Condensation problem

[snooks]

What you need then, dear boy, is what we call "ventilation". As an added benefit you will find that it makes both combustion and respiration easier.

Two and a half of us spent twenty four hours on the boat last week. A cold, rainy day. We cracked open the forehatch - raised the back by an inch or so - and made sure the main hatch was always a little open. Guess what? No condensation - even when the kettle had boiled.

Seriously, a dehumidifier is a hi-tech elastoplast for a low-tech problem. If it's the only way you can keep your boat dry, something is wrong.

A whole 24 hours? Wow Not a few days in sub zero temperatures then?

And you even boiled the kettle!

Well I guess that's where I'm going wrong, there's me making bread, and cooking dinner, and having 8 people on board for mulled wine and nibbles

Guess you don't think my dorade in the heads is a ventilator, or the mushroom vents I have in the saloon are ventilation, or maybe even the top washboard missing, guess there will be no air getting out of there either then

If the inside temperature of your boat is close to the outside temperature of your boat, there there isn't the temperature difference for the moisture in the air to condense on colder surfaces.

If however you like to be warm and comfortable on a boat and keep her cosy and snug, then moisture in the air will condense on colder surfaces. Like glass windows and metal frames, unless they too are warm as any glasses wearer will know when they go into a pub at this time of year and their glasses are foggy until they warm up

When you're at home tonight take a glass, add ice, gin, tonic and a slice of lime and see what happens to the outside of the glass in a warm room....Condensation yes?

Take a pint of ice cold lager outside on a warm sunny day (can't get more ventilated than that) and what on the outside of the glass?....erm Condensation?

It's about temperature difference not ventilation.

If the inside of your boat is cold when it's cold outside, you won't get condensation, if the inside of your boat is warm when outside is cold, you will.

Dear boy!

 

[Ubergeekian]

A whole 24 hours? Wow Not a few days in sub zero temperatures then?

No. Mutiny, I'm afraid. You just can't get the crew these days.

Guess you don't think my dorade in the heads is a ventilator, or the mushroom vents I have in the saloon are ventilation, or maybe even the top washboard missing, guess there will be no air getting out of there either then

You don't have enough ventilation. Simple as that. Get more or use it better. Mushroom vents are poor things - OK for a small draught when the boat is unattended, but generally not up to the job with sources of moisture aboard.

It's about temperature difference not ventilation.

Feel your laundry on a summer day. It's colder than the surrounding air ... and yet it gets drier! Evaporative mass transfer depends on temperature difference and air flow rate.

When the headlining fell off my Westerly I replaced the stuff under the coachroof but just painted the inside of the hull beside the quarter berths. I expected they'd need some insulation later but no, I haven't found any condensation at all there. Ventilation, laddy, ventilation!

I'm afraid that far too many sailors these days try to solve all their problems with 240V AC. If and when you start sailing away from marinas and shore power, your dehumidifier won't help you!

 

[enterprise]

Bunk condensation

Condensation through bunk matresses is all to common, even worse if your water tank is under the berth, body heat causes the cold surfaces to collect moisture droplets, an easy practical solution is to build your own slats, see picture below for the general idea.

Removable slats mean you can still get to the under berth services if required, easy to assemble and remove when required.

 

[puddock]

A whole 24 hours? Wow Not a few days in sub zero temperatures then?

And you even boiled the kettle!

Well I guess that's where I'm going wrong, there's me making bread, and cooking dinner, and having 8 people on board for mulled wine and nibbles

Guess you don't think my dorade in the heads is a ventilator, or the mushroom vents I have in the saloon are ventilation, or maybe even the top washboard missing, guess there will be no air getting out of there either then

If the inside temperature of your boat is close to the outside temperature of your boat, there there isn't the temperature difference for the moisture in the air to condense on colder surfaces.

If however you like to be warm and comfortable on a boat and keep her cosy and snug, then moisture in the air will condense on colder surfaces. Like glass windows and metal frames, unless they too are warm as any glasses wearer will know when they go into a pub at this time of year and their glasses are foggy until they warm up

When you're at home tonight take a glass, add ice, gin, tonic and a slice of lime and see what happens to the outside of the glass in a warm room....Condensation yes?

Take a pint of ice cold lager outside on a warm sunny day (can't get more ventilated than that) and what on the outside of the glass?....erm Condensation?

It's about temperature difference not ventilation.

If the inside of your boat is cold when it's cold outside, you won't get condensation, if the inside of your boat is warm when outside is cold, you will.

Dear boy!

You need air FLOW ...... dear boy !

 

[snooks]

No. Mutiny, I'm afraid. You just can't get the crew these days.

Boat too cold???

You don't have enough ventilation. Simple as that. Get more or use it better. Mushroom vents are poor things - OK for a small draught when the boat is unattended, but generally not up to the job with sources of moisture aboard.

I see you missed the bit about the top 1/3rd of my companionway missing.

We were sailing through November without the dehumidifier or condensation, so my ventilation is fine thank you very much, it's only when there are climate neutered brass monkeys around that the condensation requires the dehumidifier

Feel your laundry on a summer day. It's colder than the surrounding air ... and yet it gets drier! Evaporative mass transfer depends on temperature difference and air flow rate.

The reason it feels cold is due to evaporation, it's a simple principle that the human body has been using for thousands and thousands of years....

Actually drying depends on three conditions, ambient temperature, air flow and low humidity, the more of the three you have, the faster something will dry or a water will evaporate

Something will dry in an oven with no moving air, so air flow isn't essential

I'm afraid that far too many sailors these days try to solve all their problems with 240V AC. If and when you start sailing away from marinas and shore power, your dehumidifier won't help you!

I don't have a problem with condensation in the spring, summer or autumn, but this thread wasn't talking about the usual sailing season, it was about condensation "when it's really cold outside"

In winter when there is a big temperature difference between the outside and the inside, and condensation is a problem if you want to live onboard, hence this thread.....And while opening all the hatches would reduce condensation by equalising the temperatures and increasing airflow, it also means I'll be stuck in a cold cabin with a mutinous crew

Therefore the more ventilation you would need to combat the increased condensation, the colder the cabin will be, so the more you'll have to heat the cabin to make up for the hot air that is whistling through your cabin to make it habitable.

Remember the three ways of improving evaporation? Temp, air flow and low humidity......It's cold outside, so I don't want to increase air flow with air outside, so I increase the temp inside the boat with heating and use a dehumidifier to lower the humidity and this also circulates the air.

So whilst ventilation would help evaporate the condensation, it isn't a practical solution in the middle of winter if you want to enjoy living on the boat

 

[snooks]

You need air FLOW ...... dear boy !

You don't need airflow to reduce the moisture content, ever heard of a drying oven?

Dehumidifiers these days circulate air, then have fans you know, not crystals over a tub.

You don't have to have moist air from outside the boat coming into the boat to reduce condensation. With a dehumidifier you have nice dry air inside the boat, and it circulates the air for you as it takes condensing forming moisture out

 

[puddock]

You don't need airflow to reduce the moisture content, ever heard of a drying oven?

Dehumidifiers these days circulate air, then have fans you know, not crystals over a tub.

You don't have to have moist air from outside the boat coming into the boat to reduce condensation. With a dehumidifier you have nice dry air inside the boat, and it circulates the air for you as it takes condensing forming moisture out

The point of airflow is to transport the air which has become moisture laden, outside rather than letting it linger around inside. Many things introduce moisture into the air - the most efficient way to deal with it would be to get the stuff out.
In this cold weather (below freezing) the air outside will generally be quite 'dry'. We are talking a fairly moderate flow here - not a howling gale through the boat.

 

[Seanick]

Condensation through bunk matresses is all to common, even worse if your water tank is under the berth, body heat causes the cold surfaces to collect moisture droplets, an easy practical solution is to build your own slats, see picture below for the general idea.

Removable slats mean you can still get to the under berth services if required, easy to assemble and remove when required.

Here is the most valid point so far!!

Most bunk tops are painted ply. Even with holes drilled in, lafrge ones at that, you will still get a soggy mattress.

SLATS are the answer!

Having lived on my last boat for nearly 10 years, all year round, I can assure you that this is all you need, dear boys.

Of course a solid fuel stove does help too, plus ventilation to let that warm damp air out, but that was not the OPs' original question!

 

[puddock]

You don't need airflow to reduce the moisture content, ever heard of a drying oven?

Dehumidifiers these days circulate air, then have fans you know, not crystals over a tub.

You don't have to have moist air from outside the boat coming into the boat to reduce condensation. With a dehumidifier you have nice dry air inside the boat, and it circulates the air for you as it takes condensing forming moisture out

Oh, look what I found on another thread ! Maybe we are ALL wrong and you are right? (thread is not on the subject of a boat but a house loft - same principle applies).

http://www.ybw.com/forums/showthread.php?t=224128

 

[snooks]

The point of airflow is to transport the air which has become moisture laden, outside rather than letting it linger around inside. Many things introduce moisture into the air - the most efficient way to deal with it would be to get the stuff out.
In this cold weather (below freezing) the air outside will generally be quite 'dry'. We are talking a fairly moderate flow here - not a howling gale through the boat.

The point of the dehumidifier is to reduce the moisture in the air so it's not moisture laden, and you don't need to get rid of it.

I'm not saying in the normal sailing weather ventilation isn't the answer, it is. But it's not desirable (for me at least) to have enough air flow through the cabin to take the moisture of living, and heat, away when it's cold at this time of year.

Sleeping with a hatch open at this time of year would make the cabin cold during the night, so instead we run the dehumidifier, and it works superbly well for removing condensation that builds up by breathing during the night

As for the loft thread, lofts need good ventilation with eaves and air bricks etc, it's how they work by removing the warm moist and replacing it with cold air while keeping the surounding surfaces at a temperature where the moisture won't condense

But a loft isn't a living space so it can be cold and well ventilated up there, unlike the inside of a boat. So while the same principles of removing condensation will work on a boat, unless you want your boat as cold as your loft at this time of year, it's time to look at other solutions. Enter stage right the dehumidifier

If you want to fit a loft to your boat to aid ventilation and airflow and reduce condensation, go for it, it works with houses, so it must work on boats

 

[aquaplane]

Ventilation would work on my boat.

A dehumidifier won't work on my boat.

Forced ventilation with warm air will work best.

Insulation will control where the moisture condenses, unless the wet air is removed by ventilating it.

 

[Mrs Sea Mist II]

Ventilation would work on my boat.

A dehumidifier won't work on my boat.

Why not?

 

[Ubergeekian]

Boat too cold???

Nope. Milford Haven too bloody wet.

Incidentally, I was using a halogen heater (yes, shore power, I know, I know). They're bloody good, since as long as you are in the beam you get warmed regardless of boat and air temperature.

I see you missed the bit about the top 1/3rd of my companionway missing.

Nope. And that's your problem, I think. Did you see my bit about having the forehatch open a little as well? You need flow through the boat, not just access at one end.

We were sailing through November without the dehumidifier or condensation, so my ventilation is fine thank you very much

Well, fine for November. "We can't be dragging the anchor - I've put out just as much chain as the last tie we were here."

The reason it feels cold is due to evaporation, it's a simple principle that the human body has been using for thousands and thousands of years....

OK, so you've noticed that evaporation can take pace even when the object is colder than the surrounding air. Ever used a hot air hand drier? Noticed lots of condensation o your hands - which are colder than the air stream?

I don't have a problem with condensation in the spring, summer or autumn, but this thread wasn't talking about the usual sailing season, it was about condensation "when it's really cold outside"
So whilst ventilation would help evaporate the condensation, it isn't a practical solution in the middle of winter if you want to enjoy living on the boat

I think you will find that rather a lot of people live successfully in boats - and houses and even campervans - in winter without dehumidifiers. Some of them even throw cocktail parties.

 

[aquaplane]

Why not?

No power.

 

[Ludd]

I think you will find that rather a lot of people live successfully in boats - and houses and even campervans - in winter without dehumidifiers. Some of them even throw cocktail parties.

GREAT idea to have doors open for through ventilation ---BUT CLOSE THEM while cooking or boiling kettles! I know this works for me living aboard--also stops cooking smells permeating cabins and bedding.

 

[snooks]

OK, so you've noticed that evaporation can take pace even when the object is colder than the surrounding air. Ever used a hot air hand drier? Noticed lots of condensation o your hands - which are colder than the air stream?

The drop in temperature is a by-product from evaporation, which is why mammals sweat. Evaporation is water converting from it's liquid state to it's gaseous state. Condensation is the reverse.

Condensation doesn't form on hands because evaporation is the dominant factor. The surface for gaseous water vapour to condense on has to be below the condensation point for water.

So you had a 240 v heater and ventilation. I have a heater and a 240 v dehumidifier. Two different ways around the same problem.