If Tyvek is exposed to sunlight for too long, it becomes less water-resistant. After more than 120 days, the UV-resistant property of Tyvek becomes weaker. Overexposure causes Tyvek to stain, lose tensile strength and eventually tear. However, if you need to use Tyvek longer, you should use something other than the normal Tyvek. Instead, use the Tyvek 1560K, which does not degrade in UV light.