Excerpted from the Internet below.
Pete and Rats
LiveAboard Magazine & Marine Chandlery
Living With Winter
The following is a compilation of various letters from boaters and how they have dealt with the problems of winter condensation and heat.
I have been interested in the current letters concerning keeping warm in the winter.
Having spent 11 years aboard various boats I did find that warmth is of primary
importance in the cold winter months in any part of the country.
I found that small wood heaters are available for boats and produce a wonderful dry
heat. In fact the one I had required a kettle of water on top to add humidity. I can still
remember the winter storm in 1982 when the snow was piling up and I was walking
around inside in a pair of shorts and "T"shirt. You get some strange looks from
people passing by during such times. The particular stove we had would accept a
lump of coal for keeping the fire going all night.
Still available in many areas are the CAT heaters that use propane
and are very
effective in small spaces. We heated our Columbia 34 quite nicely with our
thremostatically controlled CAT heater.
One last thing to remember for those electric heater folks. Keep the air moving. If
possible leave windows
or hatches open a little for good air movement. This will aid
in keeping mildew and condesation to a minimum. Here's wishing you all warm
evenings and toasty mornings durning the next couple of months. Gentle breezes...
One of our readers wrote with some questions. He was wondering where in the boat
the dehumidifiers were placed and where he could purchase the 3/4" closed cell
foam used to insulate the boat.
The closed cell foam is available through Tacoma Foam Rubber in Tacoma,
Washington. They get their rubber in approximately 4 foot by 8 foot by 3 foot
bisquits. They then cut it into any size or shape desired. I have had matresses and
cushions custom cut and laminated by them and they matched the template perfectly
on odd shaped pieces. The closed cell foam as I recall was a layer of 1/2" with a
1/4" layer laminated to it.
One side had white vinyl on it and we used it for the finished side and used contact
cement to glue the rubber faced side directly to the fiberglass hull. We cut out the
exact size (or as close as possible) to fit in closets and cabinets. We then used duct
tape on the edges to seal out moisture. Anyplace the warm air can contact the cold
hull there will be frost and/or dew. We also covered the through hull bolts from our
sail rigging. It had been in the sailboat for about 9 years when the boat burned out
from under us and was working beautifully.
The only thing I had to do in those 9 years is replace a piece of duct tape
occasionally. As per the dehumidifiers, it doesn't really matter too much where you
put them as they have fans that circulate the air and relative humidity disburses
throughout the boat and eventually evens out as does temperatures if the air is kept
moving. I have 2 on my current vessel and turn the one closest to the source of
humidity on. If I am cooking a big pot of pasta I turn the one in the galley on. I usually
turn the one on in the stateroom as it is closest to the shower.
We have not had any snow in Petersburg, Alaska yet this year (yes you read it
correctly and it is true) but the temperature is hovering in the 20's and teens with the
clear skies. 2 nights ago I cooked up some linguine and noticed the galley window
starting to fog up. I turned the dehumidifier on until I sat down to eat and the windows
were then clear. I haven't turned either on since. My boat is now 72 degrees with
about 30% humidity. If there are any other questions, feel free to contact me and you
may give out my address to other boaters. My present boat was purchased in Fort
Myers Fla. and brought to Alaska via Panama. I do not consider myself an authority
on tropical sailing. I do however know how to survive in Alaska and cruising in the
Temperate rain forest. I would be happy to help anyone planning a trip to Alaska.
Some time ago I posted a long 'discussion' on condensation aboard and various
ways to deal with it. Since then I've gotten some mail that points out an interesting
fact. You can have relatively dry air and still have a water condensation problem
(and a dehumidifier, heater and ventilation might not help).
The cause is, again, cold surfaces, such as fiberglass hulls and windows
we live aboard a 40 foot sailboat, have a dehumidifier, heat the air, and have
reasonable ventilation. BUT, the warm air holds more moisture than cold. The
dehumidifier can remove significant amounts of moisture from the air, but to live in
the air we breath, you still need about 50/60% relative humidity or you get bloody
noses from the dry air and the wood on you boat (joinery) will start to separate. What
happens is that the warm air comes into contact with the cold surface and the
moisture condenses out (the temp is below the dew-point for the air and the
moisture content). I've noticed pools of water forming in the bottoms of cabinets on
the shelving where it's run down and accumulated. The problem is severe where air
is trapped (poor ventilation) and where cushions and the like (books as well) come
into contact with the hull (bye bye books).
An obvious solution is to insulate the hull, adding (for instance) closed cell foam
insulation (like the 1/4" thick blue-board sold
in Home-Depo) to the hull, but you've
got to glue it down firmly to prevent airflow behind. To add a nice touch, cut the foam
boards to fit first, then apply a nice fabric to the outside surface before using a good
contact cement to adhere the board to the hull surface. The problem here is that you
can't do this everywhere, so you've got to do what you can and run fans during the
day to dry up the accumulation of water before it gets to be a problem. Putting the
insulation between the hull and any cushions you *can't* move would be a minimum.
Drilling holes to add ventilation to cabinets against the hull that you don't want to
insulate might be another minimum stance to take. This is a passive ventilation and
may not gain you much, but if you can add a 'goldenrod' heater to the bottom of the
locker, the heat will rise and create a warm ventilation to help drive off moisture.
In a real cold snap, you will still have problems because of the cold hull and window
surfaces. You just have to live with it, dealing with it as much as possible and drying
out as often as the weather permits.
I'm not a rep for West Marine, but they sell an "Air Dryer" that runs off of 110. They
call it a dehumidifier but it's really just a low watt heater (less than an amp) with the
added feature of a fan to circulate the warmed air and can warm the air in closed
lockers, like under our aft cabin bunk for instance. They also sell the golden rod
things, but buying a lot of them can get costly at about $25 each (10-100 cu.ft.
I do not recommend the chemical dehumidifiers. Done it, been there, thrown away.
Still living aboard,
Darwin Boblet & Family
Originally posted December 15th, 1996
I read the article about damp boats and mildew with great interest. We live aboard a
50 foot aluminum trawler in a temperate rain forest in Southeast Alaska. We receive
in excess of 110 inches of rain per year and temperatures down to as low as minus
20 degrees. We have lived aboard for about 15 years now and we have no problem
with humidity inside the vessel. We do have to scrub some green off the deck in the
spring from the constant snow and rain, but no problem inside. This is our second
vessel we have lived aboard in Alaska.
The first was a 50 foot ketch of fiberglass construction. It was necessary to add 3/4
inch of closed cell foam to the inside of the hull inside all lockers. The foam has a
vinyl coating for easy cleaning of spills. We simply cut and glued it to the hull with
contact cement. We had a Webasto hot water furnace
and a dehumidifier. The
water lines on the webasto ran entirely around the vessel through all lockers. We put
an extra coil in the towel locker so when we got out of the shower, our towels were
heated to 140 degrees. The boat kept itself at 72 degrees all winter. That boat
burned out from under us in the summer of 91.
We bought our current vessel in Florida and brought it to alaska via Panama in the
spring of 1992. We did have to install a heating system to go with its 3 air
conditioning units. We installed a Dickenson Antarctic free standing furnace
. It was
a special order as we wanted 3 coils built inside it for hot water. We then installed a
Webasto hot water furnace
and piggy backed it into the Dickenson. If the Dickenson
cannot keep up with the demand on cold winter nights, the Webasto kicks in and
runs for 5-10 minutes and brings the water up to 140 degrees. It then shuts down. 4
Red Dot units work on thermostats as needed.
We also added 2 dehumidifiers, although we only run 1 at a time. Our rule of thumb
is if we get out of a hot shower and there isn't any fog on the mirror, we turn the
dehumidifier off for two days. We then run it about 5-6 hours a day. We have never
had any problems with mildew in the boat. On the contrary, we often wake up with
dry or bloody noses as the boat gets too dry.
I can empathize with boaters with green shoes but feel there is no excuse for them
on a boat large enough for a dehumidifier. We have one bought from Sears before
they did away with their catalogue and one bought from J.C.Penny since. They are
not expensive but necessary for comfortable living on a boat.
As I write this I am looking out of a starboard window at a light
drizzle. There is an
iceberg about 30 feet across against the next dock over from me and some smaller
ones drifting down the channel. There is a male Stellar Sea Lion (about 2,000
pounder) playing with a Dolly Varden about 100 feet away from us. He has been
feeding here for about an hour. I am sitting at my computer in 72 degrees and about
20 percent humidity.
Life is good.