Ice dams happen when heat (which travels upwards) moves from the house, through the attic, and melts snow on the roof. The melted snow (now water) runs down the slopes of the roof, until it gets to the edge (the part of the roof that does not have house underneath it), where it is colder and then freezes again. You get a big build-up of ice as this happens again and again, and this is called an “ice dam.” You’ll also get a bunch of icicles (which can start to pull down your gutters, and put undue weight and stress on the edges of your roof. The ice can also back up under shingles, and start to melt into the house, causing damage to plaster/sheetrock, rotting walls, peeling paint, wet insulation, a whole host of problems.
I’ll admit that I was not as proactive of a landlord when I first bought the duplex as I am now, and while I knew that sealing and insulating the attic needed to be high on my to-do list, I didn’t get to it that first fall. I figured that one bad winter couldn’t hurt the new roof THAAAAT much, right? Well, as the winter settled in, and we got more and more snow, I became obsessed with monitoring the state of my roof, and comparing it to others in the neighborhood. When it snowed heavily, there was a blanket of snow on most of the neighboring houses, but mine was practically snow-free on the upper parts of the peak, with more and more snow appearing as you went down the roof. After a few days of partial melting in the snow, the icicles started to appear. One area was particularly bad — a three season porch (which the tenants used year round) was not covered by the attic at all, and started getting gigantic icicles hanging down in one corner — I believe they were 12 feet long at one point — and definitely the giants of the neighborhood.
SURVEYING THE DAMAGE
I consider myself lucky. The icicles were large enough (and heavy enough) that they partly pulled down the gutters — however, it was only about $350 to get them repaired in the spring. Luckily that was the extent of the damage — no water came inside the house, no damage to walls, plaster, ceilings, or the like. And (thankfully) no one happened to be walking under any icicles at inopportune times.
WHY THE (RELATIVE) LACK OF DAMAGE?
Well, I’m only guessing here, but I think that what saved me was the fact that my attic wasn’t poorly or inadequately insulated — it wasn’t insulated. At all. I had enough heat traveling up through the attic that most of the snow melted at a temperature warm enough to make it off of the roof before freezing.
THE OTHER REPERCUSSION OF NO INSULATION
My upstairs tenants’ heating bill was through the roof, literally. (in fact, I wonder if that’s where that terminology came from? their heat was going through the roof??) There had also been problems with their furnace at the beginning of the winter. The limit control was broken, and keeping their fan blowing air long after the furnace had stopped emitting heat, causing their apartment to be cold and drafty, which caused the heat to kick in again, in an endless cycle. Luckily, I had signed up for the appliance repair plan through my local gas company ($36/month to cover all of the appliances in both units), so I got about $200 of repairs on the furnace for no additional expense. Their gas bill started edging down after this repair, but was still ridiculously high (and I knew why, although I wasn’t about to tell them “there is NO insulation upstairs – you live in a house that has been neglected for the past 50 years”) But I started the insulation process shortly after the first of the year — I felt responsible, and didn’t want to be a slumlord, after all. And it did certainly need to be done, sooner rather than later.