You might think a roof is just a roof and that as long as it is constructed properly, that this should be enough. Different locales have considerably different weather patterns, and there is the range from excruciatingly hot to bitter cold. Considerations in these opposites make a difference in not only your own personal comfort, but your wallet, too, when it comes time to pay the utilities.  The biggest thing to remember is that a roof is a system, not just something on top of your house. Roofs require proper ventilation, insulation and water barriers. Without these three things in place, the best laid roof is destined to fail. This results in interior damage and costly repairs. Knowing the basics of a roof system is more than just picking the best shingle you can afford. Older homes especially suffer from improper installation. When a roof is replaced, it is time to fix those issues to insure your roof and home don't suffer from the effects of an improperly installed roof.