Marine Outfitters
VENOM = Clean Waterline !
Save on Shipping
Currency: Canadian Pricing American Pricing
Categories > Ventilation



Proper ventilation is important for the maintenance of your boat, and is a necessity for the comfort of you and your crew.

A good ventilation system will:

  • Reduce moisture and humidity belowdecks when the boat is left unattended.
  • Reduce the chances of mold, mildew and musty air development caused by trapped moisture and humidity in the boat.
  • Help electronics and fabrics last longer by maintaining a drier climate.
  • Reduce the likelihood of blisters caused by moist air saturation of the hull.
  • Active and Passive Ventilation
  • Vents fall into two basic categories: passive or active.
    • Passive ventilators, such as cowl vents, clamshell vents, louvers, grilles, ventilating sails, ports and hatches simply provide an access path for air to enter or leave the interior of the boat. As long as either the boat or the air itself are moving, they work just fine. Of course on those hot, still days when the only things moving are the mosquitoes, they’re not much help.
    • Active ventilators, such as Nicro’s Powervent 3000, Day/Night Plus Solar Vents and Stainless 12 Volt Vents all incorporate a fan to keep air moving even when the boat or breeze is still. Solar energy or ship’s power is used to power the fan depending on the ventilator. These vents come with both intake and exhaust fan blades for flexibility in creating your ventilation system.

Designing a ventilation system that works
A properly designed ventilation system provides adequate air circulation throughout the boat without allowing water from waves, spray or rain to come aboard. Experts recommend that your ventilation system should provide at least one air change every hour. This means provisions must be made for both the intake of new air and the exhaust of old air. Set up your system to provide a “crossflow” of intake and exhaust ventilation wherever possible. If you only add one active ventilator, use it for exhaust.

A typical 30-footer has about 800cu.ft. of belowdecks interior volume. Unfortunately, this space is often broken up into distinct cabins or compartments that may restrict the free movement of air throughout the boat. Therefore, simply installing a pair of vents rated for 800cu.ft. per hour of airflow may not be adequate to get the total ventilating job done.

Each cabin and head should have some kind of ventilation, especially if the space can be closed off from the rest of the boat. Louvered doors, or vent grilles in solid doors help air circulate into lockers, forepeaks and other isolated areas of the boat.

During wet or rough weather, you’ll need to be able to shut off or remove vents to prevent water from finding its way below. Racing boats may need to use vents that can be removed while the boat is in use in order to keep the decks free of possible snags.