A little help in battling condensation

Here’s a little idea of my training setup, since I’ve moved out of the house to train into a dedicated, glorified shed in the garden. All has been well through the summer, besides it feeing like an oven in the sunshine which can be dealt with by use of a fan and wide open doors.
This week however the weather has gone bitterly cold, and I have noticed condensation on the ceiling after I ride. I’ve barely needed the fan on, but have had the door partly open to allow some degree of air flow
I could do with your cheapest/most convenient solutions please, to avoid damage to my new building as the sweat collects above me! Do I varnish/coat the inside? Just wipe it down each time?
As far as I’m aware it’s pre treated wood, but I’m not 100% sure on the inside

I think the best option would be to increase the air flow, so that the condensation does not happen any more. I am not able to tell what would be the best way to do that.

Improve ventilation and or buy a condensing dehumidifier to run in there. Open the door all the way and use the fan to pull in fresh air.

I have a ‘shed’ gym although it’s OSB lined and insulated with 25mm polystyrene sheets, I added some adjustable vents that slide open/shut. I usually leave them open a crack and have the door open while I’m training. I also have a 6ft thermostatic tube radiator that keeps the inside from going below 8C. No condensation issues after several years.

Usually sheds are draughty enough to not need vents though - is the moisture there the following day?

I’d agree with this, get the door open more and see if that stops the condensation. If you’re still getting issues run a dehumidifier

I train in our conservatory and with the door closed condensation quickly builds up even when just noodling around on a Z2 ride, with the door open there’s no sign of condensation at all

As others said, the condensation issue is ventilation issue. Google some YouTube about attic ventilation. Those principles are the same. Essentially, the attic must have adequate ventilation, otherwise you risk mold due to the temp from inside the house leaking into the cold attic and causing condensation.

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Maybe I’ll try moving the setup around then, so that the airflow directs around to the door and keep it further open! Failing that, maybe a dehumidifier. I’ve only had it a few months so yet to find out how it truly behaves over time


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If you’re in a cold environment, you def don’t want to open the door all the time.

Best bet would be to grab a decently powerful dehumidifier off Kijiji / similar. Note: These things will toss a fair bit of heat. So if your shed is always very cold, that could be a welcome thing. If you struggle already w it being too warm, this may seem odd, but putting a second hand AC might be your best bet. Be careful; they have minimum exterior operating temperatures.

Ultimately, you need to bite into the fact you’ve set yourself up w a decent challenge to overcome: Getting HVAC right is more and more challenging the smaller the space, and the more extreme the conditions [variance in indoor vs outdoor temp, you cranking out pretty extreme amounts of moisture while you WO, and pretty much the entire air volume being dumped every time you open the door].

You can overcome these challenges, and have a “perfect” setup. Strongly recommend you bite into them and find the right, powerful solution, and then enjoy. Rather than dinking around with sub-ideal solutions, and frustrating yourself with subpar results for a few weeks! :slight_smile:

EDIT: Best option might be to have that dehumid, but leave it off so it isn’t tossing too much heat, if your rides are only 60 - 90 mins, and then running it for a while after your ride, to re-dry the shed? But won’t work if your rides are 90 - 240+ mins. #swampshed !! LOL


I have a 600 gallon aquarium built into the wall with a room for equipment behind it. Bathroom motorized ceiling vent. Heat and A/C vent. This works 90% of the time. When it’s super humid here in Texas I have to open the door to that room. If that wood is untreated it will absorb moisture.

Dehumidifier or leave the door open, or some sort of fan to exchange the air with the outside. Those are your only solutions really. A window air conditioner works in the summer. Side note - I would 100% cut a hole in the wall to mount an A/C if I needed to, or even put in a dedicated mini split if I was training in there a lot. Mini Split / heat pump can heat too.

I deal with the same thing in my garage where I train.

Add a roof vent at the apex.
Same thing will happen in a RV in winter.
If you don’t crack the roof vent open before bedtime, you’ll get rain drops falling during the night.


I’d install a powered bathroom vent fan with the exhaust at the highest point of the ceiling. For what it’s worth, the water vapor in your breath is likely the biggest contributor to the condensation, happens even if not sweeting or breathing hard. There’s no way to avoid exhaling moisture into the room, so you need to constantly exchange the air with a fan vented to the outside and/or use a dehumidifier. We have a camper van and condensation is a constant fight, always have to run the roof fan to keep it in check.

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On top of increasing ventilation, which is the correct answer to your question tho maybe also complicated to do immediately yourself, you could buy and use some water resistant paint that is intended for ceilings above a bathroom shower.

External grade varnish (yacht varnish?). I have the fans on and the door a jar and don’t have condensation issues in my mancave. Plenty of books/ paper which a very susceptible to moisture.

Walls are insulated and lined, and then OSB board. Ceiling is “insulating” foil, now mainly covered with jerseys. I have sealed the gaps, but far from air sealed I imagine.

Just be aware that a lot of electrical dehumidifers need a minimum operating temp. I did use moisture traps, but then I’m leaving the door ajar in damp Ireland so questioned the use. My book test is enough for me (rightly or wrongly).

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Exterior varnish ok, but avoid proper yacht varnish, it never sets, stinks of VOCs (volatile organic compounds)is full of nasty chemicals that can cause contact dermatitis. Ask me how I know, ok I’ll admit it, I used it on my kitchen table.

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Panasonic whisper fan through ceiling. Cost you about $120. Pony off the light switch for power. Get 20’ of romex and install it yourself. YouTube is your friend. And you’ll feel super capably afterward. :blush: not that you’re not already. But you’ll feel super SUPER capable once you’re done.