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effect of solar radiation on an unheated wall in an unheated house

  • 10-05-2012 10:39am
    #1
    amandstu
    Registered Users, Registered Users 2 Posts: 3,960 ✭✭✭


    If an exterior wall in an unheated house is given a coat of paint so as to absorb solar radiation what will be the effect on levels of moisture in the wall in the medium term ?-

    I am talking about a thick (2 feet) wall with rendering on both surfaces and filled with stones and a binding (lime/sand etc) that will hold moisture.

    So if it is painted white it will reflect the sun and if it is painted black the surface will heat up when the sun hits it.

    And the solar radiation is subject to the usual cycles of day/month etc etc.

    Obviously there are lots of variables but will the colour of the surface have the effect of reducing the levels of moisture in the wall?

    Of course we have to assume also that the source of any moisture is either the air or the damp soil beneath which "wicks up". through the base of the wall.


Comments

  • #2
    Gurgle
    Closed Accounts Posts: 5,064 ✭✭✭Gurgle


    Short answer: Yes
    Long answer: Yes, but its difficult to predict how much difference it will make.

    A surface facing towards the sun can absorb up to 1kW per meter squared, that's quite a bit of heat. Climb up into your attic on a sunny summers day, its a lot warmer in there than outside.

    But as the wall warms, you will lose heat to the air through convection and it will also re-radiate. The heat would also have to soak into the wall to have any effect on moisture, and concrete isn't a terribly good thermal conductor.


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