What is a composition roof?
Composition roofing is the asphalt shingle. What the shingle is made of, the three grades a homeowner gets quoted, and what changes through a Minnesota winter.
A composition roof is an asphalt shingle roof. “Composition” describes what the shingle is made of, a manufactured composite of a fiberglass or organic mat, asphalt, and mineral granules, rather than a single natural material cut from stone, wood, or clay. In the trade, “composition,” “comp roof,” and “asphalt shingle” all mean the same product, and a quote that uses any of the three is quoting the same shingle.
What is actually in a composition shingle
A composition shingle is built in layers, and each layer does one job. At the center is the mat, either fiberglass or an organic felt, which gives the shingle its shape and its tear strength. That mat is saturated and coated with asphalt, which is what makes the shingle waterproof, and the asphalt is what “composition” is naming when it says the material is a composite rather than a single substance. On top of the asphalt sits a layer of mineral granules, and on the underside of most shingles is a strip of self-sealing adhesive that bonds to the course below once it warms in the sun, which is what keeps a properly installed shingle from lifting in wind. Take any one of those layers out and what is left is not a functioning shingle. The mat without asphalt has no waterproofing. The asphalt without granules degrades in sunlight within a season or two. The whole point of the composite is that no single material in the stack has to do every job.
Why the granules matter more than the color
The granules are there to block ultraviolet light from reaching the asphalt underneath, and the color is a side effect of that job, not the reason for it. Raw asphalt breaks down under UV exposure. It dries out, cracks, and loses flexibility within a few years of direct sun. The mineral granules pressed into the surface coat absorb and reflect that UV load instead, which is what lets the asphalt layer underneath stay flexible for the life of the roof rather than the life of one summer. This is also why granule loss is the sign roofers watch for on an aging roof. Bare patches where granules have worn away or washed into the gutters are not a cosmetic issue. They are asphalt losing its shield, and that spot will age faster than the rest of the field.
Three-tab, architectural, and premium: what actually changes between them
A homeowner shopping composition roofing gets quoted one of three grades, and the difference between them is thickness, not just looks. Three-tab shingles are a single layer, flat, uniform, and the lightest of the three, which also makes them the least wind-resistant and the shortest-lived of the grades. Architectural shingles, also called dimensional, are laminated from two layers, which gives them more thickness, a shadow-line appearance instead of a flat one, meaningfully better wind resistance, and a longer service life than three-tab. Premium or designer shingles add another step, built heavier still and often profiled to read as slate or heavy wood shake from the street, with the wind resistance and lifespan that comes with the added mass and construction. Weight climbs in the same order: three-tab is the lightest per square, architectural sits in the middle, and premium shingles are the heaviest, which is worth knowing before assuming any composition roof can go on any structure without a second look at what the framing already carries. Architectural has become the default quote on most homes for a reason: it is the point on that curve where wind resistance and appearance improve substantially over three-tab without the weight and cost jump that premium brings.
Impact-rated shingles are a separate question from grade
None of those three grades automatically means impact-resistant, and in a hail state that distinction is worth asking about directly. Impact resistance is a separate rating, most commonly Class 4 under the standard testing method, that measures how well a shingle resists cracking and mat fracture when struck, and it is available across multiple grades rather than being a synonym for “premium.” A three-tab shingle and an architectural shingle can each come in an impact-rated version, and an architectural shingle can be sold with or without one. Since hail is a real exposure across the Twin Cities north metro, asking specifically whether a quoted shingle carries an impact rating, rather than assuming a heavier or better-looking shingle automatically has one, is worth the one extra question.
Organic mat versus fiberglass, and why fiberglass took over
Composition shingles used to be built on an organic felt mat, cellulose fiber saturated with asphalt, and most of what gets installed today uses a fiberglass mat instead. Fiberglass took over for a few concrete reasons: it does not absorb water the way organic felt does, so it holds its shape and resists the internal decay that eventually caused organic-mat shingles to curl and split from the inside. It is also lighter for the same fire and strength rating, and it is more dimensionally stable across temperature swings, which matters directly in a climate that moves through a wide range across one winter. Organic-mat shingles are still made and still installed in some markets, but on a new composition roof in this region, fiberglass is what is typically going down, and it is worth confirming which mat a quote is actually specifying rather than assuming.
Why composition roofing covers most of the market
Composition dominates residential roofing for reasons that have nothing to do with it being the best material by every measure and everything to do with it being the best fit for the most houses. It costs less to produce and install than metal, tile, or slate. It is light enough that most existing roof framing can carry it without the structural reinforcement that heavier materials like slate or tile often require, which matters on an older home where nobody wants to open up the framing to find out. It is easy to repair in sections, a single damaged area of shingles can be replaced without touching the rest of the roof, where a section of standing-seam metal or a broken tile is a more specialized fix. And it comes in enough colors, profiles, and grades that it can be matched to nearly any architectural style, from a plain rambler to a home built to look like it is wearing slate. No other roofing material clears all four of those bars at once, which is the actual explanation for why most of the roofs on most streets are composition.
What composition roofing does not do well
The honest tradeoff is service life and vulnerability. Composition shingles have a shorter service life than metal, tile, or slate, which routinely outlast them by a wide margin, and that gap is the real cost of the lower upfront price and lighter weight. Composition is also more vulnerable to hail bruising than harder materials, since a hard enough impact can fracture the mat under the granules even when the surface looks intact from the ground, which is why a pre-winter inspection catches problems the ground view misses even on a roof with no visibly missing shingles. And the performance of the shingle itself depends heavily on two things that are not the shingle: attic ventilation and installation quality. A well-made shingle installed over a poorly ventilated attic, or installed with the wrong nailing pattern or the wrong flashing details, will underperform its own design life regardless of grade or brand. The shingle is one part of a system, and treating it as the whole system is where a lot of premature roof problems start.
How a composition roof actually performs through a Minnesota winter
The two things that matter most here are thermal cycling and what happens at the eave, and neither one is about which shingle is on the roof. Minnesota roofs move through a wide temperature swing across a single winter, sometimes within one day, and that expansion and contraction is what eventually stresses fasteners, seams, and flashing more than straight-line cold does on its own. The eave is where a Minnesota roof does its real work in winter: attic heat that escapes into the roof deck melts snow above the warm part of the attic, that meltwater runs down to the cold overhang past the heated wall line, and refreezes there, which is how an ice dam forms regardless of shingle grade. The two things that actually control that outcome are attic ventilation, which keeps the underside of the deck close to outdoor temperature so there is less melting to begin with, and the ice barrier membrane required at the eave, which is what stands between refrozen meltwater and the wall cavity if a dam forms anyway. The code requirement for that membrane, and how the industry actually verifies it on a job, is its own subject. The shingle brand on a Minnesota roof matters far less to winter performance than whether the attic behind it is ventilated correctly and whether that eave detail was done right.
What to look for on an estimate that says “composition”
Two estimates can both say “composition” or “architectural shingle” and still describe two different roofs, because the word only names the shingle, not the assembly around it. Ask what grade is actually specified, three-tab, architectural, or premium, since the word “composition” alone does not tell you which. Ask what underlayment is going down under the shingles, since synthetic and felt underlayments are not interchangeable and a proposal that does not name one is missing a real line item. Ask specifically about the ice barrier membrane at the eaves, since it is required and is one of the parts of the job nobody can verify after the shingles go on. Ask how the roof is ventilated, since a beautiful shingle over a hot, damp attic will not hold up on schedule. And ask about the fastener pattern, since nailing a shingle correctly, the right number of nails in the right zone of the shingle, is a large part of what its wind rating assumes and is invisible once the roof is finished. None of those five questions is about price. All five are about whether the roof performs the way the shingle’s own rating assumes it will.
If you have an estimate in hand and it just says “composition roof,” that is a starting point, not a finished spec. A roof inspection that looks at the current deck, attic ventilation, and eave condition is what turns “composition” into a specific, checkable plan for your house, and it is worth asking your roofer to walk through the grade, underlayment, ice barrier, and ventilation choices by name before anything goes on the roof.