What is a good perm rating?
What is a good perm rating?
A perm rating of less than 0.1 is considered a Class I impermeable vapor retarder (which is also considered a vapor barrier); perm rating between 0.1 and 1 is considered a Class II semi-permeable vapor retarder; a perm rating between 1 and 10 is a Class III permeable vapor retarder; and a perm rating greater than 10 is …
What is the perm rating of 10 mil poly?
Product Data Sheet
| Properties | PERMINATOR (10 Mil) | PERMINATOR (15 Mil) |
|---|---|---|
| Water Vapor Permeance ASTM E-96 Perms | 0.0183 | 0.0063 |
| Puncture Resistance ASTM D 1709 Method B Grams | >3500 | >3200 |
| Tensile Strength ASTM E 154 Section 9 Lb. Force/Inch (kN/m) | 52 (9.12) | 72 (12.61) |
What is a Class 1 or 2 vapor retarder?
Class I – Very low permeability vapor retarders – rated at 0.1 perms or less. Sheet polyethylene (visqueen) or unperforated aluminum foil (FSK) are Class I vapor retarders. Class II – Low permeability vapor retarders – rated greater than 0.1 perms and less than or equal to 1.0 perms.
Is a higher perm rating better?
A perm rating is the unit telling us the mass rate of water vapor flowing through one square foot of material. A metric perm is defined as 1 gram of water vapor per day, per square meter, per millimeter of mercury. In both cases, the higher the perm rating, the more water vapor can travel through a material.
What is a good perm rating for vapor barrier?
Vapor impermeable: 0.1 perms or less. Vapor semi-impermeable: 1.0 perms or less and greater than 0.1 perm. Vapor semi-permeable: 10 perms or less and greater than 1.0 perm.
Is 6 mil plastic sheeting waterproof?
Polyethylene sheet and film are used for many different construction and DIY projects. Some common applications for this product include using it as a vapor barrier for concrete or between drywall and insulation. They also can be used to cover a crawl space or under wood floors. Plastic sheeting is waterproof.
Which is thicker 4 mil or 6 mil?
This thickness is indicated as MIL (thousandth of an inch). 1 MIL is a measurement unit that equals 0.001 inch which is about the width of an average human hair. Generally speaking, higher MIL designation equates to a thicker and strong plastic sheathing….Understanding Thickness of Plastic Sheeting.
| Rating | Thickness |
|---|---|
| 6 MIL | 0.006 inch |
| 9 MIL | 0.009 inch |
What perm rating is a vapor barrier?
0.1 perm
So, according to the Building Science Corporation, “A vapor barrier is defined as a layer with a permeance rating of 0.1 perm or less.”
When should you not use a vapor barrier?
You may find that vapour barriers are often not required in warmer climates. And, if installed in the wrong climate or on the wrong side of building materials, a vapour barrier can cause more harm than good. This circumstance may prevent water vapour from drying, which in turn can cause rot and mold.
What is the Perm rating of polyethylene?
The most widely used vapor barrier is 6 mil polyethylene, which has a perm rating of 0.06. Given the combina- tion of high RH indoors, and very cold weather outside, measurable amounts of water vapor will pass through 6 mil polyethylene.
Can a 6 mil polyethylene be considered a vapor retarder?
Even 6-mil polyethylene, one of the most common vapor barrier materials, has a 0.06 perm rating and can therefore be considered a vapor retarder in spite of its extremely low permeance. The most recent edition of the International Residential Code (IRC) splits vapor retarders into the following categories, regarding their permeance:
What is the mils of polyethylene sheeting?
Mils: Polyethylene sheeting is measured in ‘mils.’ A mil is equal to 0.001 inch of thickness. Codes for residential applications often cite a 6 mil (0.006-inch thick) minimum reinforced poly vapor barrier. However, Americover recommends 10 mil or higher, for crawl space applications.
What’s the difference between Perm and vapor retarder?
Some texts prefer the word retarder to barrier because barrier implies 100% blockage of water molecules or moisture. While few materials provide a 100% barrier to moisture movement (glass would be an example), a number of materials have such low perm ratings as to serve effectively as a moisture barrier. Class I vapor retarder: 0.1 perm or less.
