What does Insulation do?
Insulation helps keeps areas of heat and cold separated. Your chilly bin is great for keeping items cold as it has polystyrene insulation. House insulation in places with hot climates keeps the house cool when it is hot outside. In Dunedin we don’t tend to have houses overheating. So house insulation is installed to keep heat inside houses when it is cold outside.
Insulation by itself does not make a house warm. For a house to be warm it needs to be heated. The insulation is there to help keep the house warm when the house has been heated.
There are varying diagrams available showing different values for how heat is lost from buildings. These diagrams shows heat loss values as provided by BRANZ for an uninsulated house and an insulated house.
With an uninsulated house it is usually possible to insulate the ceiling (unless there is inadequate access). If there is adequate access to the sub floor area then that area can also be insulated. However wall insulation is not as easy to insulate as either the inside wall linings or outside wall claddings have to be removed to install the insulation.
Up until 1978 New Zealand houses did not need to be insulated. So if your flat was built before this date then it probably does not have any wall insulation. Many people don’t realise that they are living in flats that were built 100 years ago. For example most of the houses on Castle Street are of that age. Back in those days the houses were heated all day every day as the coal range was the only way to cook food and heat water as there was no electricity (but there was a long drop toilet in the back yard).
So if you are in an old flat it may not have wall insulation but if it has access to the ceiling space and to the sub floor area then it will have had insulation retrofitted since it was built (enforced by the government). Check the insulation statement in your lease to see what insulation is in your flat.