Why Your Windows Fog Up—And Why It Matters
Condensation isn’t just an annoyance. Droplets sitting on sills invite mold, warp wooden blinds, rot plaster, and spike respiratory problems. The United States Environmental Protection Agency (EPA) warns that“indoor relative humidity above 60 % accelerates dust-mite growth and mold spore release.” In winter, single-pane or poorly sealed windows routinely hit 80 % humidity at sunrise—ripe for the drip.
Electric dehumidifiers work, but they cost $150–$300 and add $10–$30 a month to your electric bill. If you rent or own a studio, you can slash humidity for the price of a_stamp.
The Only Two Ingredients You Need
1. Plain, non-iodized table salt: $.79 for a 26 oz carton.
2. Unscented clay cat litter: $4.50 for 25 lbs—one jug will treat three average rooms.
Both are hygroscopic: chemists call them “desiccants,” substances that grab water from the air and lock it inside themselves.
The 3-Minute Assembly
What you’ll use:
- 1 pair of clean, sheer knee-high hose (spares or dollar-store ones)
- ½ cup salt
- ½ cup clay litter
- scissors and a twist-tie or rubber band
Steps:
1. Cut each stocking leg into two 8-inch tubes.
2. Spoon salt into one section, litter into another.
3. Knot the open end; double the knot. You now have two refillable moisture pouches.
4. Hang the salt pouch on the window latch (it sits right in the airflow gap that’s so humid). Place the cat-litter pouch flat on the sill. Gravity and surface area do the rest.
How Long Before You Feel the Change
Expect to see the salt turn slushy in 6–12 hours, litter darken within 8–24 hours, and fog on interior glass disappear overnight in a small room (under 120 sq ft). Test with a $10 digital hygrometer; drops of 20 %+ are common. Swap both packs every 48 hours, or whenever the salt clumps rock-solid. Dehydrate spent salt in a low oven (200 °F for 15 min) and the mix is good to go again.
Scaling Up: Multi-Room Game Plan
Large living room? Lay four litter pouches along the base of leakiest windows. Treat entryways, kitchens (behind the curtains) and the bathroom after showering. A single 25-lb jug of clay litter will recharge the whole house two to three times a month.
When the Homemade Dehumidifier Isn’t Enough
If the humidity stays north of 55 % even after 72 hours, check for external causes: leaking sill caulking, dryer hose into a living room (yes, it happens), or indoor clothes-drying racks. Seal gaps with silicone caulk, vent the dryer to the exterior, or dry clothes in the bathroom with the exhaust fan running.
DIY Warning and Safety Tips
Never add scented litter—odor oils can off-gas in enclosed spaces. Don’t use rock salt; the chunks are messier and can scratch glass or finish. Keep pouches away from kids and pets; both salt and litter are harmless in small doses, but a stomach full of either is a vet bill.
Money-Saving Alternatives to Test
- Rice: Surprisingly effective but slower. Swap every three days.
- Charcoal briquettes: Great odor control; reduce RH about 8 % in 8 l cages.
- Chalk: Cheap for drawers—slide a few sticks into old socks.
Cleaning the Stains Left Behind
Once windows stop sweating, wipe sills with a 1:1 vinegar-water solution and a microfiber cloth. For stubborn mold lines, dab 3 % hydrogen peroxide, let sit 10 minutes, rinse, dry. Repaint with anti-mildew primer if stains have eaten the lacquer.
FAQ
Does coarse sea salt work better than table salt?
No. Granule size changes speed, not capacity. Stick to the cheap stuff.
What if I don’t have cat litter?
Pure calcium chloride ice-melt will work, but it’s more corrosive. Use small cups instead of pouches to avoid contact with finishes.
Can I make these pouches ahead?
Yes, but store them in airtight Tupperware to stop pre-soaking on humid days.
Wrapping Up
Punching holes in your paycheck isn’t the only way to fight damp air. A salt-cat-litter duo costs less than a loaf of bread and beats prime-month window fog before sunrise. Try it tonight; the morning view will be crystal clear—and your wallet won’t sweat.
Sources
- EPA – Moisture Control in Buildings
- Applied Mechanical and Materials – Hygroscopic Desiccants Comparison
- ENERGY STAR – Average Dehumidifier Operating Cost
This article is for informational purposes only and should not substitute professional indoor-air or medical guidance.