--- title: "Wine Cellar Humidity Too High or Mold: Causes and Fixes" description: "Wine cellar mold starts as a musty smell, then white or green fuzz on the rack posts, spotted labels and dark specks in the corners, usually with a hygrometer…" url: "https://winecellarrepair.center/problems/cellar-humidity-too-high-or-mold/" --- # Wine Cellar Humidity Too High or Mold Wine cellar mold starts as a musty smell, then white or green fuzz on the rack posts, spotted labels and dark specks in the corners, usually with a hygrometer reading well above 70 %. ## What it usually means. A cellar is kept between roughly 50 and 70 % relative humidity. Above that, the wood of the racks, the labels and the drywall become food for mold. Most of the moisture comes from outside the room: warm humid air seeping through a wall or ceiling with no vapor barrier, a door without a seal, or a slab that wicks ground water. The cooling unit is supposed to take some of it out, but a unit that is oversized cools the room so fast that it shuts off before it has dried the air, and one whose drain backs up can pour water right back in. Poor air movement leaves still, damp corners even when the average reading is fine. The fix is often in the room as much as in the machine, and mold on the structure should be cleaned properly, not just wiped from the bottles. The 5 causes, cheapest first Answer these first 01 What does a hygrometer on a middle rack read, and is it worse in summer? 02 Where does the mold grow: on rack posts, on the walls, on labels, or around the unit's grille? 03 Was the cellar built with a vapor barrier on the warm side of the insulation, and is there any glass wall? 04 Does the unit run in short bursts and switch off, or run long cycles? 05 Is there any sign of water from the unit's drain or from the slab? ## Check these before you book. Wine cellar mold: 5 checks, and none of them costs anything. 01 Read a hygrometer on a middle rack for a few days and note the highest figure. 02 Photograph where the mold grows, so we can see whether it follows a wall, a corner or the unit's air path. 03 Check the unit's drain for water pooling on the cellar side. ### Also worth checking - Move bottles with valuable labels away from the dampest wall for now. - Tell us the make, the model number and, if you know it, how the cellar walls were built. ### How soon does it need a visit? Not an emergency, but it will not fix itself. Book within a week or two, and sooner if mold is spreading on the structure rather than on a few labels. ## The causes, cheapest first. 5 things wine cellar humidity too high or mold turns out to be, from condensate backing up into the room to oversized unit short-cycling. [The cost guide](https://winecellarrepair.center/cost/) 1. 01 low ### Condensate backing up into the room A blocked tray or line spills the water the unit collected back into the cellar, feeding the damp it was meant to remove. [Fixed by cellar condensate drain and pump repair](https://winecellarrepair.center/services/cellar-condensate-drain-and-pump-repair/) [See cellar cooling unit leaking water](https://winecellarrepair.center/problems/cellar-unit-leaking-water/) 2. 02 low to moderate ### Humidity control set too high or stuck On systems with humidity control, a humidifier that will not stop or a humidity sensor reading low keeps adding water the room does not need. [Fixed by cellar humidity control repair](https://winecellarrepair.center/services/cellar-humidity-control-repair/) 3. 03 low to moderate ### Still air in corners A slow cellar-side fan, or racking that blocks the unit's supply, leaves pockets of damp still air where mold starts first. [Fixed by cellar evaporator and condenser fan repair](https://winecellarrepair.center/services/cellar-evaporator-and-condenser-fan-repair/) 4. 04 varies ### Missing or broken vapor barrier Without a continuous barrier on the warm side of the walls and ceiling, humid air migrates into the cold room and condenses in the insulation and on the surfaces. It is the most common root cause and is found with a room check. [Fixed by cellar cooling load and room check](https://winecellarrepair.center/services/cellar-cooling-load-and-room-check/) 5. 05 varies ### Oversized unit short-cycling A unit much larger than the room needs reaches the set point in minutes and stops before it has pulled much water out. The room stays cold and damp. [Fixed by cellar cooling load and room check](https://winecellarrepair.center/services/cellar-cooling-load-and-room-check/) [See cellar cooling unit short cycling](https://winecellarrepair.center/problems/cellar-unit-short-cycling/) 6. What it costs ### Every repair on the site's cost scale, side by side Open the cost guide ## What else it could be. Most often confused with condensation on wine cellar walls or glass, then cellar cooling unit short cycling. [All problems](https://winecellarrepair.center/problems/) Codes that come with it - [`EA` CellarCool · Humidity](https://winecellarrepair.center/error-codes/cellarcool-ea/) - [`!2` Wine Guardian · Humidity](https://winecellarrepair.center/error-codes/wine-guardian-alarm-2/) - [`Flashing humidity with (!)` Wine Guardian · Humidity](https://winecellarrepair.center/error-codes/wine-guardian-high-humidity-alarm/) Also related - [**Wine Cellar Humidity Too Low** 4 causes](https://winecellarrepair.center/problems/cellar-humidity-too-low/) ### Condensation on Wine Cellar Walls or Glass 5 causes ### Cellar Cooling Unit Short Cycling 5 causes The collection is exposed ### Cellar Cooling Unit Leaking Water 6 causes ## The makes it happens on. 7 makes on this site; wine cellar humidity too high or mold can show up on any of them. Each mark opens that make's own page. [All 7 brands](https://winecellarrepair.center/brands/) ## Wine Cellar Humidity Too High or Mold, where we come out. 9 metros, each with its own page. 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Not the wine inside a sound cork and capsule. It does spoil labels, which matters for collectible bottles, and mold on racks and drywall keeps spreading until the moisture behind it is fixed. ### Why is my cellar damp when the cooling unit is new and large? A unit much larger than the room cools it in short bursts and shuts off before it pulls much water from the air. Right-sizing matters for humidity as well as temperature. ### Can I run a dehumidifier in the wine cellar? A small one can help as a stopgap, but it adds heat the cooling unit then has to remove, and it treats the symptom. Find where the moisture enters first. ### How do you find a gap in a cellar's vapor barrier? We look for cold, damp patches on walls and ceilings, check around outlets, lights and wiring holes, measure surface temperatures, and compare humidity inside and outside the room. Gaps often sit where trades cut through the wall after it was sealed. --- **[Read on the site: Wine Cellar Humidity Too High or Mold: Causes and Fixes](https://winecellarrepair.center/problems/cellar-humidity-too-high-or-mold/)** **[Book a visit with WineCellarRepair.center](https://winecellarrepair.center/schedule/)**