Attic rain is not a roof leak. Attic rain is frost that formed on the underside of your roof deck through a cold snap, then melted when the temperature climbed, and dripped through the ceiling. Calgary’s chinook cycle produces exactly the conditions for it: weeks below freezing, then a 15 degree swing in 24 hours.
Fixing it means changing the air, not the shingles. Here is what that work has actually cost.
What does exhaust ventilation on the roof cost?
| Work | Jobs billed | Median | Range | Years |
|---|---|---|---|---|
| Roof vents added or replaced | 18 | $105 | $20 to $500 | 2020 to 2024 |
| Air ventilator unit installed | 16 | $338 | $105 to $2,910 | 2021 to 2025 |
| Ventilation repair or readjustment | 6 | $325 | $175 to $1,500 | 2022 to 2024 |
| Ridge vent, continuous attic space | 1 | $900 | $900 | 2024 |
What does intake ventilation under the eave cost?
| Work | Jobs billed | Median | Range | Years |
|---|---|---|---|---|
| Aluminum soffit | 3 | $3,525 | $1,275 to $13,500 | 2023 to 2024 |
What do insulation and damage repairs cost?
| Work | Jobs billed | Median | Range | Years |
|---|---|---|---|---|
| Blown-in or added insulation | 3 | $6,412 | $1,299 to $7,088 | 2023 to 2024 |
| Condensation and attic rain leak repair | 1 | $2,775 | $2,775 | 2026 |
| Attic access and lighting for inspection | 1 | $175 | $175 | 2024 |
| Lower attic space report | 1 | $0 | no charge | 2023 |
49 separate priced jobs across the whole cluster, deduplicated so an estimate and its matching invoice count once. The overall median lands at $240, because most attic ventilation work is small, frequent and cheap.
Those are line items from our own invoices, drawn from 836 documents issued between August 2019 and August 2026.
The ventilation fix is the cheap one, and it is not close. Adding roof vents cost a median of $105 across 18 jobs. Air ventilator units ran a median of $338 across 16. The insulation fix runs $1,299 to $7,088, and a full soffit replacement to restore blocked intake reached $13,500 on the largest job.
Most Calgary attic rain cases resolve on the exhaust side for a few hundred dollars. The expensive cases are the ones where intake has been blocked for years and the insulation is already compromised.
Why do Calgary attics do this?
Three things have to line up, and in Calgary they line up every winter.
1. Warm moist air escapes from the house into the attic. Bathroom fans venting into the attic instead of outside, unsealed pot lights, an open attic hatch, plumbing stack penetrations, and gaps around the top plate all leak indoor humidity upward. A family of four puts several litres of water vapour into the air every day through showering, cooking and breathing.
2. The attic is cold enough to freeze it. In a properly vented attic, the attic temperature tracks the outdoor temperature closely. That is by design.
3. The attic cannot exhaust the moisture fast enough. Blocked soffit vents, too few roof vents, or insulation stuffed into the soffit baffles all stop the airflow that would carry humidity out before it condenses.
The frost accumulates through a cold stretch. Then a chinook arrives, the roof deck warms, and the frost melts all at once. That is when the ceiling stains appear, and that is why homeowners call it a leak.
A roof leak drips when it rains or when snow melts on the roof surface. Attic rain drips during a warm-up after a hard freeze, usually away from any penetration. If your ceiling stains show up during a chinook and not during rain, you have attic rain.
How do we tell attic rain from a roof leak?
| Signal | Attic rain | Roof leak |
|---|---|---|
| When it appears | During a warm-up after sustained cold | During or after rain, or during snowmelt |
| Where it appears | Scattered, often mid-ceiling or along exterior walls | Traced to a penetration: chimney, skylight, vent, valley |
| What the attic shows | Frost or water on the underside of the sheathing across a wide area | Staining following a single path down rafters or trusses |
| Insulation condition | Damp over a broad area, often near the eaves | Wet in a defined column |
| Nail heads | Frosted white across the deck | Normal |
We inspect for the difference before quoting anything. Inspections start at $175 and we have issued attic space reports at no charge.
Getting this wrong is expensive. Reflashing a skylight at $850 does nothing for a condensation problem, and adding insulation does nothing for a failed valley.
How do we fix it, in order?
1. Stop the moisture at the source
Cheapest and most effective. Confirm every bathroom and kitchen fan terminates outside the building, not into the attic. Seal the attic hatch. Seal around plumbing stacks and pot lights. Cut indoor humidity to roughly 30 to 40% in winter using the bathroom fans you already own.
This step costs very little and resolves a meaningful share of Calgary attic rain cases on its own.
2. Restore the ventilation
Roof vents: median $105 across 18 jobs. Air ventilator units: median $338 across 16 jobs. Ventilation repair and readjustment: median $325 across 6 jobs.
Calgary attics need continuous intake at the soffits and exhaust high on the roof. The most common failure we find is intake blockage, where blown insulation has drifted into the soffit and choked the airflow. Baffles restore it.
Where the attic runs continuously along a ridge, a ridge vent gives the most even exhaust. We installed one at $900 in September 2024. Individual roof vents and air ventilators do the same job in sections, and our invoices show them from $20 for a single extra vent during a re-roof up to $2,910 for an emergency ventilator installation with access difficulties.
Restoring blocked intake is the expensive half. Where soffit has to come off and go back on to reopen the airflow, we billed aluminum soffit at $1,275, $3,525 and $13,500 across three jobs. That is why we check intake before quoting exhaust: adding roof vents to an attic with blocked soffits pulls air from inside the house instead of from outside, which makes attic rain worse.
3. Correct the insulation
$1,299 to $7,088 in our records.
Insulation matters for attic rain in two ways that get confused. Adequate depth keeps the ceiling surface warm enough to limit condensation inside the living space. More importantly, insulation must not block the soffit intake. We have found attics with generous insulation depth and zero airflow, which makes attic rain worse rather than better.
Blown-in insulation across a full attic ran $6,412 in April 2024, with a broader insulation package at $7,088 in October 2023 and a smaller top-up at $1,299 in January 2023.
4. Repair the damage
$2,775 in January 2026 for a condensation and attic rain leak repair, covering the affected area and the resulting damage.
Will wet insulation in an attic dry out?
Lightly damp insulation in a properly ventilated attic dries out once airflow is restored and the humidity source is fixed.
Insulation that has been saturated repeatedly does not recover its function. Blown cellulose and fibreglass both lose thermal performance when compressed by moisture, and they stay compressed. Batt insulation that has been soaked and refrozen loses loft permanently.
The test is simple: if the insulation is matted flat, it has stopped working and needs replacing. If it is damp but still lofted, restore the ventilation and check it the following spring.
Wet insulation left in place also keeps the sheathing damp, which is how a ventilation problem turns into a decking problem. 193 of our 836 documents mention rotten wood, plywood, OSB or resheeting.
What are the signs of poor attic ventilation?
Check these before winter, not during it:
- Frost or ice on the underside of the roof sheathing, visible from the attic hatch on a cold day
- Frosted nail heads poking through the deck
- Damp or matted insulation, particularly near the eaves
- Ice dams at the eaves, a sign the attic is warmer than it should be
- Ceiling stains that appear during a chinook rather than during rain
- A bathroom fan you can hear but cannot find an exterior vent for
- Soffit vents blocked by insulation, visible from inside the attic
- Mould or dark staining on the sheathing
Any two of those together justify an inspection. We charge from $175 and have issued attic reports at no charge when they led into work.
What does this have to do with your roof?
Ventilation gets specified during a roof replacement, which is the cheapest moment to fix it. Every Fratello roof replacement includes new air vents, plumbing stack flashings, and bathroom, kitchen and dryer fan flashings as part of the standard scope.
If you are replacing your roof and you have had attic rain, say so before the quote. Adding vents during a re-roof costs a fraction of adding them afterward, exactly as it does with skylights.
For replacement pricing, see what a roof replacement costs in Calgary.
How did we produce these numbers?
We exported every estimate and invoice issued by Fratello Roofing & Exteriors Ltd from our Joist system and parsed 1,818 priced line items across 836 documents.
- Date range: 5 August 2019 to 18 August 2026
- Priced jobs in the ventilation and insulation cluster: 49, deduplicated so an estimate and its matching invoice count once
- Documents adding or replacing vents: 79
- Documents mentioning attic: 44
- Documents mentioning insulation: 30
- Documents mentioning soffit: 26
- Documents mentioning vapour barrier: 22
- Documents mentioning frost, ice buildup or condensation: 15
We will say plainly which numbers rest on a thin sample. Ridge vent, attic rain repair and blown-in insulation each carry a handful of jobs, and we have shown the individual prices rather than dressing them up as a range. Roof vents and air ventilators, the work that resolves most cases, rest on 34 jobs between them and those figures are solid.
No customer name, address or contact detail appears on this page.
Updated 19 August 2026.
Frequently asked questions
What are the signs of attic moisture?
Frost or ice on the underside of the roof sheathing, frosted nail heads, damp or matted insulation near the eaves, dark staining on the sheathing, ice dams forming at the eaves, and ceiling stains that appear during a chinook rather than during rain.
Why does my attic condense in cold weather?
Warm moist indoor air escapes into the attic through bathroom fans, unsealed pot lights and the attic hatch, then meets a roof deck sitting at outdoor temperature. Without enough soffit intake and roof exhaust to carry that moisture out, it freezes on the sheathing.
Is it normal to have condensation in the attic?
Light seasonal frost on the sheathing during extreme cold is common in Calgary. Frost thick enough to drip during a chinook, matted insulation, or staining on the sheathing all indicate the attic is not exhausting moisture fast enough and needs ventilation work.
How do I fix condensation in my attic?
In order: stop indoor moisture reaching the attic by venting bathroom fans outside and sealing the hatch and pot lights, restore soffit intake and roof exhaust, then correct insulation. Fratello billed roof vents at a median of $105 and blown-in insulation at $6,412.
How much does it cost to fix attic rain in Calgary?
The ventilation fix is the cheap one: roof vents at a median of $105 across 18 jobs, air ventilator units at a median of $338, a continuous ridge vent at $900. Insulation ran $1,299 to $7,088, and one full attic rain repair came to $2,775.
How do you tell the difference between a leak and condensation?
Timing and pattern. Attic rain drips during a warm-up after sustained cold and appears scattered across the ceiling. A roof leak appears during or after rain and traces to a specific penetration such as a chimney, skylight or valley.
How to tell if a roof is leaking into an attic?
Look for staining that follows a single path down a rafter or truss from one point, wet insulation in a defined column rather than spread widely, and water appearing during rain. Widespread frost across the sheathing points to condensation instead.
How do you dry out moisture in an attic?
Restore airflow first, since ventilation is what removes moisture from an attic. Remove saturated insulation, which holds water against the sheathing. Fix the indoor humidity source. Fans and dehumidifiers help temporarily but do not address why the moisture arrived.
Will wet insulation in an attic dry out?
Lightly damp insulation dries once airflow is restored and the moisture source is fixed. Insulation that has been saturated and matted flat has permanently lost its thermal performance and needs replacing. Matted flat is the test.
What are the signs of poor attic ventilation?
Frosted sheathing and nail heads, soffit vents blocked by drifted insulation, ice dams at the eaves, an attic noticeably warmer than outdoors in winter, matted insulation, and bathroom fans with no visible exterior termination point.
Can too much insulation in an attic cause condensation?
Insulation depth itself does not, but insulation that drifts into the soffits and blocks intake airflow absolutely does. Fratello has found attics with generous insulation depth and effectively zero ventilation, which makes attic rain worse rather than better. Baffles solve it.
Will mould in the attic make you sick?
Health effects from indoor mould vary by person and by exposure, and that assessment belongs to a physician or an indoor air quality professional, not a roofer. What we can tell you is that attic mould signals a moisture and ventilation problem, and removing the moisture source is what stops it returning.
Is there a way to check if my attic has moisture in it?
Open the attic hatch on a cold Calgary morning and look at the underside of the roof sheathing with a light. Frost across the deck, frosted nail heads or dark staining all confirm it. Fratello inspections start at $175.
Where these numbers come from
836 Fratello Roofing & Exteriors Ltd documents, 5 Aug 2019 to 18 Aug 2026. Prices are what Fratello Roofing & Exteriors Ltd actually quoted and invoiced, not an industry average. Last updated August 19, 2026.