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Water vapor can also be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Water vapor, which reacts to temperature changes, is referred to as a 'feedback', because it amplifies the effect of forces that initially cause the warming. Therefore, it is a greenhouse gas. [2]
The dampness results in vaporization where water vapor is transmitted into the building's interiors. Water vapor may enter the building through supply air ducts in building slabs and circulated by warm forced air. Water vapor can also enter a building through leaky return air ducts in homes with crawlspaces. [4]: 185–187
Waterproof is defined by the ASTM as a treatment that resists the passage of water under pressure. [1] Generally, damp proofing keeps exterior moisture from entering a building; vapor barriers, a separate category, keep interior moisture from getting into walls.
He consults regularly on building code and industry standards. [1] Widely known for his "Perfect Wall" concept, Lstiburek identified four key control layers within the building envelope (bulk water, air, thermal and vapor) critical to a building's behavior, long-term performance, and viability. He is a proponent of understanding the concepts ...
Open-cell foam is porous, allowing water vapor and liquid water to penetrate the insulation. Closed-cell foam is non-porous, and not moisture-penetrable, thereby effectively forming a semi-permeable vapor barrier. (N.B., vapor barriers are usually required by the Building Codes, regardless of the type of insulation used.
A vapor barrier is not typically intended to retard the migration of air. This is the function of air barriers. [8] Air is mixed with water vapor. When air moves from location to location due to an air pressure difference, the vapor moves with it. This is a type of migration of water vapor.
In construction, a building or structure is waterproofed with the use of membranes and coatings to protect contents and structural integrity. The waterproofing of the building envelope in construction specifications is listed under 07 - Thermal and Moisture Protection within MasterFormat 2004, by the Construction Specifications Institute, and includes roofing and waterproofing materials.
Water vapor, the gaseous state of water, is generally invisible to the human eye. [2] Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends on the temperature and pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air.