Calculate how much water your wood stove evaporates and its impact on indoor relative humidity. Maintain healthy winter air quality with ease. Proper humidification prevents dry skin, respiratory issues, and static electricity shocks common in wood-heated homes.
Enter the wood you burn per day, its moisture content, the room volume, and the ventilation rate in air changes per hour. The calculator estimates the water available for evaporation from your daily fuel at 95% recovery: burning 10 kg of wood at 20% moisture corresponds to 10 × 0.20 × 0.95 = 1.9 kg of water per day.
That vapor is spread across the room volume hour by hour and converted to relative humidity against the saturation density of 20°C air, which holds 17.3 g of water per cubic metre. Ventilation dilutes the gain: the rise is divided by the air-change rate whenever it exceeds one change per hour. For the 10 kg example in a 100 m³ room, the modeled rise is about 4.6% RH.
Two further outputs frame the answer. The recommended load estimates the daily wood quantity whose moisture release works out to roughly 3 g of water per cubic metre of room volume — about 1.43 kg for a 100 m³ room burning 20% moisture fuel. And whenever the raw model predicts more than a 50% RH rise, the result is capped there and flagged, because gains of that size point toward condensation rather than comfortable air.
A stove does not remove water from the room; it raises the temperature, and warmer air can hold far more moisture, so the same absolute water content reads as a much lower relative humidity. The calculator quantifies the counter-move, evaporating water back into the space, using the 17.3 g/m³ saturation density of 20°C air as the yardstick for each percentage point of RH.
Every air change replaces moistened indoor air with drier outdoor air, so the model divides the raw humidity rise by the air-change rate once it exceeds 1.0. A leaky space at 2 air changes per hour keeps only half the gain a tight one retains; below one change per hour no penalty is applied, because the divisor is floored at 1 so low ventilation can never artificially inflate the result.
If the inputs imply a relative-humidity rise above 50 percentage points, the calculator clamps the display at 50% and raises a flag instead of reporting the raw figure. Pushing indoor humidity that hard invites condensation on windows and cold exterior walls, and persistent condensation is the precursor to mold and structural moisture damage. The flag marks the configuration itself as the problem — typically too much wet wood for too small or too poorly ventilated a room.