In short, it sounds like the source of your problem from warm air leaking into a cold space. By 'allowing' the attic temp. to equalize with the outside temp., you eliminate problems related to DIFFERENCES in temps..
Heating the attice is a waste of good $$$. If you WANT to do this, then consider 'finishing off' the attic space into something liveable. THis way, you can use the space and not get the feeling you're throwning your $$$ away. Yes, you need to find the source of the heat-escaping into the attic.
One way to get a good reference or 2 is to talk to your builder or your Home Inspector for pros that 'work' in this field. They're both good sources for leads. My best to ya and hope this helps.