It is a known fact that moisture in the air can trigger certain disorders and aggravate particular medical conditions such as hay fever asthma etc.
Attic insulation vapour barrier.
The insulation fiberglass or cellulose is then placed on top of the drywall with no vapor barrier above or below.
This acts as a barrier to keep heated moist air from rising up into the attic during cold weather.
In any case the vapor barrier must point to the warm side.
Adding a second vapor barrier could cause condensation to become trapped in the insulation between the two vapor barriers.
A vapor barrier basically helps to prevent moisture from entering your home through the ceiling floor or the walls.
Attic insulation should always be installed with the paper backing facing toward the living space the ceiling in this case.
The best approach for a vented attic in a cold climate is installing a layer of drywall with a good coat of latex paint the paint creates a semi permeable vapor barrier.
Most forms of attic insulation benefit from the addition of a vapor barrier to protect them from the harmful effects of moisture which can reduce their effectiveness over time.
This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses.
However all attics vented or unvented and in all climates should have an air barrier such as an airtight drywall ceiling.