This is the page where we talk you out of work. The Minnesota Department of Commerce is explicit that ice dams are not caused by roofing, ventilation or gutters, and that adding roof vents often makes them worse. If somebody is selling you vents to fix ice dams, here is the state’s own guidance.
Ice dams come from warm air leaking out of your house into the attic, melting snow from underneath. The melt runs down and refreezes at the cold eave. The Minnesota Department of Commerce says plainly that roofing, ventilation and gutters are not the cause, that adding roof vents “will not eliminate ice dams and often make the problem worse,” and that the fix is air sealing plus insulation to R-50. The roof is where you see the symptom, not where the problem is.
Heat escaping from inside the house into the attic. It warms the underside of the roof deck and melts the snow lying on it. That meltwater runs down the roof until it reaches somewhere cold — the eave or the soffit, which overhang unheated space — and freezes there. Repeat over a cold snowy week and the ridge of ice grows until water backs up behind it and finds a way in.
This is why ice dams form on some houses and not on their neighbours in the same weather, and why they often recur in the same spot every year. It is tracking where your house leaks heat.
Minnesota Department of Commerce: “Ice dams are not caused by roofing, ventilation or gutter problems, as often believed. The real problem is a home that is leaking warm air. Due to inadequate air sealing, heat from the home’s interior gets into the attic and melts the underside of the snow on the roof.” Source: MN Dept. of Commerce, Minnesota Energy Tips
The Department of Commerce says no, and says it can make things worse. This is worth stating plainly on a roofing company’s website, because added ventilation is a common upsell on a re-roof and it is sold as an ice dam remedy more often than it should be.
Ventilation has real purposes — it manages moisture and heat in the attic, and the building code requires it. Curing ice dams is not among them. A powered vent can actively draw more warm, moist house air up into the attic through the same gaps that caused the problem.
If you are re-roofing anyway, ventilation should be brought to code because it is required and because it protects the deck. Just do not buy it as an ice dam cure.
Minnesota Department of Commerce: “Do not add roof vents, including powered vents. They will not eliminate ice dams and often make the problem worse.” Source: MN Dept. of Commerce, Minnesota Energy Tips
Sealing the air leaks between the heated house and the attic, then insulating. The Department of Commerce gives a specific target: seal with caulking or expanding spray foam, with attic insulation to a minimum of R-50 as space allows.
The leaks are usually in predictable places — around plumbing vent stacks, chimney chases, recessed lights, bath fans, the top plates of interior walls and the attic hatch. They are small and unglamorous and they are the whole problem.
Commerce recommends starting with a home energy assessment, which uses an infrared camera to find the leaks rather than guessing, and then getting bids from at least two licensed contractors. A home energy audit can be arranged through your utility, a nonprofit energy group, or an HVAC professional.
Minnesota Department of Commerce: “Because the primary cause of ice dams is warm air leaking from the attic, the best prevention is to seal leaks with caulking or expanding spray foam, with attic insulation installed to a minimum of R-50 as space allows.” Source: MN Dept. of Commerce, Minnesota Energy Tips
Commerce names three things specifically. Do not install heating cables — they shorten the life of the roof and add to energy costs. Do not remove ice with chippers, chemicals or heat, which damage shingles, gutters and other building components. And do not add roof vents.
If an ice dam is already pushing water into your ceilings and walls, the state recommends hiring a professional removal service that uses steam. Steam melts the ice without hammering the roof it is sitting on.
Prevention through the winter can include pulling snow off the roof with a snow rake, which Commerce suggests; it also notes it may be better to hire someone, particularly if the job means a ladder or getting on the roof.
Minnesota Department of Commerce: “Do not install heating cables. They will shorten the life of your roof and add to your energy costs. Do not remove ice with chippers, chemicals or heat. These can damage shingles, gutters and other building components.” Source: MN Dept. of Commerce, Minnesota Energy Tips
Because the code is not trying to prevent the dam. It is limiting the damage when one forms anyway. The ice barrier is a waterproof membrane under the shingles along the eave, so that water backing up behind an ice ridge runs over a sealed surface instead of through the deck into your ceiling.
It is insurance against a condition the code assumes will occur, which is exactly the right way to think about it. Sealing and insulating stops the dam forming; the ice barrier stops the dam that forms anyway from costing you a ceiling. They are not alternatives.
How far the barrier must run is the single most common place two Minnesota roof quotes quietly differ. We wrote that up separately with the code text.
City of Burnsville, re-roofing requirements: “The Minnesota building code requires that an approved ice barrier underlayment be installed from your roofs edge to a point at least 24 inches past the exterior wall line. This applies to all portions of your roof, including attached heated or un-heated garages, covered porches, bays, fire place enclosures and similar areas.” Source: City of Burnsville, Re-Roofing With Asphalt Shingles
This page quotes Minnesota statutes and the adopted Minnesota building code and links to the official text of each so you can read it yourself. It is general information from a licensed contractor, not legal advice, and it is not a substitute for reading your own policy. Statutes and codes are amended; the linked sources are authoritative, this page is not. Last reviewed 2026-10-27.
Straight answers to the questions Minnesota homeowners ask before they call anyone.
The Minnesota Department of Commerce puts the target at a minimum of R-50 in the attic, with air leaks sealed first using caulking or expanding foam.…
Read the guide →Ice dams form because warm air leaks out of your house into the attic and melts snow from underneath. The Minnesota Department of Commerce states…
Read the guide →A Minnesota contractor cannot pay or waive your deductible, cannot interpret your policy for you without a public adjuster license, and must hand you…
Read the guide →Minnesota requires an ice barrier running from the eave to a point at least 24 inches inside your exterior wall line — measured inside the wall, not…
Read the guide →Costs, materials, timelines, financing, and how we work — across roofing, siding, windows, and gutters.
Read the FAQ →We’ll walk it, photograph it, and give you a written scope that says exactly what is required and why. Retail or insurance.
We’ll walk the roof, photograph what we find, and hand you a written scope that names the code requirement behind every line. Yours to keep, whoever does the work.
We measure the work by how it holds up — and by what clients say once we're gone.