Climate-controlled storage: what actually needs it
Which belongings are hurt by heat, cold and damp in a storage unit, which are fine without climate control, and how to pack either way.
The BoxTrack team · · 5 min readThe storage place has two prices on the board. The regular 10x10 unit is one number; the climate-controlled one, down the hall inside the building, is noticeably more. You've got a garage's worth of furniture, eight boxes of books, your grandmother's photo albums and a piano. The person at the desk says "it depends what you're storing," which is true and not much help.
Most things you'd put in storage don't need climate control. A few things really do, and for those the cost of the cheaper unit is the thing itself. Here's how to tell them apart.
What climate control does, and doesn't do
A regular drive-up unit is a metal box. In summer it gets about as hot as a parked car, in winter about as cold as outside, and the humidity follows the weather. A climate-controlled unit is usually indoors, in a building that's heated and cooled to stay within a set range.
What varies from one facility to the next is whether "climate-controlled" also means humidity control. Some buildings only manage temperature. For paper, photos, wood and leather, humidity matters at least as much as heat, so ask the facility what range they keep the building in, for both temperature and humidity, and whether that holds year-round.
Why heat and damp hurt things
It isn't mainly the hot day or the cold night. It's the swings, and the damp.
The Library of Congress tells families to keep photographs out of attics, basements, spots along exterior walls and places near heating vents, because those are the spots where temperature and humidity change the most. It suggests keeping relative humidity steady, with swings of less than 5% in a day. The National Archives puts the limits for family papers and photos plainly: keep relative humidity below 65% to prevent mold, and keep things out of damp basements, garages and hot attics.
High humidity brings mold and warping. Very dry air makes wood shrink and crack. Going back and forth between the two, day after day in a metal unit, is what splits veneer and curls photos.
What needs climate control
Photos, negatives and slides. These are the most sensitive. The Library of Congress notes that color photographs and negatives last longest in cool storage, and the National Archives' guidance for family papers and photos is to keep them below 75°F, cooler if you can, because cooler temperatures slow chemical decay.
Important papers, books and documents. Birth certificates, letters, a book collection. The Smithsonian Institution Archives recommends 35°F to 65°F for paper collections, with relative humidity between 30% and 50%. A drive-up unit in July can be far outside that.
Wood furniture you care about. Antiques, veneered pieces and good solid-wood furniture move with humidity. A cheap bookshelf will be fine; the dining table you inherited may not be.
Musical instruments. Pianos, guitars, violins and other wood instruments are built to stay in a home's range of temperature and humidity.
Leather, fabrics and upholstery, especially for long stays. Damp brings mildew; heat dries leather out.
Electronics. Condensation is the risk when a cold device meets warm, humid air. If you're storing a TV or computer for a winter, a steadier unit is worth considering.
Artwork, for the same reasons as photos and paper.
What's usually fine without it
- garden tools, bikes, the lawn mower (drain the fuel first, and check the facility's rules on gas-powered equipment)
- metal and plastic patio furniture
- kitchen things: pots, pans, everyday dishes
- most clothes, packed clean and dry in plastic bins
- holiday decorations that aren't candles or anything that melts
- boxed household items for a short stay of a few weeks
Length of stay matters. Everyday furniture can sit through one mild spring in a regular unit. Over two summers and a winter, the same piece takes more of a beating.
How to pack either way
Keep things off the floor. Put pallets or a plastic sheet down first. If water ever gets in, the bottom boxes are the ones that get wet.
Use plastic bins for anything soft or paper, with lids that seal. Cardboard soaks up moisture.
Don't wrap furniture in plastic. It traps moisture against the wood. Use moving blankets or cotton sheets instead.
Leave a walkway and a gap at the walls, so air moves and you can reach the back. Our guide to organizing a storage unit has a layout that works.
Keep the most precious things at home if you can. A shoebox of photos or the folder of important papers takes up almost no space in a closet, and a closet in a heated home beats almost any storage unit.
Know what's in there
A storage unit is easy to fill and hard to remember. Six months later, the question isn't whether the photo albums survived, it's which box they're in and whether they're at the back behind the couch.
BoxTrack keeps that list for you. Each box gets a QR label, you snap a photo of what goes in, and the item list fills in by itself. You can mark which boxes hold the fragile or sensitive things, note which unit and which corner they're in, and search for "photo albums" from your phone before you drive over. See how it works for a storage unit. Your first box is free.
If you're storing between two homes rather than for the long haul, storing your things between homes covers the mover's warehouse option and what happens to liability.
A quick way to decide
Ask three questions about each thing:
- Would heat, cold or damp damage it? (Paper, photos, wood, leather, instruments, electronics: yes.)
- Is it going to be in there through a summer or a winter?
- Could you replace it?
If the answers are yes, yes and no, it goes in a climate-controlled unit or stays at home. Everything else can go in the regular unit with a pallet under it.
Sources
- Library of Congress, Care, handling and storage of photographs
- National Archives, Storing family archives
- Smithsonian Institution Archives, Environment