Butane and damp: why a gas heater fills your home with water

Butane and damp: the heater that fills the house with water

A butane heater can turn a living room into a swimming pool. It is no exaggeration: in a home on the Cantabrian coast, real puddles appeared in every corner after switching on the gas heating. The cause is elementary physics, usually ignored when comparing tariffs: burning butane produces water vapour, and in an already saturated environment that vapour has nowhere to go. The result is condensation on cold walls, windows and corners.

The solution applied in that case was domestic and second-hand: an 80-euro dehumidifier which, according to the account, made the puddles disappear. The routine was split: electricity with time-of-use rates at night, butane with the dehumidifier running during the day. A mix that does not come cheap on the bill, but at least dries the air.

How much water a bottle puts into your home

The figure that frames the whole problem is the ratio between fuel and water produced. According to a calculation circulating in the discussion, a bottle produces about 20 litres of water for about 14 litres of butane. That is the core of the matter: heating with butane not only raises the temperature, it also adds moisture to the air. And the warmer the air, the more water it can hold, so the problem multiplies until that vapour finds a cold surface.

Hence the first recommendation: ventilate when it is coldest. The relative humidity of outdoor air can be extremely high first thing in the morning, but it contains far less water than the warm indoor air. Opening the windows wide with the cold outside removes vapour; opening them at midday, with mild temperatures, leaves it inside. It is counterintuitive and it works.

Dehumidifier or the dry mode of the air conditioner

The alternative proposed is using the air conditioner in dehumidifying mode, the water-drop symbol. Here the technical nuance matters. In a dedicated dehumidifier, air passes over the cold element, condenses the water and then crosses the warm element, so it comes out dry without cooling the room. In a split unit, the cold element is inside and the warm one outside: it does dry the air, but at the cost of cooling it. Running butane and dry mode at the same time means heating on one side and cooling on the other.

Consumption also separates the two devices. A domestic dehumidifier runs at around 200-400 W, while an extractor hood can reach 500 W with considerable noise. The comparison is no small matter in a home where the goal is to spend less than with natural gas.

It is not the region, it is the house

Some people live on the Cantabrian coast without these problems, and the argument that wins out is that altitude and orientation matter more than the map. On the coast humidity is high; in the mountains, the cold reduces the amount of water the air can carry. One flat may suffer condensation while the one next door does not. Other people's experience is of little use: the physics of each home rules.

With all this, the prediction is cautious: butane will remain a compromise solution for those without natural gas, but it will require a dehumidifier alongside it. Anyone who installs it without that extra may end up mopping the floor.