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Calculating the rectangular area in a hipped roof

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  • 03-12-2019 5:54pm
    #1
    Calahonda52
    Registered Users Posts: 12,193 ✭✭✭✭


    The question arises when sizing PV panels.
    See the attached picture.

    Assuming the roof pitch is 30 Degrees and that the hip angle is 30 also, the question is how do you calculate the area of the rectangle inside the parallelogram, as the PV panels can only go inside this.

    Calculating the roof slope distance[ hypotenuse ] is okay, as I have the base( half the building width), and the hypotenuse/adjacent angle.

    The other way of asking the question is what is the bottom left angle of the //ogram
    Thanks as always.

    “I can’t pay my staff or mortgage with instagram likes”.



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    #2
    mickdw
    Registered Users Posts: 23,260 ✭✭✭✭mickdw


    Not sure I understand what you are asking.
    Is it the case of a hip roof cutting into another hip and you are querying the biggest rectangle you can fit on the roof.


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    #3
    Calahonda52
    Registered Users Posts: 12,193 ✭✭✭✭Calahonda52


    mickdw wrote: »
    Not sure I understand what you are asking.
    Is it the case of a hip roof cutting into another hip and you are querying the biggest rectangle you can fit on the roof.
    .
    Yes, for the one marked with the arrow, given the two 30 degree angles

    “I can’t pay my staff or mortgage with instagram likes”.



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    #4
    mickdw
    Registered Users Posts: 23,260 ✭✭✭✭mickdw


    Well of you are happy to assume the same slopes,
    The length of the biggest rectangle possible will be the length of the fascia less half the width of the building which you already know.
    The height of the biggest rectangle is the same as the length of the roof sloped surface.


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    #5
    mickdw
    Registered Users Posts: 23,260 ✭✭✭✭mickdw


    Example if 30 degrees and half width is 5m
    Cos30 = 5/slope
    0.866 = 5/slope
    Slope= 5.77 or 1.1547 times half width for all cases using 30 degrees.


    Length of max rectangle = length of fascia at gutter position less half width (5m in my example) if all slopes are equal.


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    #6
    Calahonda52
    Registered Users Posts: 12,193 ✭✭✭✭Calahonda52


    Thanks for this.
    .
    Clearly I did not explain the problem correctly.
    .
    Went out on site and measure the hip angle, its close to 50 degrees

    “I can’t pay my staff or mortgage with instagram likes”.



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    #7
    mickdw
    Registered Users Posts: 23,260 ✭✭✭✭mickdw


    Its 49 degrees if all 30 degrees.
    Inverse tan of 1.15
    That is the angle the hip makes with the actual roof surface.


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