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Humidity inside a boat is as pleasant as a bucket full of sand spread on the sleeping bag you are sleeping in. And yet it is not just a matter of comfort: the much-feared condensate that forms in winter months when the temperature drops and the boat is moored for weeks or even months hundreds of kilometres far from home, if not reduced and possibly eliminated, may turn into a nightmare for pleasure boaters and be the cause of economic damage and poor liveability.

Condensate, as a matter of fact, is harmless in itself and is wiped away with a cloth. Problems arise as persistent condensate usually causes mould to grow. This damages surfaces in cabins and dinette, soaks mattresses and tissues acquire an awful (and unhealthy) green colour difficult to be removed. Wood exposed to moisture is vulnerable to decay while electrical systems and cable connections are at risk of oxidation, etc. etc. Moreover, also the adverse effects on health have to be taken into account. 

In short, moisture and humidity below deck must be fought with all means available. And, luckily, there are many and for every budget. Of course, having not a single speck of condensate in your boat in the wintry months in Northern Italy is a privilege for the few, whereas reducing humidity inside a boat to acceptable levels is at hand to every pleasure boater. It should be mentioned that high-quality boat building and proper insulation make the difference. Properly built and well insulated boats, no matter if tens of years old, may be drier in winter than more modern boats under the same weather conditions.

First of all, we all should keep in mind that sometimes all it takes are small gestures to produce significant results. Air the boat as often as possible, especially during a sunny day. Let fresh air circulate inside the boat as this is the best method of avoiding condensation. If unfortunately you cannot do this, take some tips before leaving your boat. Remove the mattresses or, at least, position them vertically, open the peaks the let the air circulate below deck. Make sure no water leakage comes from portholes, companion ways, etc. and the bilge is perfectly dry. Once all this has been done, let’s talk about preventive measures.

There are mainly three ways to fight humidity: air circulation, moisture absorbers and electric dehumidifiers. It goes without saying that, should you, unlike most of pleasure boaters, spend long periods on your boat also in winter, this will help to prevent condensate formation. However, prevent and not eliminate, as in winter even our well-heated houses may suffer from condensation. As far as boats are concerned, in the vast majority of cases electric heaters and oil radiators cannot be turned ON below deck all day long both for safety and cost reasons.

Among air-based options, a wind scoop like the Wind scoop for hatches ( is very simple and practical. It is installed at bow and very effective in channeling fresh air below deck. Of course, it cannot be left open in case of spells of harsh weather that are quite common in winter months even in the Mediterranean. Fans are a different option. Both 12V fans and solar fans are available. While the former are electrical devices whose prolonged use is not recommended for the reasons mentioned above, the latter ensure continuous operation without being connected to the on-board system. As an example, this model of Solarvent automatic solar vent (, when properly solar-powered, provides 30 hours of continuous operation.

Now let’s say a word about dehydrating moisture absorber. They are salt or silica gel-based, refillable, user friendly and cheap. No connection to the electrical system is required. Very effective in drawing water from the air, which is collected in a dedicated tray. This is one of the many models available on the market: ABSODRY® moisture absorber ( They can be positioned even in confined spaces, and, of course, the more you place the better. While salt crystals need to be refilled, silica-gel can be restored to its original state by heating it in a microwave oven.  

Better performances are guaranteed by electric dehumidifiers. This is a totally different option. Powerful and reliable, they clean the air below deck and drastically reduce condensate formation. They are provided with switching sensors for detecting the set moisture threshold (note that the risk of mould formation is very high when moisture exceeds 60%). Among the cons there are the cost, much higher than a moisture absorber, the dimensions and above all the fact that they require electrical supply.

Now the choice is up to you.

Osculati Srl
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