23:46 10-12-2025

Cellar condensation solved: coals method and dehumidifiers

Generated by DALL·E

Learn why cellar condensation forms and how to fix it: ventilation, ceiling insulation, coals heating method, and dehumidifiers to control humidity and mold.

The cellar is still the go-to place for storing preserves and harvests, but keeping the right microclimate there isn’t always straightforward. Moisture, mold, and sharp temperature swings can quickly spoil supplies and damage the walls. One of the most common headaches is condensation that beads on the ceiling and trickles down the walls.

Locals have long learned how to deal with it and share simple yet reliable techniques.

Why condensation forms in a cellar

Water droplets on the walls come from temperature differences. When the ceiling is colder than the air inside, moisture in the air settles on the concrete slabs. There are many sources of humidity: vegetables, jars of pickles, wooden shelving.

The problem gets worse if the ceiling wasn’t insulated during construction or the cellar sits too low—closer to groundwater. Without ventilation, mold quickly takes over, damaging surfaces and whatever is stored inside.

Key causes:

• lack of ceiling insulation;
• weak or absent ventilation;
• poor wall waterproofing;
• faults in the drainage system.

How to tell humidity is high

A hygrometer shows the level precisely, but there are tried-and-true home tricks as well:

• Wooden splinters: if they bend after a day in the cellar, the air is damp.
• A cold bottle: condensation on the glass after a couple of hours signals excess moisture.
• A candle: in dry air the flame is lively; in damp air it’s steady and yellow.

These methods help spot the problem early, before it turns into puddles on the floor.

Old-school method: heating and airing with coals

This approach is used where there are no dehumidifiers or modern ventilation. It calls for caution, but delivers a quick effect.

What you’ll need:

• a metal bucket with small holes;
• charcoal for a fire or grill;
• a strong rope for hanging.

How it works:

• Light the coals until they hold a steady glow.
• Lower the bucket with coals into the cellar on the rope, about half a meter above the floor.
• Close the door and check periodically so the coals don’t go out.
• No one should enter while the coals are burning—the combustion products are dangerous.
• Hot air dries the walls and ceiling, and the smoke helps suppress mold. After treatment, keep the cellar closed for two more days, then air it out and return the supplies.

Modern solution: a household dehumidifier

A dehumidifier works gently and is suitable for regular use. Before switching it on, prepare the space:

• clear the cellar of stored goods;
• wash surfaces with a soapy solution;
• treat mold traces with copper sulfate;
• let the walls dry.

After that, run the dehumidifier for 2–3 days. In tougher conditions, use it regularly to prevent moisture from returning.

How to keep the cellar dry

Several conditions matter for a stable microclimate:

• working ventilation;
• ceiling insulation;
• quality waterproofing;
• no cracks in the walls;
• proper placement of the cellar relative to groundwater.

In plastic cellars, condensation most often appears because of weak ventilation or an uninsulated lid. Remove those factors, and the space quickly becomes dry and suitable for storage.