How to Stop Condensation on a Boat (UK Winter Survival Guide)
Updated: Apr 26
👋 Our first winter… was damp 😅
We didn’t realise how bad condensation would be until our first winter onboard.
Condensation on a boat is one of the biggest challenges of liveaboard life in the UK — especially during winter.
We’re talking dripping windows, damp bedding, that slightly cold, clammy feeling no matter how much you try to cosy things up… not the vibe.
The worst of it was under our mattress. We ended up with mould on the foam and even the foam covers — which was honestly a bit of a nightmare.
Luckily, my mum came to the rescue. She literally brought her sewing machine onto the boat, cleaned everything, and sewed it all back together for us. Absolute hero behaviour!
Since then, we’ve become a lot more aware of airflow, moisture, and what actually works (and what really doesn’t).
If you’re still figuring out how boat life works day-to-day, this guide covers the basics: How to Live on a Boat in the UK
💧 How do you stop condensation on a boat?
To stop condensation on a boat, you need to control moisture and improve airflow.
The most effective methods are:
Using a dehumidifier (or two)
Running a heater to reduce damp air
Improving ventilation (opening hatches/portholes)
Allowing airflow under mattresses and cushions
Avoiding trapped moisture from cooking and drying clothes
On our boat, a combination of a diesel heater, two dehumidifiers, and lifting the mattress daily made the biggest difference.
💧 Why boats get condensation (and why it’s worse in the UK)
Condensation is basically unavoidable on boats — especially in the UK.
You’ve got:
Cold air outside
Warm air inside
Moisture from breathing, cooking, showering
That warm, damp air hits cold surfaces (like your windows or hull), and boom — water everywhere.
⚠️ Why it’s such a problem
It’s not just annoying — it can actually cause real issues:
Mould (as we learned the hard way 🙃)
Damp bedding and clothes
A colder-feeling boat overall
Long-term damage if left unchecked
🔧 How to stop condensation on a boat (what actually worked for us)
After a lot of trial and error (and one mouldy mattress incident), this is what’s made the biggest difference.
🔥 Airflow under the bed (GAME CHANGER)
We now have a mesh layer under our mattress to allow airflow.
During the day, I lift the bed up so the dehumidifier can properly get underneath and dry everything out.
This alone has made a massive difference — no more trapped moisture just sitting there.
💨 Dehumidifiers (we run TWO 😅)
We’ve got two dehumidifiers running pretty much 24/7.
One is what we call “the beast” (Meaco DD8L)
Holds loads of water
Kicks out a surprising amount of heat
We often stick it in the bathroom after showers to warm it up and dry it out
The other one is virtually silent (which is great)…
BUT it blows out cold air, which I’m really not a fan of
Personally, I wouldn’t recommend this type — I’d go for one that kicks out heat
We empty both of them every single day — they pull out a lot of moisture.
Only downside?
They dry the air out so much it can feel like they’re sucking the moisture straight out of your mouth 😅 Staying hydrated is actually more of a thing than it was in our house.
Also worth noting: They do use a fair bit of electricity, so keep that in mind if you’re budgeting. It’s one of those hidden costs that adds up over time — we break those down properly here: Hidden Costs of Living on a Boat in the UK If you're planning your setup, we’ve shared exactly how we manage power onboard here: How to Power Remote Work on a Sailboat
🔥 Heating makes a huge difference
We ended up getting a diesel heater after our first winter — and honestly, it made a massive difference.
It doesn’t just make the boat warm, it helps reduce moisture in the air too.
Without it, I think we’d still be fighting a losing battle.
🍳 Ventilation when cooking
When I’m cooking, I always open the portholes above the cooker.
It’s such a small thing, but it really helps stop steam building up inside the boat.
Otherwise, all that moisture just ends up on your windows (or worse… your bed).
🧺 Being more mindful (the boring but important bit)
After the mould situation, we’re just way more aware now:
Letting air circulate wherever possible
Not trapping damp in closed spaces
Lifting cushions and mattresses regularly
It’s not one big fix — it’s lots of small habits that add up.
❌ What doesn’t work
Things we tried that didn’t solve the problem:
Just wiping down windows (pointless long-term)
Ignoring it and hoping for the best (😂 absolutely not)
Not ventilating enough
Condensation doesn’t fix itself — you have to actively manage it.
🧰 Our exact setup
Right now, this is what’s working for us:
Diesel heater
Two dehumidifiers (one heat-producing = best)
Mesh under the mattress
Lifting the bed daily
Opening portholes when cooking
It’s not perfect, but it’s made the boat feel so much drier and more comfortable.
We also started keeping track of what was working (and what wasn’t) during winter — otherwise it’s easy to forget what actually made a difference. That’s part of why we created a simple onboard logbook to keep everything in one place.
🤔 Can you completely stop condensation on a boat?
You’re never going to completely eliminate condensation on a boat — especially in the UK. But you can get it under control to the point where:
your bedding stays dry
your boat feels warm
and you’re not battling mould every few weeks
And trust me… that makes all the difference.
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