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Why should ISOBOARD® be installed in the cavity wall?
  

In South Africa it is found that the northern walls of a building are exposed to extreme temperatures. The heat from the outside wall penetrates the cavity and then heats up the inside wall. The inside wall causes the temperature inside the building to rise dramatically. After sunset, the wall does not cool down fast enough and the heat is trapped inside the building. If ISOBOARD® is installed in the cavity wall, it prevents the inside wall from heating up in the summer and cooling down in the winter, which helps in providing a comfortable living temperature inside the building.
  
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How is ISOBOARD® installed in the cavity wall?
  

Walls are constructed leading with the inner leaf, and the insulation fixed to the cavity face of the leading leaf. It is recommended that the inner leaf is constructed before the outer leaf to allow the boards to be fastened to the cavity face of the inner leaf. This gives a slightly enhanced thermal performance and will also prevent moisture that may condensate on the board from penetrating through to the inner leaf.
  
  
Installing ISOBOARD® in the cavity wall:
  
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A section of the leading leaf is built with the first row of wall ties.
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Excess mortar is cleaned from the cavity face of the leading leaf and the boards are placed on sides against the leading leaf.
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The first run of boards may commence below damp-proof course level to provide some edge insulation for the floor.
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Brick or block gauges are to be set such that cavity ties occur at 600mm vertical spacing in order to coincide with horizontal joints of the wall insulation.
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Cavity ties must be embedded to a depth of at least 50mm in the mortar joints of each leaf. Single wire type ties bent into 'Z' profiles with central 'dished' drips as well as crimped wire ties should not be used.
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Acceptable wall tie types for cavity widths not exceeding 75 mm (width of ISOBOARD® and residual cavity, if present) are: Butterfly; Modified PWD; Double Triangle; Vertical Twist
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In instances where cavity walls exceed 75 mm in width, only vertical twist ties should be used. Material used to make up these ties must have a stiffness equivalent to a steel strip 20 mm wide and 4 mm thick.
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Additional ties are required at vertical spacing, not exceeding 300 mm, near the sides of openings and at discontinuities in the masonry such as at doors, windows and control joints.
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Boards must be secured against the inner leaf of the wall with the shiplap joint arranged to shed water away from the inner leaf.
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Debris and mortar should be removed from the cavity and mortar should be removed from the exposed edges of installed boards.
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The spacing of wall ties for various widths are detailed in SABS 0164 (Table 7).
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Boards must be tightly interlocked with no gaps occurring at the top and bottom of the wall, at the building corners and around windows and other openings.
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After each section of leading leaf has been built, excess mortar droppings should be removed from the cavity face and mortar droppings cleaned from exposed edges of the installed board, before installation of the next run of boards.
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ISOBOARD® can be cut, using a sharp knife or fine-tooth saw, to fit around windows, doors, airbricks, etc. It is essential that cut pieces of boards completely fill the spaces for which they are intended and that no gaps are left in the insulation.
  
  
  
Isometric view showing position of boards
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ISOBOARD® attached to the inner leaf of a north facing double cavity wall.