14-15 isn't old for a cat... a lot of cats live to be in their 20's.
How is his diet? sometimes problems in an animals diet can be manifested in their fur/skin. Dry flaky skin along with a dull coat could be a sign that there is something lacking in his diet. I would call the vet and discuss what you are feeding him and see if that could be what is causing it.
It is also possible that it is ringworm or even mange, he should be seen by a vet to rule those out. Is he an indoor only, an in/out cat or an outdoor only cat?