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 prevent mould and mildew



Why do we get mould and mildew on a boat?
Mould and mildew are normally caused by moisture in the air condensing in to water droplets, creating an ideal environment for the creation of mould and mildew. There is always some moisture in the air, and it doesn’t cause us many issues during the warmer summer months, but as cold air doesn’t hold as much moisture as warm air, in the winter we get a dramatic increase in condensation. Condensation creates an ideal starting point for mould and mildew, leading to damage to furnishings, wood, electronics and not to mention lots of cleaning at the start of next season.

What can we do to prevent this?
One option is to provide ventilation to areas prone to mould spores developing. This can be quite difficult on boats however, as structures they are designed to be as well sealed as possible, and to prevent air and water getting in to them as much as possible. It’s difficult to leave windows and hatches open as these can create an entry point for rain, as well as obvious security issues. If you have Dorade or mushroom vents, these can normally be left open over the winter however. Another way of tackling this issue is to heat the air within the boat by using small tube heaters or a frost heater. This allows the air to retain the moisture and not allow it to condense on surfaces. Heating certainly helps to prevent the growth of mould and mildew, but boats are also often not all that well insulated, so can be a more expensive way of curing the problem. A third option is to use a dehumidifier. Dehumidifiers scavenge water from the air, collecting it in a tank or draining it in to a sink and therefore outside the boat. Dehumidifiers work well, and don’t use much power once the initial moisture has been removed from the air. But it’s important to buy the correct type of dehumidifier for use on a boat.


Types of Dehumidifier
Dehumidifers fall in to three categories: Passive (not powered by electricity), compressor and desiccant. Passive dehumidifiers are essentially crystals that absorb moisture. We often see these in miniature form in small packets supplied in the packaging of goods. These can be excellent at helping to reduce moisture in small areas such as cupboards and lockers, but aren’t really suitable for an entire boat, for that you will need an electric dehumidifier, and these fall in to two categories: compressor and desiccant. Both types work very well, but compressor types can struggle in the lower temperatures often associated with winter. Desiccant use slightly more power, but work very well in lower temperatures. They normally heat the air slightly too, helping to prevent condensation further. Which type is right for you? If you heat the boat separately, or for warmer environments such as domestic use, then a compressor type will work well. If you do not heat the boat then our recommendation would be to use a desiccant type of dehumidifier as this will work effectively in lower temperatures.

Other ways to prevent mould and mildew
Whatever type of dehumidifier or heater you use, it’s also worth checking for any other sources of moisture within the boat. Leaks in pipework and window seals will allow water in to the boat which will also add to the moisture inside the boat. Mould normally forms initially in areas where the air isn’t free to move, such as in cupboards or narrow gaps. For this reason allowing air to circulate as much as possible is essential. Leaving cupboards, fridges and lockers open will help, and fit vents where possible. It’s also well worth considering removing any soft furnishings altogether. They are much more likely to remain mould-free stored safely in your house than in the boat (don’t just throw them in an un-heated garage though – this isn’t any better than leaving them aboard!). Another tip is to not use your cooker to heat the boat if you visit it during the winter: gas cookers also generate moisture when they burn, something like an electric fan heater (safety first – never leave unattended), frost heater or oil filled radiator is much better for warming the boat when doing winter DIY projects. Using a product the resists the formation of mould and mildew such as Tea Tree oil is an excellent idea too. This product is naturally antiseptic and anti-microbial, helping it to prevent mould spores before they happen. If you haven’t tried our August Race Boat Bomb yet either then that’s well worth a go – it coats the whole interior with an anti-mould formula at the start of the winter and helps prevent mould forming over the entire winter period.




Happy Sailing!