Last week we received more snow. It's probably reached a depth of about 2 feet in my yard. Nothing too exciting, except all of the snow piled up on the roof and the warm March sun have started to cause ice dam problems on many of the houses.
The ice dams are caused when warm air from the living area of the house escapes up into the unheated attic area. When the warm air starts to warm the underside of the roof, it causes the snow to start to melt....and then refreeze...melts.....you get the picture. As the water melts & refreezes, it can work its way under the shingles & roof sheathing and into the insulation and ultimately into the walls & ceiling of the house. The first clue are those pretty icicles that innocently start to form at the overhang.
I've worked really hard over the past 4 years in weather proofing my house. And have pretty much eliminated the ice from forming. But, I knew this spot was going to be a problem for me this year if it snowed. I've been removing aluminum from around the house. The front overhang had this funky metal drip edge that had been clipped every few inches, so they could "fit" it around the curve. There is a huge gap that I am sure is leaking warm air. Nothing I can do until I'm able to call a roofer to redo that whole section of roof in the Spring......except periodically knock down the icicles and remove some of the snow. The weather is pretty warm so it should melt pretty fast.
You actually can tell a lot about your roof after a big snow. If I walk around the block, I can see houses where the snow is almost entirely melted off of their roof. This means that a lot of hot air is escaping through their roof and they are significantly under insulated. They essentially are heating their house & about 6" above it. Icicles & ice dams point out specific spots where more insulation or expanding foam should be used to block bypasses. Small footprints, means you might have a raccoon living in your chimney ;-)
My roof will start to develop lines in the snow soon that show where insulation was put between the studs and where drywall was attached directly to the studs (to keep headroom). I have hot air escaping through those studs. The rest of my roof holds on to the snow pretty well, so I'm generally happy.