over this winter and the past ones, ive noticed that i get alot of ice build up on my roof. i was doing a little research and it seams that without proper insulation, heat escapes thur the roof and melts the snow on the roof and it turns into ice. i went into the attic and crawl spaces and i see there is no insulation on the roofs underside, there is insulation on the walls and floor. ive also heard that you are not to insulate the underside of your roof because it needs to breath so my question is, should i replace the old insulation with something better or put some on the underside of the roof. im getting new shingles the year and i want them to last 30 years.