Dam All This Ice! Preventing Ice Dams Before They Start
Icicles hanging from power lines, trees and other people’s homes can be absolutely gorgeous, but when those delicate frozen water daggers are hanging from yours, it may make your stomach do a barrel roll. Why? Well, it’s just one of many signs that your home is at risk for ice dams.
What’s an Ice Dam, Anyway?
An ice dam occurs when there’s a disparity in the temperature of your roof that causes snow and ice to melt off of the main portion of the deck, then refreeze at the eaves. This results in a sort of hump that slows or prevents further run-off of that same type of melt — it’s a dam literally created out of ice. It may cover the edge of your roof or spill over into your gutters, but either way it’s not good news. You might also notice icicles forming, this is a sign you absolutely need to get in gear and figure out what’s going on upstairs.
Ice dams are no good for several reasons, including the potential to damage your gutter and roofing materials or divert water into your attic or inside the exterior wall. They’re spendy problems that can have you standing on the ground in the snow shouting and shaking a fist at the sky. It’s much better to prevent them now than to have to deal with them later.
The Mechanics of an Ice Dam
Ice dams are the result of attics that are improperly sealed or insulated. There, I said it. It’s probably not your fault, your house may be really old or maybe you have an addition that wasn’t quite ventilated properly. Let me explain how they work, then we’ll get to how to make them stop.
When it snows, it’s actually good if that snow accumulates on your roof. That means that your living space, the part that you’re heating, is tightly sealed and there’s not heat leaking into the attic. A warm roof is never consistently warm, it’s only warm from the peak (remember, heat rises) to some point below, but never to the eaves (the most narrow bit of the roofline). The eaves are just as cold as it is outside, no matter how much heat you pump into the attic — that’s where the problem lies.
So the ultimate end goal is to keep the attic as cool as you can in the winter, as well as the summer.
Getting Started with a Permanent Fix
We’ll hit on temp fixes for ice dams later, but first I want to go over how to actually fix this problem for good. It will be better for your house, your roof and your wallet if you cure the ill rather than bandaging it year after year. Below, you’ll find a checklist of things you can do to cool that attic off!
Seal all cracks, gaps or holes between the living space and attic. These can be hard to see if you have a lot of insulation, but if you’re having ice dam problems, the chances are good that you don’t. Go around the attic slowly looking for any points of light coming from your living space. Fill these with caulk or expanding foam, depending on the size of the hole and the location.
Exhaust everything to the outside. Does your bathroom fan exhaust into the attic? How about your dryer vent? Make sure all your exhaust ducts are venting to the outside of the house, not just to the attic. Those bursts of warm air are not your attic’s friends.
Check your HVAC ducts. If your HVAC system lives in your attic, it could be the main source of heat leakage. Check all the ductwork, starting at the unit and moving outward. Tape or screw together any ducts that are loose or have fallen apart. While you’re at it, make sure the vents are securely attached at the duct endpoints.
Add insulation. Check your insulation level. You probably need more, but go ahead and get a ruler to determine exactly what’s going on. If your insulation isn’t even coming up past the ceiling joists, you definitely need another blanket to help keep that warm air where it belongs. Don’t forget to insulate sealed can lights, attic hatches and cover your whole-house fan as well.
Ventilate the roof. You can’t prevent all heat from accumulating in your attic. Even with your best effort, the sun’s going to contribute something. That’s why adding soffit and roof vents is a good bet. Both types of vents should be sized so that there’s at least one square foot of opening for every 300 feet of attic floor. You want the intake and output to be roughly the same to create optimal flow. The soffit vent will pull cool air in from outside and the roof vent will push out hot air from the peak of your attic.
Flash your chimney. This isn’t Mardi Gras and you’re not getting any beads, but flashing your chimney is another way to seal away heat. Never use spray foam or similar products to seal gaps around chimneys unless you really want to experience a house fire. Instead, choose fire-safe L-shaped chimney flashing.
Short Term Fixes
I understand that you’re not ready to get into the attic and do all it takes to get it ready for winter. You’re busy, life is happening. You’re not the only one. There’s really only one great short-term fix for ice dams: heated cables.
You install these with clips along your roof’s edge (much like with Christmas lights) in a zigzag pattern so the entire eave has coverage. They plug in from the ground, so you can unplug them on nice days and save money on electricity. Heated cables are not a long term solution, however, and they’re costly in the long run. Go ahead and make plans to get your attic into ship-shape come springtime.
Safety First When Dealing with Ice Dams
There are a lot of things you shouldn’t do when dealing with ice dams. Don’t bang on your roof, don’t scrape your roof, don’t stab your roof, don’t do anything to your roof that involves violence or corrosive substances. These favorite DIY ice dam fixes end up damaging roofing, so you not only have an ice dam, you now have a roof to fix. You’re just compounding your issue. Be nice to your roof. Also be nice to yourself — all that banging around on a slippery ladder in the cold could easily result in a fall.