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Roger Gunkel

Preventing Condensation

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A lot of people will already know all about condensation, but for those that aren't so sure, I thought some ideas might help.

 

If you have a number of windows on your boat, then you will certainly know about condensation problems this time of the year. Double glazing will make a huge difference to the condensation on the windows as well as reducing heat loss immensely and cutting out the constant draughts due to convection. (See the double glazing thread if you want to know more LINK) That is just basic physics, but there is also the perceived idea that stopping the window condensation will increase it elsewhere. That is not neccesarily true, but is sometimes seen as such.

 

Any given mass of air will be able to absorb a fixed ammount of moisture before it becomes saturated. The higher the temperature of that air, the more moisture it can contain. The air volume of a boat is much smaller than a house, so the saturation point arrives quicker than a house would. As windows are usually the coldest surface of the boat and the biggest heat loss, they will reduce the temperature of the air next to them until the dew point is reached and the water condenses on the cold surface. If we double glaze the windows, the air will not make contact with the cold surface and the moisture will be retained as the overall air temperature will remain higher. The downside though is that the air will still contain the moisture as it hasn't chucked it on the windows, so is likely to deposit it on other cold surfaces.

 

Boats tend to be very variable in the quality of insulation, but generally, any hidden surface, under beds, behind furniture, inside cupboards, behind curtains, is going to have little access to the warmer air, which tends to rise. the colder air will reach the colder surfaces and quickly reach dewpoint giving condensation. As these areas are hidden most of the time, moisture will be absorbed into the surroundings, giving mildew and promoting rot.

 

So what can we do about it? Well there are number of things, all or any of which can make a big difference.

We need to replace the saturated moist air with drier air, so ventilation with outside drier air is essential. Naturally in sub zero conditions we tend to keep everything closed up, but certainly during the day, try to open the odd window or the hatch for a while, even if you need to boost the heat a little. A solid fuel stove always draws in air to burn, so a fresh air supply near the stove will bring air in, without creating draughts everywhere. Leave cupboard doors open where possible and leave air gaps behind furniture and under beds. One idea which works very well is to use very low power consumption computer fans to circulate air in otherwise unventilated areas. This will help to move the warmer air around the boat and prevent the closed in areas reaching dew point.

 

Any cold smooth area is likely to promote condensation, but one area which is often overlooked is water pipes. All year round, but particularly in the Winter, the fresh water pipes are extremely cold. As they are frequently run around the edges of the boat, they pass under beds, through cupboards, behind skirtings etc. They will be dripping with condensation if unlagged and are a large contributor to low level moisture. The dripping water will be absorbed into the surrounding woodwork and anything near them, giving mould, mildew and leading to rot. It can be stopped by using very cheap foam pipe lagging from any DIY store, over all of the pipes, hot and cold.

 

ALL smooth areas behind cupboards, under beds, lockers, should be covered with something like thin cord carpet, which should be glued firmly to the surface, leaving no airgaps behind. This should also be carried out on all closed in floor areas, to avoid the bottoms of boxes or stored clothes absorbing moisture.

 

Cut down on production of moisture, by only boiling as much water as you need. Don't leave the kettle on the stove all day, it will give you constant hot water, but also massive ammounts of airborne moisture. Boil the kettle when you need it and save any surplus in a large vaccuum flask. Try to have a window open next to where you are boiling saucepans or kettles. When possible, dry any towels or washing outside the boat. Don't let washing up drip dry, use a tea towel then dry it outside. All these things will save recirculating the same moisture.

 

Finally, you can remove some moisture from the air by using a dehumidifier if you have hookup or a plentiful power supply. Much cheaper, is a few breakfast bowls half full of table salt around the boat, which will absorb considerable ammounts of water. It can be refreshed regularly for liitle cost or even dried out and reused if you can dry it away from the boat.

 

I'm sure others will have useful additions that I have forgotten, but I hope that some of this will help to make the winter less damp and more enjoyable.

 

Roger

  • Greenie 3

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Thanks for that Roger.

 

My widebeam has only portholes so with the larger internal volume I only get small amounts of condensation on the aluminium porthole frames.

 

I have a friend with on a narrowboat with condensation problems on his windows. Would you mind giving us your double glazing film recommendation again please? I told him about it but forgot what it was called and where to buy it.

 

Thanks - Mike

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Thanks for that Roger.

 

My widebeam has only portholes so with the larger internal volume I only get small amounts of condensation on the aluminium porthole frames.

 

I have a friend with on a narrowboat with condensation problems on his windows. Would you mind giving us your double glazing film recommendation again please? I told him about it but forgot what it was called and where to buy it.

 

Thanks - Mike

 

If you follow the 'Link' in Rogers post above you'll find the details in that thread .

Edited by johnjo

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Thanks for that Roger.

 

My widebeam has only portholes so with the larger internal volume I only get small amounts of condensation on the aluminium porthole frames.

 

I have a friend with on a narrowboat with condensation problems on his windows. Would you mind giving us your double glazing film recommendation again please? I told him about it but forgot what it was called and where to buy it.

 

Thanks - Mike

 

Hi Mike,

 

Not sure if you mean the film that I originally used, or the acrylic sheet that I have permanently replaced it with.

 

The film is just called double glazing film, which I bought from Wilkinsons, although I think B&Q do it as well.

 

The acrylic is ecoglaze from www.365plastics.com.

 

Regards,

 

Roger

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Two excellent threads. Thanks to Roger for all the time and effort he's gone to.

 

Our condensation problem is mainly on the metal window framework rather than the glazed area and I was thinking of fitting some form of secondary glazing to see if we could cure it. The 365plastics idea mentioned above seems to be what we're looking for. Unfortunately their site was down when I checked a few minutes ago. Hopefully it is only a weekend thing and they'll be back up tomorrow.

 

We've got drop back vents which would force the secondary layer to be some way from the primary glazing. Has anyone any experience of using the acrylic sheet idea with DBVs?

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Unfortunately their site was down when I checked a few minutes ago. Hopefully it is only a weekend thing and they'll be back up tomorrow.

 

Its been down since Thursday.

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if you have central heating on your boat and you warm the air up inside, when you turn off the heating will the hot air meet the cooler air and cause condensation because of the changing temps.I dont have central heating and i never close the windows,so dont have a problem with condensation but have seen boats where it looks like a sauna up the windows i just wondered if it was to do with the central heating

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Two excellent threads. Thanks to Roger for all the time and effort he's gone to.

 

Our condensation problem is mainly on the metal window framework rather than the glazed area and I was thinking of fitting some form of secondary glazing to see if we could cure it. The 365plastics idea mentioned above seems to be what we're looking for. Unfortunately their site was down when I checked a few minutes ago. Hopefully it is only a weekend thing and they'll be back up tomorrow.

 

We've got drop back vents which would force the secondary layer to be some way from the primary glazing. Has anyone any experience of using the acrylic sheet idea with DBVs?

 

I think the 365plastics site is being rebuilt at the moment, but you can access part of the site via the parent company LINK

 

If by DBVs you mean the top hopper type, then we had the same, just removed the metal retainers either end to reduce the gap. You can still open the hopper, as the shape of the transom retains the glass, or just put the retainers back in the Spring.

 

Roger

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Roger

 

Thanks for the information. Not sure about removing the metal retainers but I'm not on the boat to check at present. However, I think that the glass would "fall" out without the retainer as there is nothing to hold it in the frame.

 

We're talking channelglaze windows.

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if you have central heating on your boat and you warm the air up inside, when you turn off the heating will the hot air meet the cooler air and cause condensation because of the changing temps.I dont have central heating and i never close the windows,so dont have a problem with condensation but have seen boats where it looks like a sauna up the windows i just wondered if it was to do with the central heating

 

If there is any moisture in the air (as there inevitably will be) when it touches a colder surface than itself then that moisture will form on that colder surface, when this happens depends on the amount of difference between those two temps, doesn't matter if it's CH ( doesn't make any difference if CH has just been turned off or not) or open fire tho both these produce a drier air with less moisture content than say a non room sealed gas heater. If you can prevent colder surface dropping below a certain temp in relation to internal temp then you can have a sauna inside and get no condensation tho in that scenario you would need totally unrealistic amounts of insulation.

 

In fact you can get condensation wherever warm moist air meets cold drier air that is what happens if a warm weather front meets cold air, cloud and rain forms. This is what happened in the Chunnel recently when cold air from outside met warm air inside and produced massive amounts of condensation and knackered the electrics.

Edited by nb Innisfree

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if you have central heating on your boat and you warm the air up inside, when you turn off the heating will the hot air meet the cooler air and cause condensation because of the changing temps.I dont have central heating and i never close the windows,so dont have a problem with condensation but have seen boats where it looks like a sauna up the windows i just wondered if it was to do with the central heating

 

I don't think so. Condensation occurs as a result of warm air meeting cool surfaces or cool air - like when you breathe out on a cold day..I can't see it happening as a result of heating being switched off?

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Condensation occurs as a result of warm air meeting cool surfaces or cool air -

Off topic but Woody Allen, back in the days when he was funny. tells a brilliant tale about living in a bedsit in a New York tenement in midwinter in which the central heating was turned up full and couldn't be turned off, but the window above the radiator was broken, and he used to sit on his bed watching tropical storms form over the window ledge. :lol:

Edited by quebec

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Rather than use salt which expands with water & oozes all over the container its in, please try using cat litter.

Static caravan owners who winterize the vans are now moving away from salt to cat litter, it does not make a mess & continues to absorb water ok.

We have used it over the last few years with good results after being given this tip & its cheap :lol:

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great info from Roger. Thanks.

 

 

 

 

 

 

................................... may I also suggest that you should avoid heavy breathing ................................ :lol:

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Which type of cat litter Roger clumping or silica gel? I currently use large quantities of Kontrol Krystals (calcium chloride) quite expensive but works well.

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http://www.nigelsecostore.com/acatalog/Solar_Air_Vent.html

 

I`ve installed one of these-got one bit cheaper but same sort of thing! You can get cheaper ones but be aware of how much air per hour it shifts as the cheaper ones dont move much!

It fits into a 4" mushroom vent hole without any cuttitng of metal-just adjusting the ceiling lining very slightly!

Bonus is that it sucks and blows(!! :lol: ) so will move air in the summer!

I stick mine on in the morning-its in the bedroom-then while its off in the day it charges up to use it in the evening to relieve some of the heat from the stove-I`ve left it on all night and not run out of juice!

You can get marine chrome ones or the conservatory type(wat I got) that comes with three options of colour-the brown actually dont look too bad on a cream roof!

 

Highly recommended!

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Which type of cat litter Roger clumping or silica gel? I currently use large quantities of Kontrol Krystals (calcium chloride) quite expensive but works well.

 

I've only ever used table salt which is extremely cheap in bulk bags. I only about half fill a bowl, so that as the water is absorbed it doesn't overflow.

 

The cat litter sounds like a very good idea although I've never tried it, but doesn't it contain other chemicals for neutralising urine? My wife seems to recall that pregnant women should avoid contact with it for some reason.

 

Silaca gel is also excellent if available at the right price. Calcium chloride is a very effective water absorber and de-icer, but does require more careful handling and storage than Sodium Chloride (table salt)

 

Roger

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As I have said before, we do not suffer with condensation at all on our boat. I don't know why this is but it may be a combination of deep draught, small ports, good insulation or good ventilation. The point being that if R. W. Davis can build boats that don't suffer with condensation problems why cannot other boat builders do the same?

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As I have said before, we do not suffer with condensation at all on our boat. I don't know why this is but it may be a combination of deep draught, small ports, good insulation or good ventilation. The point being that if R. W. Davis can build boats that don't suffer with condensation problems why cannot other boat builders do the same?

 

Something to do with price I believe!

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As I have said before, we do not suffer with condensation at all on our boat. I don't know why this is but it may be a combination of deep draught, small ports, good insulation or good ventilation. The point being that if R. W. Davis can build boats that don't suffer with condensation problems why cannot other boat builders do the same?

you can't look at the boat in isolation.

it's as much about your life style as is it about the boat.

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you can't look at the boat in isolation.

it's as much about your life style as is it about the boat.

 

I am wondering if the mode of heating makes a difference. We never used to get condensation problems (except in the unheated bathrooms) when we had houses with solid fuel heating. We did experience serious problems in a house that was well sealed but had central heating.

 

The heating on our boat is from a Morso Squirrel centrally located with a back boiler feeding three radiators. The stove is situated close to the bathroom and there is a big radiator in the bathroom which room is also well ventilated. Somertimes the large mirror will mist up when one of us is having a shower but as the mirror is above the radiator, it soon clears.

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We are getting zero condensation (apart from a little on the outer port glass which drains outside + bathroom after a hot shower) and that is in all this cold weather and kettle simmering all day and night on the SF stove. It's down to ports, good insulation, adequate ventilation and ventilated DG and the fire kept in 24/7 at a saloon temp of 25c. Get up in the morning and look out through clear dry windows.

 

Not wanting to sound smug but if we can do it then it is reasonably easy to achieve.

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The cat litter sounds like a very good idea although I've never tried it, but doesn't it contain other chemicals for neutralising urine? My wife seems to recall that pregnant women should avoid contact with it for some reason.

I think this is because of the risk of contacting toxoplasmosis bugs, which can be carried by cats and are not good for pregnant women. Clearly only a problem if the litter has been used by cats, rather than as a dessicant.

 

 

MP.

Edited by MoominPapa

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I think this is because of the risk of contacting toxoplasmosis bugs, which can be carried by cats and are not good for pregnant women. Clearly only a problem if the litter has been used by cats, rather than as a dessicant.

 

 

MP.

 

Thats useful to know MP, might try some out then. Thats for moisture absorbtion rather than peeing in :lol:

 

Roger

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