Durability

Insulating sheathings are generally fairly durable materials, however, they are not completely resistant to degradation. Polystyrene boards will degrade if left exposed to UV radiation for prolonged periods of time. The boards will discolor and a thin dusty film will form on the boards. Faced Polyisocyanurate is more resistant to UV degradation, however the unfaced polyisocyanurate boards are also susceptible to UV degradation.

EPS boards are less durable for excessive handling. The edges of the boards can break off as the bond between the expanded beads is not as strong as the matrix formed with XPS and polyisocyanurate. This can leave the boards with more rounded edges and decrease the thermal value at the joints between the boards. Careful cutting and handling is recommended when using EPS boards.

Most insulating sheathing boards are resistant to moisture, however problems with warping and cupping of the foil faced polyisocyanurate have occurred in the past when the boards have been left exposed to the weather for extended periods of time.

As a general rule, it is considered good practice to store the boards in a protected, covered, and dry location on site and to limit the amount of time the boards are left exposed before being covered over by the cladding material.