Air leaks around my old Marvin Casemaster Windows - will new seals help?

ANSWER: Most Definitely - but all air infiltration may not be that simple to deal with.  Often times other issues are the root of the problem - bad or broken glazing bead, the wrong weather strip or seals with a built in memory or other seal issues - this is especially true in windows and doors that are more than 7-10 years old. Removing and replacing your old seals and weatherstrip may be all you need to do... and it's a simple homeowner weekend project.