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建筑幕墙一直是公共建筑和中高档住宅建筑外墙的主要装饰手段。虽然国标《建筑幕墙》（GB/T21086)对幕墙的水密性能提出了要求，并在附录D中给出了现场淋水实验方法，但在幕墙结构设计时，设计师还是习惯于考虑结构安全，重视结构强度设计和计算，而对于幕墙的防雨水渗漏设计和应采取的必要措施重视不够，使渗漏成为建筑幕墙常见的问题之一。
特别是降雨量和基本风压大，经常遇到台风袭击南方沿海地区，幕墙渗漏现象更加普遍，造成保温层失效、室内墙面产生湿斑、霉变等。因此当保温材料具有一定的吸水性时，在幕墙和保温层间设置防水层是非常必要的。为使保温层中因施工时或结露时形成的水汽能及时排出，防水材料选用防水透气膜是比较合适的。
防水透气膜由高性能材料复合而成，具有纤维交错排列的微孔结构，孔径小而均匀，可以使水气自由通过，但凝结成水后无法再穿透，从而保证建筑物内干燥（缺乏水分）舒适，同时避免凝结的水露破坏建筑物屋顶和墙体，以及损坏室内物品。
下面来分析下结露产生的原因：
1.空气中包含无色的水汽，通常我们用潮湿度进行衡量 (RH%)；
2.空气的温度越高，包含的水汽越多；
3.当温度降低时，空气无法包含原有的水汽；
4.空气温度越低，潮湿度升高，当潮湿度达到100% 时, 水汽凝结成液体,，结露现象就发生了, 这时的温度, 称之为凝结点；
5.只要建筑物内的热空气挥发接触到温度较低的屋顶和墙体，结露现象就会发生；
6.当结露现象发生时，就会在屋顶或墙体表面形成水滴。水滴被建筑物吸收，从而破坏墙体和屋顶结构，或者滴落，损坏建筑物内的物品。因此，轻钢和木结构别墅围护结构正确设计安装呼吸纸显得尤为重要。
防水透气膜的使用注意事项：要想防水透气膜具有良好的防风防雨的性能，正确的安装是关键：
1、防水透气膜的搭接方式高处的防水透气膜搭接在外部，低处的防水透气膜搭接在内部，从而能够让高处的水透过重力作用顺利排出建筑外。
2、拐角处的防水安装十分重要。转角处在使用钉固定之前要提前粘贴高分子防水丁基胶带，因为丁基胶带即便被钉子穿透，只要钉子未拔出，穿孔处仍然是防风防水的。
窗口和门口处的安装：窗口和门口处的防水透气膜密封工作要从下往上做，高出胶带在外，低处胶带在内；纵向胶带在外，横向胶带在内。在窗户底部两个角要先使用防水胶带呈45°角，用防水胶带密封，然后再在外侧和纵向使用防水胶带密封。
要想建筑内部的环境干净整洁，舒适良好，最好的方式是安装保温棉和防水透气膜。安装保温棉和防水透气膜不仅能够提高建筑物的节能效应，还能够提高建筑物内部的空气质量，减少传统建筑渗漏发霉的现象。是现代建筑的绝佳选择。
Breathable Membrane
The curtain wall has always been the main decoration means for public buildings and the exterior walls of middle and high-end residential buildings. Although the national standard (GB/T21086) on the building curtain wall has put forward requirements about building water tightness, and the water spray test method has been given on appendix D, but in curtain wall structure design, architectural designers still put more attention on the design and calculation of structural strength, cause this is the key factor about residential safety. The less attention paid on building water tightness design and necessary measures makes the curtain wall leakage problems one of the most common ones nowadays.is used to consider structure safety, attaches great importance to the design and structure strength calculation, to prevent leakage of rain curtain wall design and the necessary measures should be taken seriously enough, make leakage building curtain wall is one of the common problems,especially in places with heavier rainfall and stronger wind pressure.
In southern coastal areas where typhoon often occur, the curtain wall leakage phenomenon is more common, resulting in insulation failure, wet spots, mildew, etc..Therefore, if the thermal insulation material has certain water absorption rate, it is very necessary to set a waterproof layer between the curtain wall and the thermal insulation layer,in order to make the moisture accumulated inside the insulation layer discharge out in time. The house wrap is an common waterproof layer people often use for waterproof and breathable use. 
Breather Membrane
Waterproof Breather Membrane is made of high performance composite materials.The microporous structure of the fiber staggered has small and uniform aperture. The pore can let the water vapour inside go out freely, but unable to let the condensed water on the membrane penetrate in, thus ensures the building dry (a lack of moisture), and avoids condensation water to cause some problems inside the roof and wall or even damage the interior furniture.
Roof Membrane
Now lets learn about condensation:
1. The air contains colorless water vapor, which is usually measured by humidity (RH%);
2.The higher the temperature of the air, the more water vapor it contains.
3.When the temperature drops, the air can't control the original water vapor, which will turn to liquid water.
4. The lower the air temperature is, the higher the humidity is. When the humidity reaches 100%, the water vapor condenses into liquid, and the condensation phenomenon occurs.
5. As long as the hot air inside the building volatilizes and contacts the roof and wall with lower temperature, condensation phenomenon will occur;
6. When condensation occurs, water droplets will be formed on the roof or wall surface.Water droplets can be absorbed by the building, which will damage the wall and roof structure, or they will drip and damage the things inside the building.Therefore, the correct design and installation of light steel and wood structure villa contains the house wrap roof membrane.
House Wrap
Precautions for using of house wraps: correct installation is the key to ensure good of waterproof and windproof performance of house wraps. 
1.The House Wrap upper side is put outside on the laps, while The House Wrap lower side is put inside on the laps. This kind of lap will successfully let the condensation water drip out of the building by gravity action. 
2.the corner waterproofing: installation on corners is very important.Before the corner is fixed with nails, the polymer flashing butyl tape should be adhered in advance, because even if the flashing butyl tape is penetrated by nails, as long as the nails are not pulled out, the perforation is still windproof and windproof.
3. Installation on windows and doors: the house wrap sealing work on windows and doors should be done from bottom to top, higher tapes is installed outside and lower tapes inside;Longitudinal tape outside, transverse tape inside.The corners of the window sill should be adhered with two pieces of flashing butyl tape just at the corner part with a 45° angle in advance, then sealed with flashing butyl tape again on the outside.
Waterproof Membrane
The best way to make the inside room clean and comfortable is to install insulation and waterproof breathable membrane. The installation of insulation and waterproof breathable membrane can not only improve the energy saving effect of the building, but also improve the air quality inside the building and reduce the mildew and leakage phenomenon which usually appear in traditional building.Waterproof Membrane is a perfect choice for modern architecture.
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