Condensation in a rooftop tent is caused by you, not by the weather. Two
people breathing overnight put roughly a litre of moisture into the air. When
that warm, damp air meets colder canvas or a colder shell, it turns back into
water on the surface. It is physics, it happens in every tent ever made, and it
is almost entirely preventable.
Ventilate, even when it is cold
The instinct on a cold night is to zip everything shut. That is exactly what
causes a wet morning. Leave vents or windows cracked at opposite ends so damp air
has somewhere to go and drier air can replace it. A small amount of airflow costs
you very little warmth and takes most of the moisture with it.
On The Horizon rooftop tents use 350gsm ripstop poly-cotton canvas, which
breathes rather than seals. That is deliberate. A fully sealed tent keeps rain
out and traps everything you breathe out, so you stay dry from above and wake up
wet from the inside.
Keep wet gear out
Boots, jackets and towels brought inside will give up their water overnight
into the air you are sleeping in. Leave them under the awning, in the vehicle or
in a dry bag. Wet dogs are worse than wet boots.
Air has to move under the mattress
The mattress base is where condensation is least visible and does the most
damage, because it sits between a warm body and a cold platform with nowhere to
escape. Every On The Horizon rooftop tent includes an anti-condensation pad under
the mattress and a moisture barrier through the base, which is what keeps air
moving underneath rather than water pooling there.
If your tent does not have one, an anti-condensation mat is the single best
thing you can add.
Where you park changes the result
Cold air and moisture settle into low ground. Camping in a gully, beside a
river or on a damp flat gives you a colder, wetter night than parking twenty
metres up the slope. On a clear, still night the temperature drop is sharper and
condensation is worse, which catches people out because clear weather feels like
the safe choice.
Dry it before you pack it
Condensation that is wiped away in the morning is nothing. Condensation that
gets closed up inside a tent for a fortnight is how canvas develops mould and
odours it never loses. If you have to pack up wet, open the tent again at the
next stop, or at home, and let it dry properly before it goes away for any real
length of time.
Common questions
Why is my rooftop tent wet inside when it did not rain?
That is condensation, not a leak. Warm damp air from your breathing meets the
colder canvas or shell overnight and turns back into water. More ventilation,
keeping wet gear outside and airflow under the mattress will fix most of it.
How do you stop condensation in a rooftop tent?
Ventilate at both ends even when it is cold, keep wet clothing and boots out
of the tent, make sure air can move under the mattress with an anti-condensation
pad, and avoid camping in low, damp ground. On The Horizon rooftop tents include
an anti-condensation pad and a moisture barrier as standard.
Does an anti-condensation mat actually work?
Yes. It lifts the mattress slightly so air can circulate underneath instead of
moisture being trapped between a warm body and a cold platform. It is the most
effective single item for the money.
Related guides
How to Prevent Rooftop Tent Condensation
Condensation in a rooftop tent is caused by you, not by the weather. Two people breathing overnight put roughly a litre of moisture into the air. When that warm, damp air meets colder canvas or a colder shell, it turns back into water on the surface. It is physics, it happens in every tent ever made, and it is almost entirely preventable.
Ventilate, even when it is cold
The instinct on a cold night is to zip everything shut. That is exactly what causes a wet morning. Leave vents or windows cracked at opposite ends so damp air has somewhere to go and drier air can replace it. A small amount of airflow costs you very little warmth and takes most of the moisture with it.
On The Horizon rooftop tents use 350gsm ripstop poly-cotton canvas, which breathes rather than seals. That is deliberate. A fully sealed tent keeps rain out and traps everything you breathe out, so you stay dry from above and wake up wet from the inside.
Keep wet gear out
Boots, jackets and towels brought inside will give up their water overnight into the air you are sleeping in. Leave them under the awning, in the vehicle or in a dry bag. Wet dogs are worse than wet boots.
Air has to move under the mattress
The mattress base is where condensation is least visible and does the most damage, because it sits between a warm body and a cold platform with nowhere to escape. Every On The Horizon rooftop tent includes an anti-condensation pad under the mattress and a moisture barrier through the base, which is what keeps air moving underneath rather than water pooling there.
If your tent does not have one, an anti-condensation mat is the single best thing you can add.
Where you park changes the result
Cold air and moisture settle into low ground. Camping in a gully, beside a river or on a damp flat gives you a colder, wetter night than parking twenty metres up the slope. On a clear, still night the temperature drop is sharper and condensation is worse, which catches people out because clear weather feels like the safe choice.
Dry it before you pack it
Condensation that is wiped away in the morning is nothing. Condensation that gets closed up inside a tent for a fortnight is how canvas develops mould and odours it never loses. If you have to pack up wet, open the tent again at the next stop, or at home, and let it dry properly before it goes away for any real length of time.
Common questions
Why is my rooftop tent wet inside when it did not rain?
That is condensation, not a leak. Warm damp air from your breathing meets the colder canvas or shell overnight and turns back into water. More ventilation, keeping wet gear outside and airflow under the mattress will fix most of it.
How do you stop condensation in a rooftop tent?
Ventilate at both ends even when it is cold, keep wet clothing and boots out of the tent, make sure air can move under the mattress with an anti-condensation pad, and avoid camping in low, damp ground. On The Horizon rooftop tents include an anti-condensation pad and a moisture barrier as standard.
Does an anti-condensation mat actually work?
Yes. It lifts the mattress slightly so air can circulate underneath instead of moisture being trapped between a warm body and a cold platform. It is the most effective single item for the money.
Related guides