After the vapor

After the vapor barrier is in place and all openings lapped or taped (small tears may be repaired by taping over them with a quality duct tape), bricks, other small masonry pieces, or an equivalent material shall be used to prevent movement of the barrier. Other methods used to prevent movement of the barrier shall be submitted to TVA for approval on a case-by-case basis. Ground cover shall be used in conjunction with ventilation, not in place of it.  − In extremely damp underfloor areas where there is concern over the possibility of drying out the residence too rapidly, the vapor barrier should be installed initially to cover approximately 50 percent of the ground surface, with enough material folded back for eventual 80-percent coverage. • Vents—After determining the correct number of vents required for the particular underfloor area, vents shall be evenly distributed around the foundation to provide the best air flow over the greatest area. When only four vents are required or possible, two vents should be located on the prevailing wind side of the house and the other two on the opposite side. As with attic vents, foundation vents should remain open in winter as well as in summer to provide the necessary ventilation. However, during freezing conditions, it is advisable to temporarily close vents located next to water pipes in order to lessen the chances of water in the pipes freezing. − Vent openings shall be located as close to building corners as is practical and should provide cross-ventilation through at least two opposing foundation walls. Adequate cross-ventilation shall be provided whenever possible for all separate areas within a partitioned crawl space.  − Vent locations for proper cross-ventilation of crawl space areas shall be defined according to the “polygon method.” − First, the crawl space is sketched with the location of all existing and/or proposed vent openings shown. The vent opening locations are then connected with straight lines (which do not cross each other) to form a polygon (i.e., a multi-sided figure, such as a triangle, rectangle, pentagon, hexagon, etc.). If the crawl space is partitioned, a polygon is drawn for each separate crawl space area. − If the area of the resulting polygon covers 70 percent, or more, of the crawl space area to be ventilated, then the distribution of the ventilators is adequate.  − If the area of the resulting polygon does not cover 70 percent of the crawl space area, then additional vent openings or relocation of proposed vent openings shall be required to allow a similarly drawn polygon to indicate an adequate distribution of ventilators.  − All other possible steps (such as making access doors into screened vents, enlarging existing foundation vents by removing wooden screen frames, etc.) should be taken to increase total existing net free area instead of adding more openings in foundation walls