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  1. #1
    Join Date
    Jul 2014
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    Newcastle, Australia
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    Default Stopping condensation on colourbond roof

    Hi all.

    Just finishing off a small storage area (doors and flashing this week) and I'm after advice on how to stop condensation forming on the underside of the roof. It's just a single colourbond roof. Any thoughts or ideas appreciated.

    TIA

    ...


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  3. #2
    Join Date
    Nov 2006
    Location
    Rockhampton
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    62
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    2,236

    Default

    Condensation happens as a result of hot/warm moist air meeting a cold surface, also referred to as dew point.
    To stop the condensation you need to stop the hot moist air from coming into contact with the cold surface, insulation of some sort is usually the solution here, a few other things you could do is remove the moisture from the air or keep both air temps on either side (of the colourbond) the same, this usually would be some form of forced ventilation (fan).




    Pete

  4. #3
    Join Date
    May 2013
    Location
    Somerset Region, Qld, AU.
    Age
    66
    Posts
    602

    Default

    Quote Originally Posted by Tritonitis View Post
    Hi all.

    Just finishing off a small storage area (doors and flashing this week) and I'm after advice on how to stop condensation forming on the underside of the roof. It's just a single colourbond roof. Any thoughts or ideas appreciated.

    TIA

    ...
    ,

    I had the dreaded condensation problem in my Colourbond roofed workshop until a year. Some mornings, the inside of the roof would be soaking wet with condensation and dripping everywhere. I used to have to cover all the machinery and all timber and any work in progress with tarps every night, and even then I was getting huge amounts of rust from the high humidity. Workshop Roof Insulation.jpgThe roof sheeting on my workshop was very old and corroded and due for replacement anyway, so in the process of installing new roof sheeting, we decided to insulate the workshop roof.

    I'm not allowed on ladders any more, so I got a local builder to do the job for me. After removing the old roof sheeting, and replacing the rusty purlins (rust caused by the condensation buildup), he first laid wire netting loosely across the purlins, and tied off the wire netting by wrapping it around the purlins at each end, twist wiring the netting to secure it. He then laid 50mm thick foil backed Pink Batts on top of the wire netting (over the purlons) with the foil side down. The the roof sheeting was screwed down in the normal manner.

    The wire netting was loose so that it hung down 50 to 60 mm between the purlins, to make room for the insulation, so that the insulation was not compressed between the purlins. The wire netting was not the standard stuff that you'd use for a chook pen. The netting was purpose designed for the job, but not expensive.

    There seem to be varying opinions floating around as to whether the foil side of the insulation bats should face up or down. When the builder contacted the Bats manufacturer for guidance, the manufacturer said that in this instance it didn't really matter whether the foil side faced up or down. I choose to have it installed foil side down as that made the ceiling of the shed very reflective and has greatly improved the effectiveness of the lighting in the shed.

    The insulation has been very effective. I no longer get any condensation in the workshop, at any time of the year. And as an added bonus, the shed is much cooler in summer. The outside temperature now has to get up to 36 degrees outside before it's too hot inside the shed. Before insulation, inside the workshop was usually 5 to 10 degrees hotter than outside on a hot summers day. This winter, the shed also seems to have been a few degrees warmer on cold mornings, so it seems that the insulation is helping there as well.

    The cost of adding insulation under that roof sheeting was a matter of a few hundred dollars for a roughly 10 x 10 meter roof. Seeing you already have your roof fitted, one way to proceed might be to remove the roof and fit the insulation. Alternatively, I have seen one local shed where the bloke installed the insulation bats without removing the roof sheeting. He used screws with "penny washers" to secure the wire netting to the underside of the purlins, and held the insulation up that way.

    Hope that information helps,

    RoyG
    Manufacturer of the Finest Quality Off-Cuts.

  5. #4
    Join Date
    Jul 2014
    Location
    Newcastle, Australia
    Posts
    77

    Default

    Thanks for the replies.

    I was thinking about adding insulation but couldn't work out how to do it without screwing up through the roof.

    I may end up making up a small framework to hold the insulation up against the roof.

    I'll trawl the net over the next couple of days and see if there is an off the shelf solution.

    Thanks again



    edit: I just thought of a way to add some sarking or similar pretty quickly.

  6. #5
    Join Date
    May 2012
    Location
    Woodstock (Cowra)
    Age
    74
    Posts
    3,372

    Default

    Polystyrene foam panels with appropriate glue (especially formulated for the foam) to under side of roof or use the new bubble foil insulation and glue directly to roof (it is also fire retardant treated) and the foil will help with lighting
    The person who never made a mistake never made anything

    Cheers
    Ray

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