The level of breathability is determined by how easily air can pass through the fabric. Fabrics that naturally breathe well are assigned a rating of 3 or better. The breathability of a fabric should always be considered before selecting a fabric for a specific application. If an air tight enclosure is made of fabric that does not breathe well (waterproof fabric), condensation and mildew will become a problem. Waterproof fabric is an excellent choice for bimini, awning, and dodger tops, but enclosed covers may require ventilation with screens or vents.
 

│ │ │ │ │ │ Sunbrella Furniture Fabric │ 5 │ 1 │ 4 │ 3 │ 5 │ 5 Sunbrella Marine Grade │ 4 │ 3 │ 2 │ 5 │ 5 │ 5 Sunbrella Plus │ 3 │ 4 │ 3 │ 5 │ 5 │ 4 Sunbrella Supreme │ 2 │ 4 │ 3 │ 5 │ 5 │ 4 SeaMark │ 1 │ 5 │ 4 │ 5 │ 5 │ 4 Surlast │ 4 │ 3 │ 5 │ 3 │ 5 │ 4 Top Gun │ 2 │ 4 │ 5 │ 3 │ 2 │ 3 Odyssey III │ 3 │ 3 │ 4 │ 3 │ 2 │ 3 Stamoid Vinyl │ 1 │ 5 │ 4 │ 4 │ 4 │ 3/5 Shelter-Rite Vinyl │ 1 │ 5 │ 5 │ 3 │ 4 │ 5 Cotton Duck (Marine-treated, preshrunk) │ 5 │ 4 │ 4 │ 1 │ N/A │ 4