If the inside of your garment feels damp, a leak could be the problem, or it could be time to renew the durable water repellent (DWR) finish. As the DWR starts to wear off through abrasion, dirt and general usage, the garment can wet out, particularly in the shoulder and upper back areas. Even though the garment remains waterproof, external moisture can create a feeling of dampness and cause heat loss. (See this article on renewing the water repellency.) If the moisture is due to leakage through the membrane, it's covered under the warranty.