Does Roxul Need A Vapor Barrier In Attic

Sup 2 sup and the need to install a separate vapor barrier.

Does roxul need a vapor barrier in attic.

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. After the insulation is in place you will want to add a vapor retarder sometimes called a vapor barrier if you need one. 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 doing a complete renovation of my house right now and i ve chosen to insulate with roxul comfort batts.

In this moisture prone space you don t want water vapor from the ground drying to the inside of your home. No you don t need a vapor retarder class i or otherwise. Seal the air leakage pathways. I am in zone 4 right on the edge of zone 5 in long island ny.

It is important to note that air control is more important than vapor control. 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. Youll see that i mention roxul a lot in that tutorial but roxul is exactly the same as rockwool. A vapor retarder is a material used to prevent water vapor from diffusing into the wall ceiling or floor during the cold winter.

Not every wall does. Moisture transport by air is significantly higher 100x than moisture transport by diffusion. Whether or not you need a vapor retarder hinges on three main factors. This is primarily due to the kerdi board or wedi.

Roxul would be my choice for a batt insulation. In some cases the vapor barrier also acts as the primary material in the air barrier system. 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. 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.

The downsides are the higher cost per ft. A plastic vapor barrier is best installed in a vented attic within climates with over 8 000 heating degree days.