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→Ventilation
If you plan to spend your time in hot humid climates, you should consider a solution that incorporates a dehumidifier.
Ventilation rates can be expressed in several ways:
Cubic feet per minute (CFM) or litres per second (L/s) of outside air brought into the boat
CFM per person: CFM/p
CFM per unit floor area: CFM/ft2
Air changes per hour (ACH)
Standards for ventilation differ, and have varied over time subject to lobbying, energy efficiency doctrines and the emergence of sick building syndrome. A reasonable yardstick is somewhere in the range of 0.5-1.25 ACH or, more precisely, 1.0 ACH translating to around 1.66 CFM per 100 cubic feet of cabin volume. You can double check this to ensure at least 15 CFM/p.
For example, assume a boat having 6,000 cubic feet of volume and berths for five people. Using 1.0 ACH this yields 99.6 CFM and 15 CFM/p yields 75 CFM.
Maximum air velocity in ventilation ducts and vents should not exceed 2.6-3.3 ft/s (0.8-1.0 m/s) to minimise noise and differentials in air pressure. Air ducts for combustion systems can run as high as 40-66 ft/s (12-20 m/s).
Let’s work a complete example. Assume a salon of 1280 cubic feet. At 1.0 ACH this requires 21.3 CFM:
CFM = Volume * ACH/60 minutes
The corresponding vent area with a velocity of 2 ft/s is:
Vent Area = CFM/(Velocity * 60 seconds)
= 21.3/120
= 0.18 sq ft
= 25.6 sq in
Close enough.
In this case, we could put a 5- x 5-in intake vent at one end of the salon and a vent of the same size at the other end with an exhaust fan driving 2 ft/s.
== Air Conditioning ==