Lockers full of humidity - unusable in winter

[DangerousPirate]

This must be a very common problem for boaties, so I hope there is a good answer.

Basically inside any and all of my lockers and cabinets, the surfaces just turn wet and moldy overtime.

All the items of my lockers, especially fabric, are unable to be kept in the locker as they'd just get wet. Clothes in backs on the bunk instead of the lockers and cabinets. An issue for the cushions as well, I turn the bed cushions after every night to dry them during the day, but the seat cushions have the same issue. Everything that touches the hull somewhere is just wet.

I discussed this with a friend and said I'd want to put some yoga matts or similar in there to insulate the hull surface and prevent condensation (which causes all of this obviously), but he said if I put it in there, it'll just get moldy behind the matt and that might protect my clothes and felted storage boxes etc, but only creates a problem further down the line.

It's a bit problem. Recently I opened the wine "safe", which is under the chart table seat, and I hadn't touched the bottles in there for quite a while and now all the labels are off! Which is the malbec? Which was the cabernet sauvignon?! No one knows until I take the cork off, the labels just disintegrated. Living like a savage now, drinking from unlabelled bottles.

My suit jackets were touching the hull and need a proper dry cleaning job now, as well. Now I am drinking from unlabelled bottles without the proper attire.

So what does the clever mariner do to tackle this problem? Glue down carpet or foam backed vinyl in all the lockers and cabinets (especially near and below waterline)? If it's glued down, it can't mold behind it, can it? And if the insulation is thick enough, it should stop condensation, shouldn't it?

 

[thinwater]

You will have condensation if the hull is below the dew point of the air. There are only two solutions:

• Insulate to raise the temperature of the surface above the dew point. NOT carpet, and the insulation must be totally waterproof, air tight, and sealed to the hull (if water gets in or behind the insulation there will be mold). Cored hulls are best, but I'm guess yours is not.
• Run a dehumidifier and keep the relative humidity low enough that it is above the dew point. Depending on the hull temperature and air temperature, that probably means below 40% RH. Pretty darn dry. You will also need to minimize water from cooking and showering. Run ventilation during these activities, using local vents.

You may need to do both.

You will also need enough air movement in the lockers to keep the hull warmer. An IR thermometer can be helpful for locating drafts and cold spots.

 

[DangerousPirate]

You will have condensation if the hull is below the dew point of the air. There are only two solutions:

• Insulate to raise the temperature of the surface above the dew point. NOT carpet, and the insulation must be totally waterproof, air tight, and sealed to the hull (if water gets in or behind the insulation there will be mold). Cored hulls are best, but I'm guess yours is not.
• Run a dehumidifier and keep the relative humidity low enough that it is above the dew point. Depending on the hull temperature and air temperature, that probably means below 40% RH. Pretty darn dry. You will also need to minimize water from cooking and showering. Run ventilation during these activities, using local vents.

You may need to do both.

You will also need enough air movement in the lockers to keep the hull warmer. An IR thermometer can be helpful for locating drafts and cold spots.

Dehumidifier sounds great, but I am not sure I can run them in all the lockers. I tried those little plastic ones that you put in with the silica inside or whatever it is. Those didn't work that well where I tried. Did basically nothing.


If not carpet, what material do you think is best for this job? Probably some sort of foam sheet then presumably. I just thought of carpet because I know some people use that to decorate and insulate their cabins.

 

[harvey38]

Sounds like a lack of ventilation, I'm just back on the boat after a five month break and everything is fine. I leave the hatches on 'Vent' so whilst they are locked, they remain just cracked open providing fresh air and a slight movement of air so it's not stale.

 

[steveeasy]

I used to have a vented cover over the cockpit and left the hatch open over winter and the boat had no condensation. New boat and hatch boards closed. turn up and full of condensation. So good ventilation is key without running a dehumidifier most of the time over winter.

 

[dunedin]

I used to have a vented cover over the cockpit and left the hatch open over winter and the boat had no condensation. New boat and hatch boards closed. turn up and full of condensation. So good ventilation is key without running a dehumidifier most of the time over winter.

But sounds like the OP may be living aboard, which is totally different from an empty boat in winter.

 

[jaminb]

I am pretty much living on my boat through this winter and am running the dehumidifier (plus warm air heater when cold) constantly during awake hours. To keep the galley work tops clear I am draining to the bilge and emptying, via the bilge pump, a couple of times a day. It is amazing how much moisture I produce! It has been too cold and damp outside to get any useful airflow / exchange through the boat.

The dry air appears to mix with the damp air and provide satisfactory level of humidity. I haven't found any damp or mouldy spots - I will occasionally leave a locker open if I haven't been in there recently.

It is expensive in electricity c. £50/pcm but cheaper than replacing mouldy gear.

 

[Iliade]

My boat is well ventilated and hence pretty dry, but nonetheless I keep a number of plastic boxes aboard for towels, bedding, etc., to keep them in a more pleasant condition:

e.g.
https://www.viking-direct.co.uk/en/p/1101985
and
https://www.halfords.com/tools/stor...6l-heavy-duty-storage-box-and-lid-573846.html

 

[Stemar]

Run a dehumidifier and open all the lockers. Take the contents home and dry them thoroughly. If you've somewhere to keep stuff that you don't absolutely have to have on board, leave it at home.

Finally, the hard bit, find and fix the leaks. That moisture is getting in somewhere. Favourites are windows and deck fittings. Don't ignore it - SY Florence on YT is having to replace their toe rails because of leaks and corrosion, and there's a huge interior refit because the ply interior lining has rotted.

 

[samfieldhouse]

Insulate to raise the temperature of the surface above the dew point. NOT carpet, and the insulation must be totally waterproof, air tight, and sealed to the hull (if water gets in or behind the insulation there will be mold). Cored hulls are best, but I'm guess yours is not.

I absolutely agree with this in principle, particularly about the lining being tight to the hull.
But why not carpet? Both my forecabin and quarters berths have carpet lining on the hull and for the last 10 years it’s worked very well.

 

[Plum]

This must be a very common problem for boaties, so I hope there is a good answer.

Basically inside any and all of my lockers and cabinets, the surfaces just turn wet and moldy overtime.

All the items of my lockers, especially fabric, are unable to be kept in the locker as they'd just get wet. Clothes in backs on the bunk instead of the lockers and cabinets. An issue for the cushions as well, I turn the bed cushions after every night to dry them during the day, but the seat cushions have the same issue. Everything that touches the hull somewhere is just wet.

I discussed this with a friend and said I'd want to put some yoga matts or similar in there to insulate the hull surface and prevent condensation (which causes all of this obviously), but he said if I put it in there, it'll just get moldy behind the matt and that might protect my clothes and felted storage boxes etc, but only creates a problem further down the line.

It's a bit problem. Recently I opened the wine "safe", which is under the chart table seat, and I hadn't touched the bottles in there for quite a while and now all the labels are off! Which is the malbec? Which was the cabernet sauvignon?! No one knows until I take the cork off, the labels just disintegrated. Living like a savage now, drinking from unlabelled bottles.

My suit jackets were touching the hull and need a proper dry cleaning job now, as well. Now I am drinking from unlabelled bottles without the proper attire.

So what does the clever mariner do to tackle this problem? Glue down carpet or foam backed vinyl in all the lockers and cabinets (especially near and below waterline)? If it's glued down, it can't mold behind it, can it? And if the insulation is thick enough, it should stop condensation, shouldn't it?

Sorry to hear that but in my experience not a widespread problem so I guess you are living on board?

 

[ctva]

Like Stemar says, we open all lockers (not deck one obviously) and run a dehumidifier over the winter. This is especially important when you are onboard as we humans put out litres of water in the atmosphere every day.

Outside that, ventilation, ventilation, ventilation. Other than the dehumidifier we have a small solar vent which was a revelation when we first used one on our old boat about 25 years ago. Just the small amount of air movement makes a huge difference.

As to insulation, do not use yoga mats or the likes, expensive and useless. Look at the stuff sold for campervan conversions, foil faced closed cell sticky foam, min 10mm. This should solve, in most cases, the surface condensation without the mouldy back problem.

Just my tuppence worth.

 

[ctva]

I absolutely agree with this in principle, particularly about the lining being tight to the hull.
But why not carpet? Both my forecabin and quarters berths have carpet lining on the hull and for the last 10 years it’s worked very well.

To prevent condensation, you need a vapour barrier then the insulation on the cold surface. Carpet works well to mask the problem but they will still be slightly damp as they do not prevent moisture reaching the cold surface.

 

[PaulRainbow]

Dehumidifier sounds great, but I am not sure I can run them in all the lockers. I tried those little plastic ones that you put in with the silica inside or whatever it is. Those didn't work that well where I tried. Did basically nothing.


If not carpet, what material do you think is best for this job? Probably some sort of foam sheet then presumably. I just thought of carpet because I know some people use that to decorate and insulate their cabins.

I have found that 6mm foam backed vinyl works well to stop condensation in lockers etc.

Ventilation is also essential, we live aboard and have several deck vents, allows ventilation and doesn't get too cold.

 

[simonfraser]

i have fitted computer fans in all the locker sides and one fan to extract air, solar panel on the roof, no damp

(dont live on my boat)

 

[samfieldhouse]

To prevent condensation, you need a vapour barrier then the insulation on the cold surface. Carpet works well to mask the problem but they will still be slightly damp as they do not prevent moisture reaching the cold surface.

Ah interesting. Thank you.
I’m looking at redoing the carpeting so will take this into consideration.

 

[Slowboat35]

Where's the moisture coming from? Substantial amounts of condensation can only come from rainwater leaks or a wet bilge, damp air is much less of a problem as it carries little moisture and flushes through with good ventilation. Fix these and there will be little moisture to condense. (imho water in the bilge is often a major cause.) As said above some ventilation works wonders, that isn't hard to arrange.
Mould only grows in long-term or regularly damp conditions and ventilation helps enormously. Leaving locker doors open or partially open over winter is a good idea, I remove all my under-seating locker tops and store them, with the cushions, separated and upright, upright locker doors wedged partially open and taped to prevent them swinging. Removable floor boards and engine covers open too. Don't leave any compartment lidded or closed up. The levels of insulation possible/practical in a boat won't make much difference if you don't take measures to keep moisture ingress to a minimum.
A dehumidifier is all very well if you have electricity but my feeling is that unless you seal the boat up altogether (which would allow it to do its job) leaving one in a ventilated boat is simply a waste of energy as all you're doing is trying to dry the air that flushed through the boat. Silica gel is all but useless unless you have barrels of it and keep re-drying it, ditto re sealing the boat up. My boat overwinters afloat in the marina as described above with cowl vents and a wedge between the barge-boards and the sliding hatch to ensure a small opening. No problems so far.

 

[thinwater]

Dehumidifier sounds great, but I am not sure I can run them in all the lockers. I tried those little plastic ones that you put in with the silica inside or whatever it is. Those didn't work that well where I tried. Did basically nothing.


If not carpet, what material do you think is best for this job? Probably some sort of foam sheet then presumably. I just thought of carpet because I know some people use that to decorate and insulate their cabins.

Not silica gel. That will never reach the required RH number. A real plug-in dehumidifier. If you are living on the boat, a compressor-type that will remove quarts per day, not a few grams.

Closed cell foam cemented and sealed to the hull. Not an easy job. Carpet is NOT used to prevent mold, it grows mold. The vapor barrier comments were dead on.

 

[doug748]

Living like a savage now, drinking from unlabelled bottles........

My suit jackets were touching the hull and need a proper dry cleaning job now, as well. Now I am drinking from unlabelled bottles without the proper attire.

Just a rehash of what the others have said really. To get that level of wet inside a boat...

You may be doing a lot of cooking esp boiling
You must have topside leaks and maybe multiple ones
There will be lying water/damp materials in shallow bilges or inaccessible places
You are maybe using parafin heat or unvented gas
You may be battening down and have insufficient ventilation

Like many others I don't live aboard, but overwinter without power and the boat is fine. I leave a lot of kit/food aboard and don't have a problem with damp and come nowhere remotely near having food labels coming off. Never. Some of my corned dog tins have been around for 10 years : - ].

Two things: I never fully close the forehatch unless I am at sea (It has a simple wooden cowl for the winter) and I use a cockpit cover all the time - a better solution for a liveaboard overwinter is probably some form of tent.
The latter helps keep lockers dry, keeps out windblown moisture/rain and raises the temp in any sun.

.

 

[Pye_End]

Open lockers.
Ventilate boat.
Keep bilges dry.