Add another housewrap to the category. This one, Hydrofilament drainable housewrap, provides a 1-millimeter gap that enhances drainage behind siding up to 140 times more than standard products. Sold in 39-inch-by-100-foot rolls, it prevents moisture and air penetration into the building but allows moisture vapor to exit. Cost: 13 cents to 17 cents per square foot. Benjamin Obdyke. 800-346-7655.