Advice that could save you thousands? DONT SKIMP ON THE RIGHT INSULLATION! This could actually lessen the years of your roof! I just put on a new roof. They have a new type of roof that is more efficient and vents from the top. But this meant I needed new insullation.....a certain type to go with the roof. My roofer and best friend said it becomes not a matter of cold or hot but that if I do not use the right insullation for my type of roof that my roof will only last 3 - 5 years. I speant $8,000 on my roof (it was so bad the wood even had to be replaced) and that was through a friend! Others quoted me $15-$20,000! It would not be worth it to go cheap on it. If you need 38 USE 38. It will save you money in the long run.