Does Roxul Need A Vapor Barrier In Attic

Vapor barriers installed on the interior side of assemblies impede them from drying toward the interior this is a problem for air conditioned spaces and can be an issue when there is also a vapor impermeable material installed on the assembly s exterior creating a double vapor barrier wall assembly.

Does roxul need a vapor barrier in attic.

Not every wall does. I ve read that i need to use a vapor barrier but i ve also read that vapor barriers can cause houses to be moldy or can cause rot inside the walls because the walls cannot dry out properly. Seal the air leakage pathways. It is important to note that air control is more important than vapor control.

I am in zone 4 right on the edge of zone 5 in long island ny. By the time you paint the drywall though you ve brought it into the class iii vapor retarder range between 1 and 10 perms and even less water vapor will diffuse through. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. This is primarily due to the kerdi board or wedi.

A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days. I am doing a complete renovation of my house right now and i ve chosen to insulate with roxul comfort batts. Roxul would be my choice for a batt insulation. And by the way if you re remodeling a shower and use rockwool with kerdi board or wedi s shower system there s no need for a vapor barrier.

A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. In some cases the vapor barrier also acts as the primary material in the air barrier system. The downsides are the higher cost per ft. Sup 2 sup and the need to install a separate vapor barrier.

No you don t need a vapor retarder class i or otherwise. For a chart of vapor retarders by climate zone see the naima s insulation and vapor retarders in crawl spaces install a class i vapor barrier such as a vinyl liner on walls and floor. Provide greater r value per inch which can be important if you need to add r 19 in a 2 x 4 framed wall for example. Youll see that i mention roxul a lot in that tutorial but roxul is exactly the same as rockwool.

Whether or not you need a vapor retarder hinges on three main factors. The vapor barrier does not need to be sealed to function adequately.