Since the 1980 s, aluminium windows and wooden window have been largely eliminated in China in copper window. In just a few years, they have become the de facto standard for exterior windows of new buildings. However, since the 1990 s, plastic-steel windows made of instrument frame improved strength have exposed their heads and feet, the country promotes the use in some areas, so some people advocate that plastic steel windows, as "green materials", will become the new mainstream, and then occupy the market share of all other windows including all kinds of alloy windows.
Will plastic-steel windows really become the new overlord?
Let's make a comprehensive comparison with aluminium windows.
Are aluminum alloy doors and windows eliminated plastic steel doors and windows, or plastic steel doors and windows changing destiny against the sky?
I. Durability: Aging and Eternity
as we all know, plastic is a synthetic substance with low hardness and natural aging, while the surface of aluminum alloy material is aluminum oxide (that is, the composition of sapphire, whose hardness is second only to diamond). After decades of research, the aging quality resistance of plastics has been greatly improved. However, improving does not mean stopping aging. As long as we compare the plastic and aluminum alloy surface installed several years ago, it is not difficult to find the defects of plastic in aging and abrasion resistance. Of course, the degree of this defect is relatively small at present.
In addition, aluminum alloy profiles have been specially treated as "aging" during their processing to eliminate built-in stress; however, there is no such process in the production engineering of the steel as the stress material of the plastic steel window. As the predecessor of plastic-steel windows, the copper window was eliminated precisely because of the existence of built-in stress, which led to long-term deformation and difficulty in normal opening. Plastic-steel windows also inherited this consensus problem.
II. Tightness: heat insulation and sound insulation
just for sealing, the same push-pull plastic steel window and aluminium windows are basically the same due to the mature technology. However, some people always compare the thermal conductivity of the two, thus pointing out that the thermal insulation performance of alloy windows is poor. Due to the excellent thermal conductivity and conductivity of aluminum in metal, it is inevitable to suffer losses.
But is it true? Let's look at the specific situation of heat exchange between the room and the outside world.
First of all, most of the heat exchange is completed by air convection. No matter in winter or summer, the opening and closing of windows play a decisive role in indoor temperature (at the same time, because people are cold, the feeling of heat is due to the rate of heat loss from the skin rather than the specific temperature, and the tightness of windows becomes the key to "hot and cold");
secondly, heat radiation is also an important way of heat transfer. In this regard, silver reflective aluminum will be more resistant to heat radiation than plastic of any color, and the color of glass and whether the room is facing light is also crucial;
finally, the heat conduction of the form. Is window frame important when conducting heat? On the contrary, because the cross-sectional area of aluminum alloy or plastic only accounts for 5 ~ 7% of the exterior wall of the room and 1% of the surface area of the room, the influence on the total amount of heat conduction is negligible. However, the gap between the two is more negligible than the decisive role of heat convection. There is no need to worry about how much more air conditioning electricity you will pay for aluminium windows (in fact, no matter how good the "health air conditioner" is, it cannot compare with the flow of natural wind.
If you are willing to let the room have the opportunity to get in touch with the fresh outdoor air every day, I am afraid that the "how much electricity do you save every year" claimed by some advertisements can only be a castle in the air).
Similar to heat insulation, if you want to get the best sound insulation effect, you 'd better install double-layer glass windows: the sound insulation effect of air in the interlayer is much better than that little plastic on the window frame (steel is hidden inside).
III. Environmental Protection: Who is the green material?
Before blindly following the advocacy about "green" materials, let's compare the life course of the two windows.
Acquisition of raw materials:
both of them are produced in large enterprises in the industrial zone. One is the smelter producing aluminum ingot, the other is the chemical plant producing plastics and the steel plant producing steel sections.
Here, some pollution is inevitable at present. But it is still far from the city.
1. Form production: the assembly of plastic parts and the extrusion molding of aluminum profiles are basically free of pollution.
2. Form use: there is basically no pollution.
3. Form disassembly and modification: just like the "white" pollution of those plastic lunch boxes, the instrument frame, which is also plastic and difficult to age, will become the "eternal" pollution for a hundred years; while aluminum alloy can be repeatedly processed and used, and even has the economic value of recycling!
In Europe and America, recycled aluminum is a mature industry. Even under the domestic technical conditions, the recycling price of aluminum alloy doors and windows disassembly is about 13-15 yuan/kg, with a value retention rate of over 70%, it is the highest among all building materials at present and is a typical reusable material.
If you want to change the shape of the window, for example, install ventilation equipment, car window shade or window air conditioner for a room, aluminium windows can also be implemented on site, and plastic steel windows have to be thrown away again, adding pollution.
In this way, the name of "green" of plastic-steel windows seems to be somewhat unworthy.
IV. Convenience: Who is more convenient to install and design freely?
Due to the singleness of aluminium windows materials, its installation is convenient and fast, and it can simultaneously meet large-scale mechanized construction and manual installation as small as one household, and can achieve satisfactory results (excluding the "bridgehead army" with poor technical quality).
In contrast, plastic-steel windows can only be completely installed after being produced by large manufacturers. Although this eliminates some inferior installation projects, it also loses the convenience of installation, flexible and possible promotion to non-film users and the vast rural areas.
On the other hand, the factory assembly of plastic-steel windows also makes the architectural design lose freedom to a certain extent.
In today's increasingly pursuit of individuality, the design with characteristics but no considerable demand means extremely high cost for plastic-steel windows, or it cannot be produced at all.
In fact, this is a fundamental reason why "industrial assembly building" has not been popularized and has become the mainstream in Europe and America for nearly a century-as the residence in which people live, personality, change is necessary.
Obviously, with the need of national energy conservation and emission reduction and the arrival of high-performance system aluminum alloy doors and windows, plastic steel doors and windows will be gradually eliminated by the market.
