Moisture And The Warm Attic

By Author: Bob
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Moisture and Condensation


The trends of the modern energy conservation in residential construction, especially older homes, have presented the roofing industry with challenges. Homes are commonly retrofitted with new windows and insulation and sidings with house wrap-style vapor barriers. All of these measures are valid; however, the key element of moisture condensation is the most misunderstood concept among home renovators.



Warm Air is a Moisture Conduit
It is not the outside conditions such as the wind, but interior heat that is the conduit that carries with it most of the harmful moisture within residential dwellings. The sources of the most damaging moisture are not rain or snow or ice from the outside, but the very every day activities that produce water vapor within the home. This vapor is picked up and carried by warm air. Whatever the humidity level within a home during the winter, warm moisture laden air escapes the living area of the dwelling. Just as your breath immediately will fog the inside of your cold automobile's windshield in the winter, so will warm attic air ...
... carry moisture up to the back side of the cold roof deck and there, drop its moisture. The nails of the installed roofing system, transfer cold right into the attic space. Frost can often be seen inside the attic, especially forming on the nail shanks. The attic can then take on a terrarium effect and actual rain-like precipitation begins to fall onto the attic floor.

Moist Fiberglass Insulation
In most attics, fiberglass insulation is on the attic floor. When this insulation which relies on trapped air pockets to perform gets wet, it flattens out and looses its insulative properties. Mold often grows in moist, warm attics as mold spores are carried by air and can be found virtually anywhere. The overall heath of the inhabitants of the dwelling is at risk in serious cases. A comparison has been made before, that when a person takes a tee shirt prematurely out of the dryer and puts it on, it becomes readily apparent to that person that a rapid loss of body heat from the damp garment is occurring. That person gets a chill from having worn a slightly damp garment. This is similar to the condition of insulation that begins to get wet from falling condensation in the attic. Heat from the home is drawn into moist, cooler insulation, just like that damp tee shirt. The insulation barrier that is supposed to be an energy conservation asset and reflect heat has now become a liability, and the heating system is working harder and using more energy. The degree of moisture within the insulation that causes this effect cannot always be detected by feeling the fiberglass with the human hand.

Vapor Barriers
Millions of dollars are haphazardly spent on vapor barriers every year. The emphasis has been on the outside of the building during renovation work. This tightening of the shell of the building actually causes more problems for moisture condensation, especially in the attic. New underlayment techniques are providing barriers that when cold, cause warm, moisture laden air to drop its moisture.

Solutions
The solutions are simple to offer, but sometimes costly to implement. One, of course, is to properly ventilate your attic, ensuring all openings are working in a convective balance according the square footage of the home. This is easily done and it is a very important part of retrofitting a roofing system. It must be done properly, however, and not with a shotgun approach. Another solution is to properly insulate the attic so that the attic is cold and not warm in the winter. The best way to stop the water vapor from condensating is to install a vapor barrier on the warm side of the living area. This can be done when renovating the interior of the home.

We provide you with a written ventilation recommendation based upon government specifications. With this form and your new roof, you have added value and assurance that your roofing system will last the test of time.




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