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Roofing Glossary
Choose from ABC's at top of page for more terms |
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| Vapor Migration |
the movement of
water vapor from a region of high vapor pressure
to a region of lower vapor pressure.
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| Vapor pressure Gradient |
a graph, analogous to a temperature
gradient, indicating the changes in water vapor pressure
at various cross sectional planes through a roof or
wall system. |
| Vapor Retarder |
a material designed to restrict
the passage of water vapor through a wall or roof.
In the roofing industry, a vapor retarder should have
a perm rating of 0.5 or less. |
| Vent |
an opening designed to convey
water vapor or other gas from inside a building or
a building component to the
atmosphere, thereby relieving vapor pressure. |
| Vermiculite |
an aggregate used in lightweight
insulation concrete, formed by the heating and consequent
expansion of a micaceous mineral. |
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