Insulation and weatherization across Massachusetts and Rhode Island.Check your community
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Insulation and weatherization across Massachusetts and Rhode Island.Check your community
How to stop ice dams for good is an attic question, not a roof question. In 2015 an insurer covering 215,000 Massachusetts homes asked the state for permission to make homeowners absorb up to $10,000 of ice dam damage before coverage started, and the Division of Insurance turned it down as the first filing of its kind. Nothing on the shingles caused the losses behind that request.
An ice dam is a temperature problem wearing a costume. It needs three conditions at once: snow sitting on the roof, an outdoor temperature near or below freezing, and a roof deck that is warm in the middle and cold at the edge. Take away the third condition and the other two are harmless.
Step through it below. The house in the diagram is doing everything wrong on purpose.
Snow lands and stays. Six inches of snow is an insulating blanket. It holds whatever heat is coming up through the roof deck right against the shingles, which is why dams form during a cold snap after a storm rather than during the storm.
The eave is the part of the roof that hangs past the exterior wall. There is no heated room under it, so it sits at outdoor temperature no matter what the rest of the roof is doing. Water that melts higher up runs down, reaches that cold overhang, and stops being water. Repeat for two days and the ridge of ice is thick enough to pond meltwater behind it, and shingles are not designed to hold standing water. It finds the seams, then the sheathing, then the top plate, then your ceiling.
I need better gutters, or a roof that sheds ice.
Gutters do not cause ice dams and better ones do not stop them. A dam forms on the roof surface at the overhang, above the gutter, and would form on a house with no gutters at all. The gutter simply fills with ice first and gets the blame for being visible.
Roofing changes are a similar trap. Ice and water shield along the eaves is genuinely worth having, and it is required under the current code on new work, but it is a membrane that limits damage when water backs up. It does not stop the ice from forming. Replacing a roof to solve ice dams and leaving the attic alone buys a more expensive version of the same winter.
A ceiling is not a sealed lid. It is a plane with dozens of holes in it, and warm air under pressure from the stack effect goes through every one of them. The Building America Solution Center, run by Pacific Northwest National Laboratory for the Department of Energy, puts the fix in a fixed order: air seal the ceiling plane, insulate the attic, then ventilate the roof. Sealing comes first because insulation does not stop moving air, it only slows conducted heat.
These are the openings we find on nearly every house we scope in this area.
The gap where interior walls meet the ceiling drywall. Small individually, and there are dozens of feet of them.
Older non airtight fixtures vent room air straight into the insulation above them, warm and continuous.
The framed shaft around a masonry chimney runs from the basement to the ridge and is often open at the top.
Every vent stack and wire bundle has an oversized hole drilled for it that nobody ever closed.
A large uninsulated panel with no weatherstripping, sitting at the highest pressure point in the house.
The boxed ceilings over kitchen cabinets and bathtubs are usually open cavities connected to the attic.
Warm, wet air by design. This one adds a moisture problem on top of the heat problem.
The unsealed stud bays behind a finished half story pour heat into the eave, which is the worst possible place for it.
Ordering source: Building America Solution Center, attic air sealing, insulating, and ventilating for ice dam prevention.
Five statements a homeowner hears every winter. Pick one for each and the answer opens underneath.
Myth. Ventilation is the third step, not the first. Adding vents to an attic that is still leaking warm air can pull more conditioned air up through the ceiling and make the house colder without cooling the deck. Vents help once the ceiling is sealed and the insulation is at depth.
Mechanism. This is the whole cause. Heat from the house warms the underside of the roof deck, the snow melts from below, and the water refreezes where the deck is cold. Everything else is a symptom.
Myth. A brand new roof over a leaky ceiling dams exactly the same. We see it on houses that were reroofed the previous summer, which is usually the year the homeowner is most surprised.
Mechanism. Insulation slows conducted heat. It does nothing to air moving through a hole. A foot of new cellulose blown over unsealed top plates and open can lights will still pass enough warm air to melt snow.
Myth. Cables cut a channel through ice that has already formed, using electricity all winter to do it. They are a way to live with the problem, not a repair, and they add a running cost to a house that is already losing heat.
The order matters more than the materials. Doing step two before step one is the most common way a homeowner spends real money and still gets dams in January.
Every penetration listed above gets closed with foam, caulk, or rigid material depending on the opening and its fire rating. Chimney chases get sheet metal and high temperature sealant, not canned foam. This is whole-home air sealing, and through Mass Save the targeted portion of it is performed at no cost.
Bath fans and dryer runs that terminate in the attic get redirected to the outside. Recessed cans that cannot be buried get airtight covers. Both are cheap while a crew is up there and expensive as a return visit.
The perimeter is where dams start, so the insulation has to carry full depth out over the top plate rather than tapering away at the eaves. Baffles hold it back from the soffit vents while keeping the depth. Target R-49 to R-60 in this climate zone, which is covered in what attic insulation costs in Massachusetts.
Balanced intake at the soffits and exhaust at the ridge flushes the small amount of heat that still gets through, so the deck stays close to outdoor temperature. Ventilation is a finishing step. It cannot outrun a leaky ceiling.
Knee walls and sloped ceilings are their own job. On a cape or a colonial with a finished half story, the eave cavity behind the knee wall is often wide open to the soffit. Sealing and insulating those bays is hand work rather than hose work, and skipping it is why some houses get dams on one side of the roof only.
I will just get the ice off the roof.
Removing ice treats this week and guarantees next week. It is also where most of the secondary damage comes from, since the tools that break ice also break shingles.
Shingles are brittle at 20 degrees. Every strike that removes ice takes granules or a tab with it, and the leak moves from seasonal to permanent.
They cut a hole where they sit, then run corrosive meltwater across flashing, gutters, and whatever is planted below.
The most predictable injury of the New England winter. Anything that needs doing up there is worth a professional and a ladder set on cleared ground.
It can increase the flow of warm air out of the living space and leave the deck no colder than it was.
A roof rake used from the ground on the first three or four feet of the eave is the one exception. It removes the snow the dam needs without anyone leaving the driveway, and the Massachusetts Division of Insurance lists it among the steps homeowners can take before a claim happens.
Mid winter is not when the attic gets fixed, so the job in front of you is limiting damage and documenting it. In order: move what is under the leak and get a container down, then photograph the ceiling stain, the exterior eave, and the icicle line before anything melts. Call the insurer the same day rather than after it dries, because the claim turns on the damage being sudden.
Rake the snow off the lower few feet of the roof from the ground if you can reach it. If water is actively running into the house, an ice dam removal company using low pressure steam can open a drainage channel without damaging shingles, and steam is the only removal method worth paying for. Pressure washers and chippers do more harm than the dam.
Then put a note in your calendar for April. The attic work is a dry season job, it takes a day on most houses, and it is the only part of this that stops it happening again.
One thing to check inside. If the ceiling stain is at an exterior wall and the room above it is a finished half story, the water is likely coming through the knee wall eave rather than the main attic. Tell whoever scopes the job, because it changes where the work happens.
Standard Massachusetts homeowner policies generally cover interior water damage from an ice dam when the loss is sudden and accidental. The phrase carrying the weight is the second half. Damage traced to a lack of maintenance is where claims get denied, and the Division of Insurance is explicit that homeowners should have a professional evaluate the insulation and ventilation in the home as a preventive step.
That is a documentation problem as much as a building one. A house with a written assessment and completed air sealing and insulation work has evidence that the owner acted. A house on its third ice dam claim with no work performed between them is having a different conversation with the adjuster, and Mapfre's 2015 attempt at a separate ice dam deductible shows where the industry would prefer that conversation to end up.
The practical route in this state is the no-cost home energy assessment, which produces exactly that written record and also opens 75 to 100 percent off the insulation work through Mass Save. The assessment costs nothing and the report is yours whether or not you do the work.
Sources: Massachusetts Division of Insurance winter weather guidance, and Boston Globe reporting from December 2015 on the rejected ice dam deductible filing.
Two houses on the same street get the same snow and the same temperatures, so the difference is inside. Usually it is the number of openings in the ceiling plane, the depth of insulation at the eaves, or a finished attic space in one house and not the other. It can also be as specific as one house having six recessed lights in a cathedral ceiling and the other having none.
On most houses, yes, because the heat that drives the melting is gone. The honest exception is a roof with a complicated geometry, a valley that dumps snow onto a lower section, or a dormer arrangement that shades one plane and sunlights another. Those can still ice in an extreme winter, though far less and with far less water behind it once the attic is corrected.
Air sealing and attic insulation are interior work, so they can be performed in the cold. The limits are practical rather than seasonal. An attic packed with snow blown in through the soffits has to dry first, wet insulation has to come out, and a crew cannot assess a roof edge buried in ice. Booking the assessment in winter and the work for early spring is the usual sequence.
Complete Home Comfort scopes ice dam prevention work across Franklin and the surrounding towns, seals the ceiling plane before anything is blown, and handles the Mass Save paperwork as part of the job. Tell us what the roof did last winter and where the water showed up inside.
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