Ice Dams: What to Do Now, and How to Stop Them Next Winter

Why Ice Dams Form

An ice dam is a ridge of ice at the edge of the roof that keeps melting snow from draining off. The water backs up behind it and can leak under shingles into the attic, walls and ceilings.(UMN Extension)

• Three ingredients: snow on the roof, an attic that leaks or lacks insulation, and freezing weather.(DOE Building America) The upper roof sits above 32°F while the edge, out past the heated walls, stays below it.
• The heat comes from the house, rarely the sun. In many homes it's mainly warm air leaking through the ceiling, around light fixtures, chimneys, ducts and bath fans.(UMN Extension)
• It doesn't take much snow: dams can form under as little as 2 inches. Snow also insulates the roof, about R-1 to R-2 per inch, so deeper snow makes it worse.(DOE Building America)
• Gutters aren't the cause. Dams form on roofs without gutters too.(NRCA) But ice packed in a gutter can still back water up at the eaves, so clear and slope gutters before winter.(NRCA)

Madison averages 51.8 inches of snow a year, most of it from December through February, and the average first inch falls around November 25.(National Weather Service)

Signs to Look For

• Icicles along the roof edge or gutters, ice coming through the soffit, and water or ice on an outside wall.(Focus on Energy)
• Bare patches on a snowy roof, with icicles below them: heat from the room underneath is warming the roof.(DOE Building America)
• Stains on ceilings or at the top of exterior walls.(UMN Extension) In the attic: damp insulation, or insulation darkened where air has been leaking through it.(ENERGY STAR)

When You Have One Now

• Rake the lower roof from the ground. Wisconsin's insurance commissioner suggests a roof rake or push broom on the first one or two feet. Rake sparingly to protect the shingles.(Wisconsin OCI)
• Stay off the roof. Falls cause the most deaths and injuries in rooftop snow removal. Take small amounts at a time so falling snow can't bury you, and keep metal rakes away from power lines.(OSHA)
• Don't chip the ice with picks, hammers or shovels. It damages shingles and gutters.(Wisconsin OCI)
• Keep people out from under icicles. They can fall and injure someone.(DOE)
• If water is coming in, Minnesota's energy office says to hire an ice dam removal service that uses steamers rather than chippers, chemicals or heat.(Minnesota Dept. of Commerce) UMN Extension describes cutting channels through the dam with a garden hose on a warm day as a short-term emergency fix that stops working within days.(UMN Extension) NRCA doesn't recommend hosing a roof.(NRCA)
• Salt: sodium chloride runoff can stunt or kill plants below the eaves.(UW Extension, Dane County) NRCA says calcium or magnesium chloride is gentler on roofing, but melting products can stain.(NRCA)
• Roof-vented furnace or water heater: keep the vent clear of snow. If it's buried, the appliance may need to be shut off until it clears.(National Weather Service)
• After a leak: dry wet areas right away to head off mold, and wait until ceilings and walls are dry before repairing them.(UMN Extension)

Clearing ice treats the symptom. The dam comes back every winter until the heat loss is fixed.

Fixing the Cause: Air Sealing, Insulation, Venting

The goal is a cold roof: keep the house's heat out of the attic so the whole roof stays as cold as its edge.(Wisconsin OCI)

1. Seal air leaks first. Federal Building America guidance calls it the most important step, and UMN Extension says make the ceiling airtight before adding insulation.(DOE Building America) Common leaks: the attic hatch, holes for wiring and plumbing stacks, recessed can lights, dropped soffits, chimney and flue chases, exhaust fan housings, and the tops of interior walls.(ENERGY STAR)
2. Seal around chimneys and flues the right way: sheet metal and high-temperature caulk, not spray foam. Codes usually require 1 inch of clearance to metal flues and 2 inches to masonry chimneys.(ENERGY STAR)
3. Vent bath, kitchen and dryer fans outdoors, not into the attic. Fix those before attic insulation work.(ENERGY STAR)
4. Then insulate. ENERGY STAR recommends R60 for an uninsulated attic in Madison's climate, or adding R49 if you have 3 to 4 inches now.(ENERGY STAR) The roof edge matters most: insulation should run at full depth out over the top of the exterior walls.(DOE Building America) Keep insulation 3 inches from can lights unless they're rated IC.(ENERGY STAR)
5. Keep the soffit vents open. Never cover them with insulation; use baffles (rafter vents) to hold an air channel open.(ENERGY STAR) Ventilation helps, but it isn't a fix on its own.(NRCA) UMN Extension doesn't recommend powered attic fans for ice dams.(UMN Extension)
6. Ducts and furnaces in the attic add heat right under the roof. Keep equipment out of the attic where possible; ducts that must be there should be sealed and buried in insulation.(DOE Building America)

• Before anyone disturbs old insulation: vermiculite (grayish-brown pebbles) may contain asbestos. Have it tested first.(ENERGY STAR)
• Get a blower door test. UMN Extension suggests hiring a contractor who measures leakage with a blower door, sometimes with an infrared camera. A tighter house also has to leave furnaces, water heaters and exhaust fans enough air to run safely.(UMN Extension)
• Wisconsin's building code for new homes requires attic venting designed to prevent ice damming (SPS 322.39), and insulation that keeps its full depth over the wall plate at the eaves.(Wis. Admin. Code SPS 322)

Rebates for Insulation and Air Sealing (2026)

Focus on Energy, the statewide program funded by Wisconsin utilities, names insulation and air sealing as the fix for ice dams.(Focus on Energy) Its 2026 single-family rebates, for work done on or after January 1, 2026:

• The insulation has to be installed by a participating Focus on Energy Trade Ally contractor. Focus says the energy assessment that unlocks the air sealing rebate typically costs $500 to $700.(Focus on Energy)
• Doing it yourself: a $200 rebate for attic air sealing and insulation done together, covering at least 600 square feet and reaching R-42 or more.(Focus on Energy)
• Deadlines: the program's web page and its 2026 flyer list different application deadlines. Check the current date with Focus on Energy (800-762-7077) before you start.(2026 flyer)
• A home that got a Focus rebate in the same category in the past three years doesn't qualify again.(Focus on Energy)
• Federal home energy rebates (HOMES and HEAR) also run through Focus on Energy and cover insulation and air sealing. HEAR is for households at or below 150% of area median income. Both require an IRA-registered contractor.(Focus on Energy)
• MG&E customers are sent to Focus on Energy for these incentives.(MG&E)
• The federal tax credit for insulation (25C) covers only work done through December 31, 2025.(IRS)

Roof Edge Protection and Wisconsin Code

An ice barrier (often called ice and water shield) is a self-sticking membrane laid under the shingles along the eaves. It seals around nails so water backed up behind a dam is less likely to get through. It reduces leaks; it doesn't stop dams from forming.(NRCA)

• Wisconsin's code (SPS 321.28(4)) requires ice dam protection on shingle or shake roofs over heated space only when the slope is 4:12 or less, that is, 4 inches of rise per foot or flatter. It must reach at least 30 inches up from the roof edge and 12 inches past the inside of the exterior wall.(Wis. Admin. Code SPS 321)
• Manufacturers and NRCA go further. Owens Corning's instructions run its barrier from the eave to 24 inches inside the exterior wall.(Owens Corning) NRCA recommends at least that, and 36 inches on low slopes or in heavy-snow areas.(NRCA) If you're reroofing, ask what the bid includes at the eaves.
• New shingles can't go over a roof that's water-soaked or deteriorated, or that already has two or more layers.(Wis. Admin. Code SPS 321)
• Madison permits: replacing a roof needs a building permit; repairs under $500 don't. You can check that a permit was pulled at Building Inspection, 608-266-4551 ext. 1. When the roof comes off, check the house for water damage.(City of Madison) A reroof without structural changes can be applied for online.(City of Madison)

Town-by-town permit rules for other projects are in the remodel permit guide.

Heat Cables

• What they do: keep a heated channel open so meltwater can drain. Their makers say they don't melt snow or ice that has already built up.(Raychem)(Easy Heat)
• What others say: Minnesota's energy office says not to install them.(Minnesota Dept. of Commerce) NRCA advises against them because of electrical risk, roof damage from fastening, and no protection when they fail.(NRCA)
• Safety: the circuit needs ground-fault protection, because a damaged cable may not trip an ordinary breaker. Easy Heat's plug-in kit is for sloped shingle roofs and gutters only, not metal roofs.(Easy Heat)
• Power: Easy Heat's ADKS cable draws 5 watts per foot while it's on. A cable left off when it's needed lets ice form; one left on when it isn't wastes power.(Raychem)

Insurance

• Wisconsin's insurance commissioner says water from the top down, including ice dam seepage, is generally covered by a standard homeowners policy. A roof already in poor condition can affect coverage.(Wisconsin OCI) Damage from neglect isn't covered, and coverage varies by company.(OCI homeowners guide)
• If you have a leak: notify your agent or company right away, photograph damage before cleanup, keep receipts, and don't throw out damaged items until the adjuster agrees.(Wisconsin OCI)
• Make temporary repairs to stop more damage, but wait for the adjuster before permanent repairs.(OCI claims guide)
• Questions or a complaint about an insurer: the Office of the Commissioner of Insurance, 1-800-236-8517.(Wisconsin OCI)

Hiring a Roofer or Insulation Contractor in Wisconsin

Roofing and insulation work fall under Wisconsin's home improvement rule (ATCP 110):(ATCP 110)

• If you pay anything before the work is done, you need a written contract. The contractor must tell you about required permits before you sign. A Madison reroof needs one.
• It's illegal for a contractor to falsely tell you your roof or attic is defective or needs replacing.
• A contractor pulling a permit on a one- or two-family home needs a state Dwelling Contractor credential, which requires a $25,000 bond or $250,000 of liability insurance.(DSPS)
• If it's an insurance job: a contractor can't promise to pay your deductible or negotiate with your insurer for you, and must tell you about your right to cancel within three business days if the insurer denies any part of the claim.(DATCP)
• Avoid door-to-door crews after storms. Get lien waivers with each payment, and have the building inspector check the work before you make the final payment.(DATCP)
• For insulation rebates, the installer has to be a Focus on Energy Trade Ally (see Rebates).
• Check a company's complaint history with DATCP's Consumer Protection Hotline, (800) 422-7128, and ask for a certificate of insurance that names you as the holder.(DATCP)

Questions

What causes ice dams?

Heat from the house warms the upper roof above freezing while the roof edge stays below freezing. Snow melts higher up, runs down and refreezes at the cold edge, building a ridge that traps the next meltwater. In most homes, warm air leaking into the attic is the main source of that heat.

Do gutters cause ice dams?

No. Ice dams form on roofs without gutters too. Ice packed in gutters can still back water up at the roof edge, so keep gutters clear and sloped to drain.

Should I use a roof rake?

Wisconsin's insurance commissioner, UMN Extension and OSHA all suggest raking the lower few feet of roof from the ground. Do it sparingly: rakes can damage shingles, and NRCA notes that snow left higher up can form a new dam above the cleared strip.

Does homeowners insurance cover ice dam leaks in Wisconsin?

Wisconsin's insurance commissioner says water from the top down, including ice dam seepage, is generally covered by a standard homeowners policy, but a roof already in poor condition can affect coverage. Policies vary, so check yours. Call your agent right away and photograph the damage before cleanup.

Do heat cables prevent ice dams?

They keep a channel open for meltwater; they don't stop the melting that causes the dam, and their makers say they don't melt ice that has already built up. Minnesota's energy office and NRCA advise against them.

How much attic insulation do I need in Madison?

ENERGY STAR recommends R60 for an uninsulated attic in Madison's climate, or adding R49 if you already have 3 to 4 inches. Seal the air leaks first: federal and university guidance both call air sealing the most important step.

Is there a rebate for attic insulation in Wisconsin?

Yes. Focus on Energy's 2026 attic insulation rebate is $650 to $850 depending on household income, installed by a participating contractor, with larger rebates for air sealing after an energy assessment. There's also a $200 do-it-yourself rebate. The federal tax credit for insulation ended for work after December 31, 2025.