Last Updated on October 26, 2026 by Umar Farooq
How to store a sleeping bag without mildew: get it completely dry, take it out of the stuff sack, and keep it loose in a large breathable bag somewhere cool and dry indoors. Nearly every mouldy sleeping bag was put away slightly damp and squashed small.
I have been that person who got home from a wet weekend, shoved the bag back into its sack “to deal with later”, and found it three weeks later with a smell like a damp tent had died in it. The bag was fine. The sack was a very small, very warm, very damp box.
Why do sleeping bags get mildew in the first place?
A sleeping bag collects moisture from three places: condensation in the tent, rain that got in somewhere, and you (people give off moisture all night). Add insulation and fabric, and any damp trapped in a closed sack has nowhere to go. Mould needs moisture, something to feed on, and still air, and a bag squashed into a sack supplies all three.
Nemo’s care guide says plainly that making sure the bag is completely dry before storage is the most effective way to prevent mould and mildew (Nemo Equipment, cleaning, repairing and storing your sleeping bag). A bag that feels dry on the outside can still hold damp deep in the fill.
How to store a sleeping bag without mildew: six steps
1. Air it the day you get home. Unzip it fully, turn it inside out if the lining is damp, and hang it or lay it out until it is properly dry. Great Walks advises doing this after every trip, and checking the hood, footbox and shoulders, the places that hold the most moisture.
2. Give it longer than you think. If you have washed it, Nemo suggests air drying for at least 24 hours in low-humidity conditions, then shaking it to restore loft. In a damp British house, a day on a clothes horse in a heated room beats a day in the shed. See how to dry bedding indoors for the drying part.
3. Do not store it in the stuff sack. Long-term compression flattens the insulation and keeps the bag from breathing. The stuff sack is transport.
4. Use a large, breathable storage sack. Cotton or mesh, or a hanger, which Nemo also mentions. A clean pillowcase will do in an emergency. Both Nemo and Great Walks recommend an oversized breathable sack or hanger for long-term storage.
5. Pick a cool, dry, dark room. Not the cellar, not the garage and not the loft: damp basements and hot attics are the places guides repeatedly warn against. A shelf in a bedroom wardrobe is better than any of them.
6. Skip airtight bins. One guide warns that sealed containers trap condensation. A plastic tub with a lid is fine for a bag that is genuinely dry, in a room that is dry, but I would still choose breathable, because “genuinely dry” is easy to get wrong.
Does the storage room’s humidity matter?
Yes, and it is the part most guides skip. A bag in a breathable sack still takes on moisture from the room if the room is humid. The EPA recommends keeping indoor relative humidity below 60%, ideally 30 to 50% (EPA, brief guide to mold, moisture and your home). A cheap hygrometer on the shelf tells you where the cupboard sits, and if it is high, what humidity mould grows at explains what to aim for.
A moisture absorber near a stored bag can help in a small cupboard, but it is a backup. It will not dry a damp bag, and do moisture absorbers work explains where they fall short. If the whole cupboard is the problem, the storage unit guide covers why closed spaces hold damp.
What if the bag already smells musty?
Air it somewhere dry and breezy for a day or two, and sniff again. A light mustiness often fades once the fill is properly dry. If it persists, wash it following the care label: Great Walks advises avoiding fabric softener and bleach, which can damage the fabric and insulation, and drying thoroughly afterwards, which can take several hours in a large dryer on low heat with clean tennis balls.
If you can see mould, do not shake the bag indoors. Take it outside, wear a mask and gloves, and keep it away from clean items. If you have health concerns about mould, ask a doctor. Heavily mouldy fill may not be recoverable, and a down bag that has stayed wet can clump.
Dry first, loose second, and a sleeping bag keeps for years
The whole job is boring and short: dry it completely, take it out of the stuff sack, give it a breathable home in a dry room, and check the cupboard’s humidity now and then. Do that and the bag you pack for next summer will smell of nothing at all, which is the correct smell.
FAQ
Can you store a sleeping bag in a compression sack?
Only briefly, for transport, and only when completely dry. Long-term compression flattens the insulation, and a tight sack gives moisture nowhere to go.
Should a sleeping bag be hung or stored flat?
Either works. Some guides suggest hanging, others laying it loosely in a large sack. What matters is that it is not squashed and that air can reach it.
Where is the best place to store a sleeping bag?
A cool, dry, dark place indoors, such as a wardrobe shelf. Damp cellars and hot lofts are the usual culprits for mildew.
How do I know my sleeping bag is dry enough to store?
Check the thick parts: the hood, footbox and shoulders. If any section feels cool or clammy, or the fill is clumped, keep drying. When in doubt, give it another day.
Is it okay to put a sleeping bag in a plastic bin?
It is okay if the bag is fully dry and the room is dry, but a sealed bin traps condensation if there is any moisture. A breathable sack is the safer choice.
