Ventilation on a Liveaboard Boat

Ventilation of your boat's interior is important to keep you and your crew comfortable and healthy.

Moisture, humidity  and condensation below decks can promote the growth of mildew and negatively affect your health.

It will also create an environment that eats up your upholstery and causes your electronic equipment to fizzle and die.

Moisture inside your boat's hull can even contribute to dreaded osmotic blistering if your hull or cabin stop gets saturated with moisture.  Blistering can be a very expensive problem to repair.

Ventilation Can Be Active Or Passive

Even before you consider air conditioning on your boat, you need to make sure you have a good system for moving the inside air.  Vents can be described as either passive or active.

Passive vents include ports and hatches that can be opened along with cowl vents and louvers or grills.  Some of these louvers or grills can be on the companionway hatch or on various stowage compartment doors in the boat.  These passive vents are okay if your boat is in a constantly windy environment or if the boat is always on the move.

In Florida and other hot humid places, passive vents are not usually enough to keep the boat well ventilated.  You have to consider adding some active ventilation to keep the air moving.

Active ventilators usually incorporate a fan to keep the air moving.  Self contained batteries, solar energy or the boat's batteries are used to provide power to the fan.  Some of these vents include both intake and exhaust fans to increase your chances of moving the air.

Your system has to be designed to keep water from waves and rain from getting into your nice dry boat.  The dorade box pictured above is a good way to keep water from getting into your boat through a cowl vent.  The box is designed to keep water from entering into the boat and letting it drain out holes on the low side of the box.

Boat designers also recommended that your system be able to change the air in the boat completely every hour.  This means your design has to allow intake of new air to replace the old air that's exhausted.

There are many online sources that will give you ideas for designing your liveaboard system.  One of the best is West Marine.  They have experts on every aspect of boat design and maintenance.

Even if you get the system designed and installed properly, you will find yourself wanting air conditioning as the weather gets warmer and more humid.  Biting insects like gnats and mosquitoes who enter your boat through your vents, ports and hatches and will convince you to go with air condtioning.

You will learn more about air conditioning in the next section of this website.


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