Calgary attic ventilation, in plain English.

Why ventilation matters more than the shingles

The single biggest difference between a Calgary roof that lasts 15 years and one that lasts 35 years is attic ventilation. Most Calgary homeowners think the shingle determines roof life. The shingle matters — but a Class 4 shingle on a poorly-ventilated attic still fails inside 20 years. A Class 3 shingle on a properly-vented attic can outlast it.

What proper Calgary attic ventilation looks like

The rule is simple and frequently violated: 1 square foot of net free area (NFA) per 300 square feet of attic floor, balanced between intake (soffit) and exhaust (ridge or vents).

Most Calgary attics fail this rule in one of three ways:

Failure 1 — Total NFA is too low. Builder put in the minimum and it’s aged. Common in 1970s–1990s Calgary builds.

Failure 2 — All exhaust, no intake. Standard scenario: the roof has plenty of can vents or a ridge vent but the soffits are blocked or were never properly perforated. Air can’t move because there’s nothing coming in.

Failure 3 — Intake blocked by insulation. When you blow in attic insulation, if you don’t install baffles at the eaves, the insulation packs into the soffit space and blocks the airflow. Looks fine from the outside. Doesn’t work.

The symptoms

You probably have a ventilation problem if:

• ·Ice dams form at the eaves in January (warm air leakage = melted snow refreezing at the cold eaves).
• ·Your upstairs is unbearably hot in summer despite AC (the attic above is at 60°C trapping heat).
• ·You can see frost on nail tips inside the attic in winter (warm humid air condensing on the cold nail tips).
• ·Mould on the underside of the roof deck (chronic humidity in the attic).
• ·Shingles are curling or cupping before year 15 (heat damage from below).

The fix

A Calgary attic ventilation upgrade is typically $850–$2,400 depending on what’s currently in place. The work usually involves:

• ·Continuous ridge vent (replacing scattered can vents)
• ·Continuous soffit intake (perforating where needed)
• ·Baffles at every truss bay to keep insulation out of the soffit space
• ·Sometimes: gable-end vent closures (gable vents short-circuit ridge ventilation)

This is one of the highest-ROI things you can do for a Calgary roof. It cuts cooling costs in summer, eliminates ice dams in winter, extends shingle life by 5–10 years, and prevents attic mould.

We do this work, but more importantly we diagnose it correctly so you’re not paying for a fix you don’t need. Free assessment.