It is widely known that standing water or water leaks can cause serious damage to property. However, what many people don't realize is that water vapor can have the same effect. An insulating vapor barrier helps protect the insulation and the attic from water damage. The paper coating on existing insulation contains an impermeable asphalt layer that prevents water vapor from passing through it.
Fiberglass blocks, the most common insulation found in homes in the United States, have a predictable R value if they are not compressed, but it is difficult to place them around obstacles without leaving gaps. In most climates, a vapor barrier is necessary. Some builders use blocks coated with kraft paper to do this work, but experts recommend using uncoated blocks, covered in plastic and with all seams sealed. If the old insulation is damp due to the absence of a vapor retarder, it is best to replace the insulation when installing a barrier. If you add more insulation to what already exists, make sure to use uncoated blocks that do not have a paper support, or to place another insulating layer in the attic, on top of the existing insulation.
It was not until non-porous attic insulators were introduced that manufacturers began to include vapor barriers.
You should only install a vapor barrier in the attic insulation if you live in a climate with more than 8,000 heating degrees per day.A vapor retarder prevents water vapor from being deposited on the attic insulation and will circulate it across the roof. The correct way to install one is to first remove the existing insulation and then install a vapor retarder. Once you have decided to invest in a vapor barrier for your home, the key to achieving maximum efficiency lies in using the right insulation materials and following the correct installation techniques. However, if you live in a cold climate with moderate summers, attic insulation will benefit from a retarder. If you don't have a vapor barrier, the attic will become more humid during the winter and the insulation may become damp.
In those climates, a vapor barrier can prevent moisture from accumulating in the attic without compromising the home's insulation system. Tests show that a radiant barrier in an insulated attic can reduce the temperature of the attic by up to 30 degrees. Installing an insulating vapor barrier in the attic can help protect the structural integrity of your home, your air conditioning system, and your family's health. You'll need to install a vapor barrier before insulating the attic if the roof is porous at different points due to lighting installations or other accessories.
