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                                               Ice Dams

A common sight this winter

So, what is an ice dam, and why should I be worried about them?

Snow on a roof can melt, flow down the roof until it comes to a colder roof section, and re-freeze.  When there’s a lot of snow, this ice can build up until it can actually trap water on the uphill side – it’s a dam made out of ice. Typical roofs are designed to shed water, not hold it, and dammed-up water can migrate in under the shingles and find a pathway into the house. That can wet the insulation, which not only reduces its effectiveness but can lead to mold growth. By the time it gets bad enough to actually start running down the interior walls, there’s a fair amount of damage already done.

How can I tell if I have a problem before it gets that bad?

A good early warning is icicles hanging from your eaves.  This indicates that water is melting off your roof, then re-freezing – and if it’s forming icicles, it’s probably cold enough outside that it’s forming ice dams. If you see a visible line of ice along your eaves, that’s the bottom edge of an ice dam.

 What should I do to prevent ice dams?

Well, that’s a good question, but the answer will depend on your specific situation – whether you even have ice dams, what your ice dams are due to, what your abilities are to fix it yourself, and what your trade-offs are if you have to hire someone else to get involved..  Let’s look at some solutions, starting with the simplest situations. If there is snow piled up on your roof, but no evidence of melting, you probably don’t have an ice problem. You might want to get the snow off any flatter sections of roof, because if it rains, that snow can get very heavy, but you don’t have an imminent leaking problem.  If you have ice buildup, the first step is to try and reduce the buildup on the roof, and figure out why it’s happening, which is usually due to conditions under the roof, in the attic space.

So I shovel off the roof, or use a snow rake?

Yes, and don’t try to remove the ice dams themselves – no hatchets, ice picks, etc., since you risk damaging your roof and making the problem significantly worse. And don’t just shovel off where the ice dams are, shovel off the whole roof. That’s because the snow is melting up higher on the roof and running down, so you want to limit how much there is up above the ice dam area so it doesn’t just keep coming down and re-freezing. But once that’s done, take some time and look at why that water is melting on your roof in the first place.

 How do I do that?  What do I look for?

If you have an attic, go up in it – if there is insulation on the floor of the attic space, then your attic should be just as cold as the outside air. If you’re having ice dam issues, it’s probably not; heat from the house is escaping into the attic and making the underside of the roof sheathing warm enough to melt the snow above.  There are three primary reasons your roof sheathing can get too warm:  air from inside your house escaping into your attic, insufficient insulation in your attic, and, if you have either of the first two, insufficient ventilation in your attic to carry away the heat.

 Should I just add more insulation up there? More insulation is better, right?

More is better, but insulation won’t block air leaks – if you have warm air coming into your attic through holes drilled for electrical wires or plumbing vent stacks, or through recessed light fixtures or from bath vent fans, those are going to be the biggest sources of heat, not to mention the biggest factor in your heating bill.  The money you save in heating costs, by fixing air-leakage issues, could pay for more insulation! So before you add insulation, go around and stop up any air leaks! Also, be careful when adding insulation that you don’t block the ventilation system, for example the soffit vents if your home has them.

Okay, but this is starting to get complicated – what if I don’t feel comfortable doing all this investigating and sealing, not to mention the shoveling?

Call in a professional to help – but make sure they are reputable, insured, and knowledgeable. Contractors who are members of trade associations, such as the Home Builders and Remodelers Association of New Hampshire, or are accredited by the Better Business Bureau have been vetted by these organizations and are committed to fair and honest practices. Ask for references, check them out, pick somebody you feel comfortable with and who can explain the situation and their recommendations in a way that makes sense to you.  There are successive levels of fixes for ice dams, ranging from band-aid approaches that put off the problem until warmer weather to immediate home surgery, and a good contractor can provide a solution that meets your needs, timing and budget.

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