Roof insulation: According to the House Condition Survey 2015 at least 40% of homes do not have enough ceiling insulation and over 50% of homes do not have any insulation under the floor.
Health and safety moment: For this question, you may want to look into any accessible roof spaces. Here are some helpful suggestions to keep you safe while you’re looking in there. See this PDF, Appendix B3.3.2
Roof insulation - what to look for
You can usually get access to your roof space through a ceiling hatch, either in the hall or living room (if not there, check in the bedroom wardrobes). If you have a ceiling hatch, safely peer into the roof space from a ladder and assess whether you have any insulation present. Take a tape measure with you and measure how thick it is.
Some homes do not have a ceiling hatch, either because one hasn't been installed or, more commonly, because the roof is a skillion or cathedral roof. Skillion and cathedral roofs are commonly pitched roofs in which the sloping roof is seen from the inside of the house as well as the outside. This means there is no large ceiling cavity.
Roofs without ceiling access should be assumed to be insulated if they were built after 1978. Any inaccessible roofs built before this date probably don't have any insulation.
Example of good ceiling insulation. The insulation is laid over the joists.
Example of a cathedral roof. These are frequently not insulated in older homes but should be insulated in homes that were built after 1978.
Why having roof insulation is important
According to the House Condition Survey 2015 at least 40% of homes do not have enough roof insulation and over 50% of homes do not have any insulation under the floor.
Insulation is the cheapest form of heating. A $4,000 investment in roof and underfloor insulation will pay for itself many times over the lifetime of the home and will give immediate benefits in comfort and health for the household.
The Building Code requires all new homes to have insulation in roofing, walls and floors, as well as having double glazing. But more than 600,000 existing homes are uninsulated, and 200,000 more have minimal insulation. This is a huge opportunity to lower power bills and greenhouse gas emissions from home heating and reduce hospitalisation and time off work or school due to sickness directly caused by cold, damp homes.
The first areas to insulate are ceilings and under suspended floors because it is easy and cost-effective in many homes. As of 1 July 2019, all private rental properties need ceiling and underfloor insulation wherever practical. With landlords now facing fines if they don’t do so, subsidies are now being shifted to homeowners on low incomes. For more information, see Gen Less Funding for Insulation.