, and has the chip adhesion performance of the clip (glue) layer glass, and its safety is superior to that of tempered glass, and the safety of the professional safety film is stronger.
(5) Healthier. The mounting adhesive in the glass film contains a UV (ultraviolet) absorber that blocks 98%-99% of UV light.
(6) It is lighter. If it is replaced with insulating glass or hollow LOW-E glass, the total weight of the two glass plus hollow parts will be doubled or more, which will greatly increase the building load.
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