Snow in the attic: why it blows in and what to do about it
A dusting of snow on the insulation looks alarming. Most of the time it is wind-driven powder that found a vent, and the real problem is the melt water.
Snow inside the attic is almost always wind-driven powder that came through a vent, not through a hole in the roof. Dry, fine snow behaves like a gas in a strong wind. It slips through soffit vents, gable louvers, ridge vents and any gap around a vent cap, then settles on the insulation. The giveaway is the pattern: a fine, even dusting near the openings, and none under solid roof deck.
How to tell blown snow from a real leak
Look from the hatch with a flashlight, and stay on the hatch frame or a board you trust. Do not step between the joists. Blown snow sits in drifts or a thin film close to a vent, and it is dry to the touch until it melts. A roof leak leaves a stain on the sheathing and a dark track on the rafters, and it shows up with the thaw, not during the storm.
If you cannot tell, our find the leak tool asks the timing questions that separate the two. Stay off the roof. Everything you need is visible from the attic floor or the ground.
The problem is the melt, not the snow
Snow on insulation is harmless while it stays frozen. The trouble starts when the attic warms. Melt water soaks the insulation, which then loses most of its value and holds damp against the framing. That is the same chain of events described in our guide to wet attic insulation. A small drift is a ten minute job. A wide soaked patch can run on for weeks.
What to do from the floor
Scoop loose snow into a bucket or dustpan before it melts, working from the hatch edge. If the drift is too far to reach safely, leave it and let it melt, then check the insulation underneath. Lay down plastic sheeting and a towel under any dripping spot. Run a fan on the damp area once the storm passes, if you have safe access.
Do not climb up to seal or cover the vents in a storm. A snow-covered roof is slick, and the wind that blew the snow in is the same wind that can knock you off. Wait for dry weather and call a roofer if a vent cap is cracked or missing.
Why it keeps happening
A repeat problem usually points to the vents themselves. Soffit vents without baffles let the wind drive snow straight across the insulation. A ridge vent with a damaged cap lets powder fall in from above. Old gable louvers with a loose screen are a classic entry point. Fixing it often means adding baffles or a snow-resistant vent cap, which is a roofer or insulation contractor job.
Keep the airflow in mind while you do. The vents are there for a reason, and covering them to stop snow trades one problem for an attic ventilation problem and a damp attic later. Ask the contractor to keep intake and exhaust balanced.
When to call someone
Call a pro if the snow keeps returning after every storm, if insulation stays wet after the thaw, or if you see staining on the sheathing. A wet attic is also where attic mold starts, so do not leave damp insulation in place for long.
Frequently asked questions
Why is there snow in my attic?
Fine powder snow gets driven by wind through soffit vents, gable louvers or ridge vents. It is usually not a sign of a hole in the roof.
Is snow in the attic a roof leak?
Usually not. Blown snow sits near vents and is dry until it melts. A leak leaves stains on the sheathing and appears with the thaw.
Should I remove snow from my attic?
Yes if you can reach it safely from the hatch. Scoop it before it melts so it does not soak the insulation.
Can I cover my attic vents to keep snow out?
No. Blocking the vents upsets airflow and can cause condensation. Ask a contractor about baffles or snow-resistant vent caps instead.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- US EPA. A Brief Guide to Mold, Moisture and Your Home
- US EPA. Mold Cleanup in Your Home
- US EPA. Introduction to Indoor Air Quality