Overall, fibreglass insulation is the cheapest and most effective insulation option available, making it a popular choice for homeowners and builders alike.

The cheapest method for a DIYer is to roll out unfaced fiberglass insulation over any existing insulation. We don't know what you have now, "R" value or type. That would be a helpful factor in determining how much more you should add. Standard fiberglass blanket insulation adds between 3.2 to 3.4 "R" per inch.

Cost to Insulate a House in Melbourne, Adelaide and Sydney 5 or higher is recommended for walls. Cost estimates for insulating a 100m2 ceiling range from $1,800 to $2,500 including materials and labour. Insulating the walls in a 3 bedroom house may cost $3,000 to $5,000.