Roof Underlayment for Cold Climates: Felt vs Synthetic

Most roofing gets installed in the comfortable months, and most underlayment comparisons are written for that weather: warm decks, dry air, a crew moving at a normal pace. Macomb County roofs do not only face those conditions after the shingles go on. A reroof scheduled in late fall, an emergency tear-off after a spring wind event, or simply a roof that has to survive a Michigan winter every year of its life all put underlayment through a colder, wetter, more demanding version of its job than the sales brochure usually describes. This guide compares asphalt-saturated felt and synthetic underlayment specifically on the traits that change in cold weather, and explains how underlayment works alongside the ice barrier membrane at the eaves and valleys rather than in place of it.

This is a materials-education page, not a pricing or installation guide. For the full breakdown of what underlayment is, what it is not, and what a quote line should say, start with our underlayment explainer. This page picks up where that one leaves the felt-versus-synthetic question and goes deeper on the specific behaviors that matter once the temperature drops.

01 / THE SHORT ANSWERSynthetic generally has the edge in cold weather

Both felt and synthetic underlayment are legitimate, code-recognized materials, and both do the core job described in our underlayment guide: catching wind-driven rain and protecting the open deck during a tear-off. In cold-weather conditions specifically, synthetic underlayment tends to hold an edge on three traits that matter most in a Michigan winter: it resists tearing better in high wind, it handles freeze and thaw moisture cycling without wrinkling the way felt can, and it gives a roofing crew steadier footing on a deck that is cold, damp, or lightly frosted. Felt remains a defensible, code-compliant choice, particularly on smaller jobs installed in milder weather, but it is doing its job under more stress the colder and windier the install day gets.

None of this makes felt the wrong choice on every job. A well-installed felt roof performs for decades, and the material has the longest track record in the trade. What changes in cold weather is the margin for error: synthetic gives a crew more room to work safely and correctly when the conditions themselves are working against a clean installation.

02 / THE MATERIALSTwo materials built for the same job, different ways

Felt underlayment, sometimes called tar paper, is an organic or fiberglass mat saturated with asphalt and sold in rolls graded by weight per roofing square. Synthetic underlayment is a woven or coated polymer sheet, usually packaged in rolls that cover more area per roll than felt of a comparable weight. Both are fastened directly to the wood deck before the shingles go down, and both are recognized by shingle manufacturers whose workmanship warranties cover the roof.

Why the difference shows up more in winter

In mild, dry weather, felt and synthetic behave more alike than their reputations suggest. Both shed water, both lap correctly, and both protect a deck that is being covered within a normal working day. Cold weather introduces three specific stresses that a summer install rarely sees at the same intensity: sustained high wind before the shingles are on, repeated freeze and thaw moisture cycling on a deck that may sit open longer than planned, and a walking surface that can carry frost or condensation even when it is not actively precipitating. Those three stresses are exactly where felt and synthetic start to diverge, which is the subject of the next three sections.

03 / WIND AND COLDTear resistance when the wind is up and the material is cold

Wind and low temperature interact with underlayment in a way that matters most during the window between tear-off and dry-in, when a sheet of underlayment on an open deck has nothing but its own fasteners holding it against the weather. Felt, an asphalt-saturated mat, tends to become noticeably stiffer and more brittle as the temperature drops, and a stiffer material is generally more prone to cracking or tearing at fastener points when wind loads it repeatedly. Synthetic underlayment, built from polymer rather than an asphalt-saturated mat, generally retains more flexibility in cold conditions and typically carries a higher rated tear strength to begin with, which is one reason many manufacturers and crews prefer it for late-season or early-spring work when a stretch of high wind is a real possibility before the roof is closed in.

This matters practically, not just on a spec sheet. A torn or lifted section of underlayment on an open deck during a cold, windy stretch is exactly the kind of gap that turns a routine tear-off into an emergency call. Crews scheduling cold-weather work account for this by limiting how much deck they open at once and by choosing materials rated to hold up if the weather window closes faster than planned, which is one more reason synthetic tends to be the default specification on jobs scheduled into the shoulder seasons.

04 / FREEZE AND THAWMoisture behavior through repeated freeze and thaw cycles

Macomb County winters do not deliver one long cold snap. They deliver dozens of freeze and thaw swings between November and March, and any underlayment left partially exposed, or installed under a shingle system that is still settling into its final seal, experiences some of that cycling directly. Felt has a known practical weakness here: if it gets wet and is then exposed to sun or dries unevenly before the shingles go on, it can wrinkle, and once a felt sheet wrinkles it rarely lies flat again, which can telegraph a faint ripple through the shingles installed over it. A synthetic sheet is generally far less prone to that wrinkling behavior, because the polymer face does not absorb water into its structure the way an asphalt-saturated mat can.

Underlayment is also handling a slower, less dramatic form of moisture: condensation forming on the underside of the deck in a poorly ventilated attic, or meltwater from a cold eave working back toward the field of the roof before it reaches the ice barrier zone. Our roof deck moisture guide covers what chronic dampness eventually does to the wood underneath; underlayment's role is limited to giving that moisture somewhere to go besides directly into the deck, and a material that stays flat and fully lapped through repeated wet-dry cycling does that job more reliably over the life of the roof than one prone to wrinkling.

What underlayment does not do

Neither felt nor synthetic underlayment is designed to hold back standing water the way a self-adhering ice barrier membrane is. Underlayment sheds water moving in one direction, downhill, shingle course over shingle course. When an ice dam forms and water backs up under the shingle line under pressure, ordinary underlayment is not the layer built to stop it, which is exactly why code requires a different, more aggressive membrane at the eaves. Section 06 covers how that division of labor works.

05 / FROSTY FOOTINGWalkability on a cold or frosted deck

The least-discussed cold-weather trait is also one of the most practical: how safely a crew can walk the surface while installing it. A bare wood deck in cold weather can carry a thin layer of frost or condensation even on a day with no active precipitation, simply because the temperature differential between the cold outside air and any residual moisture in the wood is enough to produce it. Felt underlayment, once installed, tends to offer less secure footing in those conditions, particularly if any moisture has reached the surface before the crew walks it. Synthetic underlayment is generally manufactured with a textured or non-slip surface specifically because footing is a known concern, and most crews report noticeably more confident footing on synthetic during marginal-weather installs.

This is a crew safety question first, but it is also a workmanship question. A crew moving cautiously across an unstable surface works more slowly and is more prone to small installation errors, misaligned laps, under-driven fasteners, than a crew with secure footing. On a cold, frost-prone install day, the underlayment choice can quietly affect the quality of everything installed on top of it, which is one more reason the material spec matters more in winter than the underlayment aisle at a supply house might suggest.

06 / THE DIVISION OF LABORHow underlayment teams with the ice barrier at eaves and valleys

Neither felt nor synthetic underlayment is a substitute for the self-adhering ice barrier membrane Michigan code requires at the eaves, and Macomb County sits squarely inside the region where that requirement applies. The two products are not competing for the same job; they are dividing one continuous problem into two zones with different failure modes.

Across most of a roof's surface, felt or synthetic underlayment handles ordinary wind-driven rain and protects the deck during installation, the way described in sections 03 through 05. At the eaves, in valleys, and around penetrations like chimneys and skylights, water behaves differently in a Michigan winter: it can pond under an ice dam and get pushed uphill, under pressure, into places gravity-fed underlayment was never engineered to resist. That is the specific job of the self-adhering ice barrier membrane, which seals tightly around every fastener that passes through it. Our ice and water shield guide covers that membrane, the code requirement behind it, and exactly where it belongs beyond the eaves in full detail.

A well-built Macomb County roof always has both products working together: field underlayment across the general roof area, and the eave membrane layered in at the high-risk zones. A quote that only specifies one or the other is missing half the system. The eave membrane's placement and how far up the slope it needs to run is its own detailed question, covered in our drip edge and ice barrier guide, and how the two systems interact with a properly ventilated attic to actually reduce ice dam formation, rather than just contain the damage after the fact, is covered in our guide on whether a new roof alone stops ice dams.

Underlayment protects the field of the roof from ordinary weather. The eave membrane protects the places a Michigan winter turns ordinary weather into standing water under pressure. A cold-climate roof needs both, specified correctly, not one in place of the other.

07 / THE QUOTEWhat a cold-climate quote should specify, and getting it verified

Underlayment is included in the base price of every full replacement we quote in Macomb County, the same as tear-off, flashing, ventilation, and the ice barrier membrane at the eaves. A full asphalt shingle replacement here runs $9,000 to $18,000 installed, and most homes land $12,000 to $16,000, a figure that already assumes both the field underlayment and the eave membrane are done correctly, not as separate add-ons. What is worth asking a contractor directly, especially for a reroof scheduled into a cold or windy stretch of the calendar, is which underlayment family they specify and why, and whether the eave and valley membrane placement accounts for your roof's specific pitch and overhang.

The only way to know what is currently on your roof, or to get a specific recommendation for a planned reroof, is a free inspection that gets someone onto the deck and, where relevant, into the attic. Our inspection is $0 with no obligation, and on a replacement estimate we tell you the underlayment and eave membrane plan we recommend and why, not just a total. If you want a ballpark before anyone visits, the instant estimator runs the same published price canon shown here, and the cost calculator applies those ranges to your own roof size.