Boat Condensation

[Faoilean]

Hello,

I have recently purchased a 1950 wooden Nordic Folkboat that appears to gather a considerable amount of condensation on the inside of the cabin over night.

The weather in Ontario this summer has been quite warm and humid. (no complaints!)

There are slats in the top companionway board, and a directional vent on the bow for circulation.

Can anyone tell me if this is a common problem on hot humid days with a wooden boat, or should I be looking for other ways of getting the air circulating within?

Thank you!

[Stu Jackson]

Condensation is an issue due to lack of ventilation, regardless of wood or fiberglass.

Boat & Marine Ventilation System | Marinco

[a64pilot]

Usually condensation is more of an issue in winter, but if AC power is available I'd look at some form of air conditioning. Mold is a real bear if it gets a start

[LakeSuperior]

Condensation occurs when the temperature of the inside surface of the hull/ribs are lower than the dew point of cabin air. Conductive heat transfer from the sea/lake keeps the inside surfaces cool and so condensation just keeps on happening if outside air is circulating through the cabin.

If you glue insulation to the inside of the hull then then a temperature gradient is formed. The heat transfer from the cool water is reduced so that the surface of the insulation is inherently warmer. Now there are fewer conditions for condensation to occur.

So when the outside ambient air is warm and moist close up the boat and minimize ventilation. Therefore, minimal condensation will occur. When the ambient air is cool and dry ventilate the cabin and dry things out.


The worst conditions for condensation are in the spring when the water is coldest, at least in the Great Lakes.

[Faoilean]

Thank you everyone, for taking the time to help address my issue!
Now I have a much better understanding, of what is actually taking place!
Unfortunately it's difficult to seal the cabin air in a Folkboat that is designed to be well ventilated to prevent rot.
Perhaps a possible remedy available to me is to find a way to keep the air moving throughout the cabin, during the hot humid days when the water temperature is having a cooling affect on the hull.
Much appreciated!

[LakeSuperior]

Originally Posted by Faoilean

Thank you everyone, for taking the time to help address my issue!
Now I have a much better understanding, of what is actually taking place!
Unfortunately it's difficult to seal the cabin air in a Folkboat that is designed to be well ventilated to prevent rot.
Perhaps a possible remedy available to me is to find a way to keep the air moving throughout the cabin, during the hot humid days when the water temperature is having a cooling affect on the hull.
Much appreciated!

Please read my post more carefully, I think you got it reversed.

[Faoilean]

After reading the information you provided, and not being able to seal the dry air within the cabin, I thought that possibly by using a fan and accelerating the air, it might cool it enough to prevent the moisture from forming on the inside of the cabin.

[LakeSuperior]

Originally Posted by Faoilean

After reading the information you provided, and not being able to seal the dry air within the cabin, I thought that possibly by using a fan and accelerating the air, it might cool it enough to prevent the moisture from forming on the inside of the cabin.

If the hull temperature is at or below the dew point of the air a fan will increase the amount of moisture formed. If the hull is warmer than the dew point a fan will help dry things out.

[Faoilean]

It doesn't look like there is an easy solution, as I can't very well insulate to bring up the hull temperature.
I'm hoping that as the days begin to cool, there won't be such a temperature difference and the air will become dryer.
Thank you for all the info!

[Lepke]

Condensation comes from several sources. Not only temp differences, but cooking, your breath, bilge evaporation, etc. Sleeping in an enclosed space can produce noticeable moisture.
I also have a wood hull. I have a vented hood over the stove and power vented bilge areas. This hull has 5 WT bulkheads, so each bilge has a plastic pipe the length of the bilge with holes every foot and plumbed/power vented outside the hull at about 50-100 cubic feet an hour. My bilge is closed so the air into the bilge is drawn near the overhead and down the sides between the ribs and across the bilge into the vent pipe. It keeps everything dry, no rot, no mold. My clothes smell like land clothes. Also, it keeps the floors a little warmer in winter. And I get no noticeable moisture on the surfaces or windows/ports. Also all my cabinets have small 12v square, computer type, fans venting into whatever cabin space.

[bcboomer]

Lepke
As I understand it you are drawing warm air from high in the cabin and down the hull. Do you get a lot of condensation on the hull surface? Where does the make-up air come from?

[Faoilean]

Thank you everyone for the great info! The boat has a vent on the deck at the bow, and the top companion way hatch board has open slats. The rest of the boat is built so air can circulate in the bilge, through the hull and cockpit. The only moisture is found on the inside of the cabin roof. Once the companion way is open, and we are out for a sail, the moisture dries up. I have opened a cabin port, and am hoping this will assist with air circulation.