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Winter Moisture Control

22K views 104 replies 31 participants last post by  Andrew65 
#1 ·
I'm transitioning to livingaboard my boat come April, however, I'm trying to troubleshoot as many problems as I can before I move on. Since the winter is coming to the Mid-Atlantic soon, my major concern at the moment is moisture and condensation. I know all about dew point and all that fun stuff, but what I would really like to know is: What are the most effective ways you all have found to help control moisture aboard? Any and all suggestions and advice are welcome!
 
#55 ·
Tried some cedar breather and roof vent products but they collapsed after use and did not want to re-bound. It lasted us about three weeks earlier this summer. Lucky for us I got it for free, was worth about that..... Hypervent and the other products designed for this use a denser membrane that re-bounds and resists crushing far better. I had the two side by side and the differences are quite a bit.

We are back to using Dri-Dek under the v-berth as nothing we've found holds up as well or stay in place as well. You have to custom cut it but once you do it will last nearly indefinitely...
 
#54 ·
Guys,

The difference between an oil bath electric heater and a fan assisted "ceramic disc" type heater is like the difference between hydronic heat and forced hot air or "scorched air", as we affectionately refereed to it when I was a manufacturers rep in the HVAC business selling boilers, furnaces, radiant heating systems, radiators, baseboard etc. etc...

The oil bath heater acts more like baseboard heat or a hydronic radiator. It moves air, warms it, but does not do much to "dry" it because the surface temp is far to low to dry the air as it moves across the surface.

A fan assisted ceramic disc etc. type heater moves air across a very hot element and in the process the air has some moisture dried out of it. Eventually a good chunk of the moisture in the cabin will be dried using a scorched air type heater whether it be diesel fired or electric.. This is the same with a Webasto, or Espar type FHA diesel furnace as they do a great job at drying the air by moving the moist cabin air across a very hot heat exchanger..

Here in the North East most houses are hydronic heat because it is more comfortable and dries the air out less. Most FHA installations also need duct mounted humidifiers (Maid-O-Mist etc.) so inhabitants of the home don't suffer nose bleeds and dry cracked skin all winter long.

On a boat, that is already a moist environment, you'd actually welcome the dry air that results from moving moist air across a hot element or heat exchanger.

I work on boats all winter long and the ceramic disc "Pelonis" type heaters do a far better job at keeping moisture levels down. When I get to a boat it is often 5F - 30F inside. I can warm the air in the boat, with ceramic disc heaters, without causing much condensation to occur. Of course when I am working on these boats I always try to completely drain the bilge first so the boat is not trying to create its own eco system on top of my own breathing.

I own an number of these ceramic type heaters and they all offer tip over protection and automatic shut down features if the fan becomes blocked and the element gets too hot. The fans in them, like computer fans, draw mA's... I like them because they are small and can be placed out of the way of knock overs etc. because they take up so little floor or shelf space. I have one customer who heats his entire 42' power boat with them and it is very comfortable. His electric bill on the other hand, not so comfortable.....

Be aware that with any 1500W electric heater they draw 12.5A + on the high setting. Just two of them, plus a water heater, EXCEEDS what a single 30A shore power system can handle by over 7.5A.. If you are planning on going electric a second shore power system should ideally be added to handle the massive current used by electric heaters..
 
#56 ·
The squat caframo style ones are almost impossible to tip over, and with main air intake on top and a smaller one on the bottom they work well. I have considered adding mesh over the top air intake so that air can get in even if it gets covered.
I always run the thermostat as low as will keep the cabin warm, that way if the heater vent is blocked it turns off right away.

If it fails, it is OFF. the oil heater tipped over is still hot, even assuming the tip over sensor works. I've already damaged 2 things and burnt myself on the oil heater.



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#58 ·
I was about to ask that too! I find that it does work, my boat is drier with it, but the how is a mystery.

Also to poster re: air space, that is partially true, but having a cold surface and moist air is not great. I am insulating first, then bagging the foam, later hyper dry when i can find a Canadian source. (dry dek is too expensive for me right now).
For lockers inside it will be insulation only. For lockers outside hyper dry only.

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#62 ·
It's good that your shore power system is new, or at least in good condition.
Just remember that while running heaters and appliances, you should try not to exceed 80% of the maximum rating for an extended period of time.

Otherwise you get a syndrome called "boiling the frog". The wiring could get hot, and have a meltdown without ever tripping the breaker. If you're running two heaters, you'll need to shut off a heater momentarily to run your microwave oven or other appliance.

I'm not trying to turn you into an electrical engineer, just do a little simple math in your head:

You have a bucket of 30 amps to work with:
80% of 30= 24 amps safe, indefinite working load.

1500w heater. How many amps? 1500 / 120= 12.5 amps.
2nd heater set to 900w. How many amps? 900 / 120= 7.5 amps

12.5 + 7.5= 20 amps.

Mini Fridge: 6 amp start-up surge, 1.5 amps normal running load.

So, you can safely run one heater full-blast, another heater on 1/2 power, run your mini-fridge, and still be safely within your limits, and not experience any "nuisance tripping" of your circuit breakers.

You can always figure out your electrical loads by reading the labels on the backs of your appliances. They'll always give you something to work with: amps or watts. A casual manipulation with Ohm's Law, and you'll know if you're going to overload your wiring or not. :)
 
#61 ·
This might be an interesting graph. You can see the temperatures we live within and the large difference in which these temperatures can suspend water vapor. Literally twice as much between 10c and 20c (50f and 68f). It looks to me like when you get above 80c or 90c, its capacity become infinite, so I'm still interested in the scorched air concept that Maine suggested.

Also look at the green line with the amount of water suspended at 50% relative humidity (which would feel dry and comfortable) in a nice warm 20c/68f cabin, then keep that water content constant and move the temperature to the left to see what it would have to decline to until it would begin to condensate out. 10c/50f isn't much of a temperature drop, considering how cold the hull is going to be in the winter. While the entire cabin doesn't condensate, its easy to see why bilges, the back of lockers or the spaces behind interior trim do.

 
#64 ·
Well...glad to see that we're in agreement then. :)

Luckily, Tardis and I are not using a hot water heater, and I have no plans to install one. I'll use an electric kettle to make hot water for washing dishes this winter, but that's my limit. I'm comfortable being a minimalist.

Tardis' boat is 25', mine is 30' which is a small cabin volume, so hopefully running at 80% capacity will be adequate. That's why I have the propane heater as an emergency supplemental for those low-teen/single-digit days.

She just needs to understand that she might have to suspend a heater while she runs the microwave, toaster, electric kettle or whatever hair-care appliance she might be partial to.

I frequently touch cords and outlets to feel the temperature, and make sure everything's ok.

Your pictures are very good reinforcement, but at the same time, I don't want to come across as one of those old, dire Sailnetters that make it seem like sailing and liveaboard life are a "deathwatch" (credit to Smackdaddy's faux news article).

It's perfectly safe and enjoyable as long as you're a little more self-aware than the average home owner.:)
 
#67 ·
Tardis' boat is 25', mine is 30' which is a small cabin volume, so hopefully running at 80% capacity will be adequate. That's why I have the propane heater as an emergency supplemental for those low-teen/single-digit days.

She just needs to understand that she might have to suspend a heater while she runs the microwave, toaster, electric kettle or whatever hair-care appliance she might be partial to.
Thanks for posting this. I was actually just making a list of what I'm planing on taking aboard and how many amps each draws. Good to know about the 80% as well... But the real question is; how ever am I going to straighten my hair, microwave the wax for my legs, and run the disco ball at the same time while staying warm?! :laugher
 
#66 ·
Amen to Mainsail's shore power post.

Sail Delmarva: Shore Power Melt-Down

While I do use a 1500W heater, if I need more I use my installed propane heater rather than run 2 x 1500W. In fact, I'm much more comfortable now that I have solar and don't leave the boat plugged in. A shore power connection is always a question mark, compared to solid dry connections.
 
#75 ·
I've spent several winters aboard in two different boats. Had terrible condensation issues the first winter but have coped better ever since. Ventilation is not just inside out. It is also about internal ventilation, making sure compartments are not sealed off. I keep most compartments open at least slightly, such as the sliding door cupboards and bins. I am a big fan of the old style ceramic heaters such as made by Pelonis. They are hard to find and not cheap. Most electric heaters found in stores are crude technology that was used by our grandparents. But good ones can be found. I prefer to have more heaters, running at lower settings. This allows far better distribution of the heat.

In addition to watching load levels (current, amps), it is essential to pay attention to every connection. The connections are the weak point where failure usually happens. A poor connection can heat up hot enough to melt and burn without tripping a circuit breaker because until two opposite wires actually cross and short there is no over-current. Everything AC electric in the boat is basically on an extension cord, as is the boat itself. Feel the connectors often. Make that part of the routine of time aboard. If the connection is very warm, either the cord is too small for the current, or the connection is poor. I use heavy guage cable and connections that can be viewed and cleaned.

I have a keel stepped mast which in the winter is a cold delivery device. I wrapped it with refelectix and that mae a big ifference. My boat has several large ports with frames get very cold in winter and hot in summer. I cut reflectix covers for them and that helps a lot, too.

I use thin foam panels and reflectix to double layer compartments and as many flat or gently curved surfaces as I can. I have big overhead hatches in my boat that are great for light and ventilation in warm weather, but are escape paths for heat in winter. I cut inserts of the thin foam and fit them inside the hatch. Cuts heat loss markedly.

I also use a lot of Damp-Rid. It works great and can be affforable with careful buying. I get the hanging type in 3-4 pack boxes at WalMart, Home Depot, Lowes, and the like. Usually for $8 or so, sometimes less on sale. One of those in the hanging locker makes a HUGE difference. I also use the tub type as it is far cheaper. The refills can be bought in bulk, enough to fill 3-4 tubs for maybe $3. Sometimes the absorbant grains can be bought as sidewalk ice melter for even less cost. I place tubs where they won't slide and have never had one tip. They make a huge difference.

Baking warms the cabin up nicely, too.
 
#78 ·
we are a family of 4 (lots of condensate) living on a 36fter off the magothy. we're currently heating with 2 small ceramic heaters that both heat and dry our boat quite well. haven't insulated yet and still contemplating the bulkhead diesel heater for times when the power goes out (thanks sandy) and when we are on the hook. i will say, we pay a flat fee for electric/liveaboard. otherwise we'd be burning diesel now.
 
#79 · (Edited)
Forgot to mention that a major area of heat loss is through the cabin sole. The cold water is a great conductor of heat out of the hull. I bought some cheap, rubber back carpet runners at KMart and cut to fit the main cabin sole. And some smaller runners for the sole leading to the forepeak. Made a big difference. This year I am about to do same but this time will first put down a layer of thin blue foam. 1/4"? That with carpet over it will do even better.
 
#81 · (Edited)
It's the kind you buy at Home Depot or Lowes. About 6ft by many feet, folded like an accordion to about 6x2. There is thicker pink foam but that is more than I would like under a rug I am walking on.

I buy rugs at KMart because it is cheaper than anywhere else. Each store has about half the same and half different patterns and dimensions.
 
#82 ·
I'm curious about winter moisture and resultant mildew that might accumulate in the bilges, if air circulation is further inhibited by a carpet. Moist air, cold hull = condensation. We have one we use in the summer and have to keep on top of it even then.

Nothing like a carpet on a boat in the morning, however. Even in warm water, the sole is usually cold in the morning. But, we have to keep it well vacuumed and, if not for the air conditioning and dehumidifier, I would think it would eventually begin to stink. It definitely absorbs moisture when we're way from the slip, which is one reason we run the AC about an hour or two every day, whether we really feel we need it or not. Keeps things dry.
 
#84 ·
I'm curious about winter moisture and resultant mildew that might accumulate in the bilges, if air circulation is further inhibited by a carpet. Moist air, cold hull = condensation. We have one we use in the summer and have to keep on top of it even then.

Nothing like a carpet on a boat in the morning, however. Even in warm water, the sole is usually cold in the morning. But, we have to keep it well vacuumed and, if not for the air conditioning and dehumidifier, I would think it would eventually begin to stink. It definitely absorbs moisture when we're way from the slip, which is one reason we run the AC about an hour or two every day, whether we really feel we need it or not. Keeps things dry.
When the outside air is 95% humidity ,changing one batch of wet air for another doesn't dry anything out. The bilge will be near 100% humidity, period, any time there is any water in it.. What causes condensation is a more than 2 degree difference in temperature between the air and a surface. Carpet reduces this difference by keeping the warm cabin air from contacting the hull plate, thus keep the air in the bilge cooler..
 
#86 ·
I like the square interlocking 2x2' from home depot, top surface is tough, easy to clean and very warm. Cut to the right width, easy to cut around posts etc. 20$ did my whole boat and left me two spare tiles. Not too hard not too soft, designed for standing on, and one section can easily be replaced if damaged.

Instant difference in warmth in the boat at floor level, not such a divided temperature range anymore. I meant to carpet over top, but this is easy to clean, and great under foot.

Keeps smells down, and small screws and parts out of the bilge. Easy to lift every square individually for access to hatches, one of the many reasons I scrapped the carpet idea.



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#87 · (Edited)
Although I don't live aboard, I do have a few suggestions from my experience in solving moisture problems in my boat.

First, as Jess pointed out, the key issue is the dew point of the air, which is another way of measuring the humidity. Any surface of the boat that is below the dew point, condensation will occur. Note that dew point is an especially useful way of measuring humidity, because it is independent of the air temperature - all that really matters is whether the temperature of cold surfaces is above or below the dew point.

One problem with small, enclosed volumes like a small boat is that ordinary respiration can fill the air with humidity. If you go to bed with the boat closed up tight (like you would do on a cold evening), much of the water you drink will be exhaled into the boat. The humidity will be there even if the boat is heated. The key is to minimize the cold surfaces that the moist air comes into contact with. If you've ever waken up in a camping tent in November or December, you've likely seen the kind of condensation that can occur.

Jess's pictures show that she is doing a good job at preventing this with her insulation on the sides of the boat. Once other place where I experienced condensation was in the storage under the settees, especially under the waterline. A couple of years ago I posted about how I solved this problem with bubble wrap, which insulated well enough that the air never came into contact with a surface below the dew point. This area is critical, because often life jackets are stored there, and for a liveaboard there may be clothes stored there. These things would be susceptible to mildew, especially under the waterline. I like the Reflectix stuff that Jess is using above her settees, and have been meaning to replace my cheap bubble wrap with it. (One more thing to go onto my list for this winter.)

A dehumidifier can be a great help for a boat that is on shore power. On a 25 footer space is at a premium, so a full sized dehumidifier might be impractical. But a couple years ago I posted a thread about a tiny Peltier-type dehumidifier that I found at Home Depot. It's still going strong, draws about 60 watts and sits on my galley counter, velcro'ed to the shelf behind it (to make it heel-proof). This year I attached a hose to the drain pan that I run to my galley sink so I don't ever have to pour it out.

As for the issue of dampness in the bilge, I think that could depend on whether Jess's O25 is inboard or outboard. If it's outboard, there's a good chance she can keep her bilge 100% dry, which will reduce the problem significantly. If she has an inboard with seepage through the packing gland, she will have a wet bilge, in which case carpet or foam over top would mean 100% humidity all the time in the bilge, which could be problematic. For this I have a question, not an answer. I have always wondered whether adding a small amount of bleach into the bilgewater could knock out any mildew. Maybe a capful every week would need to be added, since continued seepage through the packing gland and cycling of the bilge pump would dilute out the bleach. The risk could be that the bleach could prematurely age the bilge pump and hoses, but I would think that there might be a low level of bleach that could keep the water disinfected. What do you liveaboards think of this?
 
#88 ·
........The risk could be that the bleach could prematurely age the bilge pump and hoses, but I would think that there might be a low level of bleach that could keep the water disinfected. What do you liveaboards think of this?
I have been known to sanitize the bilges on the hard every few years or so. It takes very little bleach to do so. In fact, a bleach bathroom cleaner usually suffices. However, it is immediately followed by a thorough rinsing, so that the chlorine doesn't really sit in the pump or hoses.
 
#89 ·
I think I get what Brent means, essentially that ventilation alone won't help much, if your outside air is almost saturated, you need to make the boat dryer than the outside air, so other techniques are needed.



I put a little pinesol(pine oil has some good properties) or tea tree oil and spray the bilges occasionally. The interlocking floor tiles make this easy.



Personally I don't understand the use of reflectix in boats, except in small hard to work in areas. it's less efficient and not really cheaper than a good insulation. It does well enough, but not great imo.


Since the job is labor intensive, I'd stick with Volara(for continuous lengths) or Armaflex(available in smaller sheets, or a 200' roll)
which has the added bonus of being mold resistant. Price difference is not huge, online in the usa volara is under 10$ a running foot, and 5' wide half inch thick. Thinner is cheaper still.
Both are acoustic damping as well.


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#90 ·
Hi, all! I think the idea about insulating under the settees is a great idea, hadn't thought of doing that. My boat has an outboard, and my bilge is generally very dry. I just updated my photo gallery... I think I'm almost done...for now ;)
 
#92 ·
Year round. I just take it out to spray with cleaner and pressure wash.

1.It fits just fine there, can't see less ventilation being better than more.
2. It gets cut individually and I don't want to play tetris in my boat anymore than I have to.
3. removed, it's just gonna take up more space somewhere else, or get lost. Also the edges are sharp, and I've caught myself on them a few times when laying it all out.

Also, not sure if it's coincidence, but I had a bunch left over, I put it cloth side up in my lazarette. My lazarette and cockpit lockers all leak right now, the only one where things aren't moldy/smelly is the one where they are all sitting on the hypervent. So save all the offcuts, they can be handy!

BTW I removed my foam tiles on the floor while I was pressure-washing the V-berth for paint. Left them off at night, and forgot, my legs were freezing when I was sitting reading, and humidity in the boat was worse than usual.
Put them back into place, and things were much improved :).
 
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