Does Roxul Need A Vapor Barrier In Attic

Not every wall does.

Does roxul need a vapor barrier in attic.

Moisture transport by air is significantly higher 100x than moisture transport by diffusion. In some cases the vapor barrier also acts as the primary material in the air barrier system. In this moisture prone space you don t want water vapor from the ground drying to the inside of your home. 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.

I am in zone 4 right on the edge of zone 5 in long island ny. 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. It is important to note that air control is more important than vapor control. Seal the air leakage pathways.

After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. 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. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter. If your climate does not meet these conditions a vapor retarder like latex ceiling paint will work well for your house if you are in all other climates except the hot dry and hot humid.

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. The downsides are the higher cost per ft. 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. Whether or not you need a vapor retarder hinges on three main factors. Roxul would be my choice for a batt insulation. Sup 2 sup and the need to install a separate vapor barrier.

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. The vapor barrier does not need to be sealed to function adequately.