Below is the easiest and cheapest method of making your own insulation.
DISCLAIMER :-this process creates hydrogen as a by product, please offset this by planting some trees and or greenery around your work space. As with anything do your own research and take into consideration your own and others personal health and safety.

Aerated concrete or ‘aircrete’ block
First produced in Sweden in 1923 and used in the UK since the 1960s (when they were known as ‘cellular’ or ‘gas’ concrete blocks), aerated concrete or ‘aircrete’ blocks are the lightest of the family of concrete blocks. Aerated blocks are distinguished by their capacity to perform a dual structural / insulation function. Though limited to structural applications in low-rise construction and partitions as well as a component of curtain walling in higher buildings, aerated blocks can perform a similar range of functions as dense and lightweight blocks. The blocks are made from cement, lime, sand, pulverised fuel ash (PFA) and water. PFA is mixed with sand and water to form a slurry. This is then heated before being mixed with cement, lime and a small amount of aluminium sulphate powder. The aluminium reacts with the lime to form bubbles of hydrogen. As the mixture expands into a ‘cake’ the hydrogen is diffused and replaced by air. When the mixture is partially set, it is cut to block size and transferred to an autoclave where it is high pressure steam-cured to develop strength.

• Typical thermal conductivity: 0.09 – 0.20 W/mK

Pro Moderate thermal mass
Pro Uses industrial waste (PFA) as a prime constituent
Pro Very good insulating properties
Pro Based on volume, aerated blocks contain around 25% less embodied energy than other concrete blocks
Pro Good workability
Pro Lighter weight saves energy in transportation
Pro Reasonable sound absorption properties
Pro Reusable if dismantled carefully, particularly if lime mortar has been used
Con Non-renewable materials
Con Prone to impact damage
Con Use of aluminium adds embodied carbon
Con Use of cement contributes to global warming

http://www.greenspec.co.uk/building-design/blocks/