I suggest everyone should have a read of this publication dated 20th July 2011.
Australian Building Codes Board - Condensation in Buildings
http://www.abcb.gov.au/index.cfm?objectid=49833C4B-B29A-11E0-8548001143D4D594
Raised quite a few issues that many may not be aware of that can create problems.
Includes case studies of retrofitted insulation that caused problems in a skillion roof, extra insulation in a high roof ceiling, and a new build in Victoria's fire zone as a new home to replace a lost one - that created condensation issues.
It's a good publication and one that anyone planning on doing a retro fit of insulation should consider as a MUST READ to make you aware of issues you could potentially create whilst trying to do good in your home.
Includes details on walls, floors and ceilings and condensation issues that can be caused / created by not insulating the area correctly, using the wrong type of vapour barrier or putting them on wrong side of the wall / roof / ceiling / under floor.
Includes details on installing insulation in temperate, cold and tropical regions