Flat roofs are not ideal - they have a lot of issues with standing water from easily clogged gutters. Ponding water that remains on the roof will eventually find a way in to the substructure. This can easily lead to extensive water damage. Flat roofs require regular maintenance and need to be kept clear of debris as much as possible.
It's the middle of the heating season - how well is your furnace "breathing" through the filter? Have you been changing the filter regularly? If not, January is a great month to start a regular maintenance cycle. Furnace filters should be changed every 3 months for optimal performance of the furnace. A clean filter allows better air flow and a furnace that doesn't have to work as hard to meet the heating demands of your house.
Check out these other posts from Jovag Home Inspection for further information on furnace systems and maintenance.
Brian Jovag, owner of Jovag Home Inspection.