Two identical roofs put on the same day will age very differently depending on where they are. Gonano compares Phoenix with Winnipeg. We'd say a roof in Cranbrook gets a bit of both: hot, dry, high-sun summers and long winters that freeze and thaw over and over.
Why Climate Sets the Clock
Shingles rely on the oils in the asphalt to stay flexible and shed water. Heat, UV, cold and moisture all draw those oils out. Once they're gone, the shingle can't bend with the weather any more, so it cracks instead. That's why so few roofs make it to the top of their rated lifespan.
Sun and Heat
Summer sun in the valley is strong, and long days give it plenty of hours on your roof. Heat and UV dry out and harden the shingles, and the south- and west-facing slopes age fastest. Dark shingles run hotter still. Then there's the swing between a 30-degree afternoon and a cool mountain night: the shingles expand and contract every day, and that movement slowly opens cracks.
Freeze-Thaw and Snow
This is the big one here. Water gets into a hairline crack, freezes, expands and widens it, then thaws and does it again, sometimes dozens of times in a winter. A sunny afternoon in January can melt the snow off a south slope by lunch and refreeze it by supper. A flexible shingle moves with that. A brittle one cracks, and every crack lets in more water for the next freeze. Snow load and ice along the eaves add to it, which is why a roof that's already aging is most at risk going into winter. Our fall roof-prep checklist covers what to do before the snow flies.
Hail and Wind
Summer storms through the valley can bring hail that bruises shingles and knocks off granules, and the wind that comes down the Rocky Mountain Trench lifts and flexes tabs, tearing at edges and corners. A brittle roof absorbs that kind of punishment poorly. Our hail, wind and fire article explains what the ratings on a treated roof mean.
Moss and Shade
We're drier than the coast, but roofs under big firs and pines, or on shaded north slopes, can still grow moss and algae. That growth holds moisture against the shingles, speeds up granule loss and lifts edges. It's damage, not just a stain.
How to Slow It Down
- Keep gutters clear so meltwater can drain instead of freezing and backing up under the shingles.
- Ventilate the attic so the roof deck stays evenly cold in winter and cooler in summer.
- Deal with moss and algae early.
- Restore the shingles before they turn brittle. Rejuvenation puts flexibility back into aging shingles, and timing matters: treat before the hard freezes in fall or ahead of the summer heat, after a free assessment. The treatment needs dry weather above freezing, so if this fall's window has closed, book now for spring.
Want the Full Guide?
This is the short, local version. For the complete guide, read Gonano's article: How Climate Extremes Shorten Your Asphalt Roof's Life.
Frequently Asked Questions
How does climate affect how long a roof lasts?
Climate is the main reason roofs fall short of their rated lifespan. Heat, UV, cold, freeze-thaw and moisture all draw out the oils that keep shingles flexible, so they turn brittle and crack.
What is freeze-thaw damage?
Water gets into small cracks, freezes and expands, then thaws, over and over through the winter. Each cycle widens the crack, and hairline cracks can turn into leaks.
Which is harder on a roof, heat or cold?
Both shorten roof life. Heat and UV dry shingles out, cold and freeze-thaw crack them, and both speed up the loss of oils. East Kootenay roofs get a full dose of each.
Do moss and algae damage a roof?
Yes. They hold moisture against the shingles, speed up granule loss and lift the edges, so they should be dealt with early.
Can I slow down how fast my roof ages?
Yes. Keep gutters clear, make sure the attic is well ventilated, deal with moss early, and restore the shingles before they turn brittle.
