Damp garage...where to put vents...

Discussion in 'General Discussion' started by Moons, Jan 14, 2020.

  1. Moons

    Moons Moderator

    So noticed today that new houses garage suffers from a fair amount of condensation.

    I can't find any vents anywhere (can't see any evidence of floor or wall damp) and assume some ventilation holes will help.

    Question is, where to put them? Down low, mid wall or up high in the eaves?

    I'm concerned that the van has condensation on the windows so want to sort it quickly.
  2. Got any vents in your soffits?
    Purple likes this.
  3. Air bricks. High an low.
    paradox and Moons like this.
  4. Desiccant dehumidifier will help. I have one in both my garages and it’s surprising how much water they pull out. A meaco dd8l junior is highly recommended. Will also add some heat to the garage so it’s not so cold when your working on your van. After spending an absolute fortune on restoration I’m keen to keep our van in rust free condition!
  5. Moons

    Moons Moderator

    No, it’s not unlike one of those air valves on a space ship.
  6. High, low, wherever. Can you open up the eaves? Under the doors? You want plenty of chance for air to circulate and a breeze to waft through.
    mgbman likes this.
  7. This^
    Then you get a flow of air through the garage

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    JT1, Lasty and mgbman like this.
  8. I’ve got no vents in my garage - built 1980’s. However the gap under the door takes care of that. It also means I regularly have to sweep the leaves out.
    JT1, Jack Tatty and mgbman like this.
  9. My garage has 2 air bricks and a nice gap around the up and over door. So lots of air flow. mgb sits in there happily without condensation. My van sits outside without a cover in all weathers and does get some interior condensation as expected and I just mop it up and keep it dry as possible. With a good air circulation in the garage, any type of dehumidifying product would constantly struggle to extract water from the new air which would have a lot of humidity.

    A neighbour used to keep his classic car in his garage in a controlled and sealed cocoon, but that was over the top and expensive.
  10. I'd have thought this was your answer ... is it single skinned, I would expect so?
  11. and rain water blown in.
  12. +1 for the desiccant dehumidifier. Ecoair do one for just over a one’er. Well worth it. Don’t have the van in the garage but keeps the bikes nice & dry :thumbsup:
  13. I have same set up. B) is preferable

    If not going to use dehumidifier you need two things 1) vents and 2) a source of background heat. Vents without heat is useless, as damp winter air just comes in and stays damp. Slightly better than sitting in rain of course. The phenomenon that works is when cold damp winter air comes in through vents, and is then warmed slightly, it is easily dried by the change in temperature to dry air. Strangely warm summer damp air is a lot harder to dry out than cold winter air. This is the phenomenon that is not often understood.

    So if you have a warm damp house in winter that is condensed, like kitchen, and you crack open the window to let cold damp air in it dries the room out extremely quickly. Then think about the same scenario if there was no heating in the kitchen! Damp damp damp.

    B) if using a dehumidifier; as above, you need a desiccant dehumidifier as these work more efficiently in cold temperatures. Seal the garage as best you can and set to pipe drain. I have this set up and easily maintain Californian humidity of 50% all year round. No rust, no condensation
    Skyelectrix and Moons like this.
  14. I had a similar problem, best solution I found was to double skin the roof internally with loft insulation laid between the two .
    Metal sheet roof by the way - the worse ....

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  15. Moons

    Moons Moderator

    Thank you for the replies.

    As it’s rural, and we have local rats and mice I’m trying to limit access.

    I’m wondering if a ventilation fan might help?
  16. W
    without heat, no not at all. As mentioned above, ventilation fan works in houses, because houses are heated. The phenomenon I described
  17. You basically have one single objective and that is to lower the relative humidity.

    If you stood in a damp cold room in front of a fan would it dry your hair or the contents of the room - no.

    If you you apply heat to the fan, so a hairdryer, would this dry your hair - yep.

    People associate heat as doing the drying, what’s really happening is the heat is lowering the air’s relative humidity

    Cold fan or vent is changing nothing, just sane damp cold air passing around, unless you change the temperature of the air also
    Skyelectrix and Moons like this.
  18. My garage is a bit leaky, but I put a door brush strip in and a strip of stormgard foam from Screwfix around the main door and this is easily enough for a humidifier to handle.

    If you go for very mild background heat any slight leaks will help the cold air into the warm garage scenario
  19. Baysearcher

    Baysearcher [secret moderator]

    Stick some vents in, job done.
  20. I reckon he's going to let it out as a studio flat.......

    If you don't want to smash holes in the brickwork than fit some vent grilles in the garage doors.

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