Ceiling Vapor Barrier: Yes or No?
During the energy crisis of the 1970s, it was thought that tightly sealed walls and ceilings with a vapor barrier was essential to blocking heat transference and reducing energy costs.It was determined that unless the seal was absolute, there could be serious structural problems and allergic reactions to mold in sealed walls.It is still good practice to minimize heat loss through walls, ceilings, and floors, but it is also important for the vapor barriers to be installed correctly and that walls can breathe.
There is still debate over how necessary vapor barriers are.Vapor barriers are important under certain conditions, but not necessarily as a whole-house solution for every home.Water vapor can get trapped inside a home or office if the conditions are different than outdoors, and a well-installed Vapor Barrier is recommended.Vapor barriers are important for rooms with high humidity.
Studies show that 98 percent of the water transfer through walls occurs through air gaps, including cracks around electrical outlets and baseboards.Installation of vapor barriers on wall surfaces must be done in conjunction with the sealing of air flow-gaps in walls and ceilings.
A poor effort at establishing a vapor barrier may be worse than nothing at all.Vapor barrier strategies are meant to stop the collection and corrupting of building materials.A wall that is more porous can breathe better and be less susceptible to long-term moisture problems if it is properly installed.This condition is problematic where vapor barriers are installed on inside as well as outside wall surfaces, as such a wall cannot breathe at all.
Vapor barriers are now only recommended for certain conditions and methods for creating them must be tailored to fit the climate, region, and type of wall construction.In a humid southern climate built with brick, the recommended vapor barrier is vastly different than in a cold northern climate with wood siding.Refer to current local code recommendations when deciding if and how to install vapor barriers.The outer wall construction already has a material with vapor barrier properties.
The following practices should be kept in mind if vapor barriers are recommended by local building practices.