Windproof and Waterproof Performance of House Wrap
House Wrap was introduced to the construction market in the 1980s.For the past 30 years, the influence of house wrap on energy saving has always been the concern of some research and testing centers.Although house wrap does not need much energy for producing, the energy savings caused by this product is considerable.They can save energy using of the house by producing a good air barrier.A study of 2,000 people found that house wrap could only store energy inside a house for seven to 54 days.(Franklin institute 2000).This newspaper covers the performances of house wrap, including laboratory and field tests.A high frequency concern is still the wind resistance performance of house wrap.In addition, the change of the standards for the using of house wrap have also drawn people’s attention.
In 1970's, the energy crisis triggered widespread concern about energy-saving products in the construction industry.One of such products is waterproof membrane.The main function of the waterproof membrane is its wind-proof and energy saving performance. But in addition to this performance, the waterproof membrane has many other excellent features:
1. Withstand the external wind attack.
2. Keep good flexibility in low temperature
3. Light weight
5. Prevent air leakage
6. Water vapor permeability.
Although wind resistance and energy efficiency are the main properties of waterproof membranes, in recent years, the water resistance performance of waterproof membranes has also received extensive attention. In the new International Residential Code(ICC) of 2006, all houses are required to add waterproof membranes.The addition of this regulation prevent a large amount of moisture damage to the house, so that the attention of waterproof membrane has immediately changed from windproof to moisture proof.Because the waterproof membrane naturally has high waterproof performance, the requirements for the windproof performance is gradually increased.
What kind of installation can improve the wind resistance performance of the air barrier?
The wind-proof performance of different membranes are not the same. But the research shows that good wind-proof performance is not only related to the performance of the membrane itself, but also has a great relationship with the installation method of the air barrier.After years of research and field investigation, a very good installation method was found by our company.
1. The air barrier is still installed from the bottom up, and the lap is still 6-10 inches.The laps still need to be sealed with flashing tape.
2. Next, the important part comes.Double-sided butyl adhesive tape is used between the laps of the membrane. Wooden strips are installed above the air barrier at the position of double-sided butyl tape.The wooden strips are fixed to the sheath wall board by insulation screw.The cladding is installed on the wood strip then.This installation method can significantly improve the wind resistance performance of the air barrier.And the air layer formed by the wood strip can form a natural air insulation layer which also has some R value. The moisture collected by the air barrier can be easily dried up here, and more energy can be saved by this method. Meanwhile, people will have a indoor environment with higher comfort level.
3. At the top of the wall board, the roof membrane should cover the wall membrane will some laps. At the bottom of the wall board, a flashing system should be installed to guide the water collected by the air barrier directly to the ground but not to the bottom of the house.
Investigation report on the function of breathable membrane:
Reducing air leakage has been identified as one of the main ways to reduce energy consumption of buildings."Reducing air penetration can save 30 percent or more energy on home heating and cooling costs," says the U.S. Department of Energy.At the same time, the installation of the breathable membrane can reduce the invasion to the house such as humidity, noise, dust, pollutants and insects etc.
Some questions and answers about building wrap:
1. Will the installation of building wrap to the house be too airtight and not breathable?
A: A Building Wrap is a wind-proof and waterproof material, but that doesn't mean it's completely sealed.The building wrap also has another good performance, that is breathable performance.High quality building wrap usually has very good air permeability.While protecting the house from the wind and rain, it can also effectively discharge the moisture inside the house structure to the outside,making the house always keep dry and breathable.So that people living in the house can always have fresh air.
2. Is the building wrap durable?
Answer: the building wrap that installs correctly is fixed smoothly to the sheath wall. After the installation of building wrap, the cladding board should be installed as soon as possible. .If the cladding is not installed on time, some external dust and small scratches may affect the service life of the building wrap. But after the installation of cladding, there is no need to worry about this problem.
3. Is the building really waterproof and breathable?
A: Of course, the domestic regular inspection agencies have modelled on the international standard and set up a series of building wrap testing standards. The buyer can judge the building wrap easily through the test report by national inspection agencies.The following simple experiment can see the performance of building wrap directly.
4. How to judge the quality of building wrap?
Answer: domestic building wraps basically divides into two kinds.Both types of wraps are composed of three-layer, and there is no apparent difference.But they're actually compounded in different ways.The high quality building wrap is made by a hot pressing composite process, which can be applied to roofs with higher temperatures and keep breathable performance intact.The lower quality building wrap is compounded by glue adhesive and has lower breathable performance.However, when the temperature of the roof is more than 45 degrees Celsius, the permeability of the product will gradually be affected until the disappearance.A preliminary judgment can be made by touching the building wrap. The hot-pressed composite building wrap was compounded by hot pressure, so the product does not feel sticky when pressed.And the product compounded by glue adhesive does not have hot press compound point.