What Is Vapor Retarder In Insulation?
What Is Vapor Retarder In Insulation?
A vapor retarder or vapor barrier is a building material that slows down the transmission of water vapor between two zones with different moisture levels.
In other words, if you have an area where it’s humid and another area where it’s dry, then you may want to install some barrier between them so that moisture doesn’t pass from one place into another.
A vapor retarder is a building material that slows down the transmission of water vapor between two zones with different moisture levels.
It is commonly used in construction as an insulation layer but can also be used as a component in other applications such as weather-resistant coatings or paints.
A vapor retarder will not block all moisture from passing through it; instead, it acts like a barrier that slows down the movement of moisture molecules through the material until they reach equilibrium with their surroundings.
What Are Two Common Types Of Vapor Retarders?
There are two types of vapor retarders: class I and class II.
- Class I vapor retarders
Class I vapor retarders are very low permeability vapor retarders. These materials are used in areas with a high risk of condensation and moisture damage, such as basements and crawl spaces.
Class I vapor retarders can be installed behind sheetrock or other interior wall coverings to prevent moisture from entering your home through the walls.
They’re also used underneath floors, between floors and ceilings (in crawl spaces), or even on top of roofs to keep out rainwater that could otherwise seep into your house through cracks in the foundation or roofing materials.
- Class II vapor retarders
Class II vapor retarders are used in applications where a Class I vapor retarder would not be sufficient. For example, if you have an insulated and air-sealed attic that still feels cold, it might be worth installing a Class II vapor retarder on top of your existing insulation.
Class II vapor retarders are also used when water vapor is present but not in great quantities–for example, if your crawl space has high humidity levels due to being above grade and exposed directly to rain runoff or ground moisture (through cracks in concrete slabs).
Where The Vapor Retarder Should Be Installed?
It’s essential to place the vapor retarder on top of the roof deck, not between rafters or joists. This prevents condensation from forming in the wall by limiting how much moisture can get through the roof and into your home.
The optimal location for a vapor retarder is right below where insulation is installed. This allows heat from inside your home to pass through without being blocked by any additional layers of material (like drywall).
Suppose there are multiple layers of shingles or other materials on top of each other. In that case, it’s best practice for these materials to be installed before installing any insulation below them so that they’re protected from water damage caused by leaks or water buildup when installing new shingles later down the road.”
