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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 ...
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
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.
Permeability can be reported in perms, a measure of the rate of transfer of water vapor through a material (1.0 US perm = 1.0 grain/square-foot·hour·inch of mercury ≈ 57 SI perm = 57 ng/s·m 2 ·Pa). American building codes started classifying vapor retarders in the 2007 IRC supplement.
Water vapor is lighter or less dense than dry air. [11] [12] At equivalent temperatures it is buoyant with respect to dry air, whereby the density of dry air at standard temperature and pressure (273.15 K, 101.325 kPa) is 1.27 g/L and water vapor at standard temperature has a vapor pressure of 0.6 kPa and the much lower density of 0.0048 g/L.
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.
Ventilation in a structure is also needed for removing water vapor produced by respiration, burning, and cooking, and for removing odors. If water vapor is permitted to accumulate, it may damage the structure, insulation, or finishes. [citation needed] When operating, an air conditioner usually removes excess moisture from the air.
Housewrap (or house wrap), also known by the genericized trademark homewrap (or home wrap), generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a weather-resistant barrier, preventing rain or other forms of moisture from getting into the wall assembly while allowing water vapor to pass