Vapor Permeable Roof Underlayment

Roof underlayment test compliance.

Vapor permeable roof underlayment.

They are also generally more expensive. Promotes long term drying of roofing assembly through vapor diffusion. Any material with a perm rating of 10 or greater is highly permeable. When all of your old shingles are removed the underlayment is rolled on to protect the exposed roof from elements until the new shingles can be applied.

The second period is after the new shingles have been applied. Or just stick with asphalt felt underlayment if you want a vapor permeable product. Is managed across these two different underlayment systems. Typically 15 felt for asphalt shingles and 30 for wood roofing were the common practice.

Underlayment works in two waves. A highly vapor permeable roofing underlayment air barrier ab material. Synthetics are manufactured with a vapor permeance that can be as high or higher than asphalt felt underlayment. The first period is critical.

Used on steep slope roofs of 2 12 9 46 degrees or greater pitch. According to the manufacturer the roofing underlayment features the patent pending vapor permeable polymer composite technology vppct developed by vaproshield. Follow up simulations showed if time aged roof shingles deteriorated and water penetration occurred onto the underlayment substantially higher moisture accumulation in the osb occurred for the vapor permeable underlayment. The underlayment continues to act as another layer of protection.