A former insulation installer has told a Royal Commission hearing in Brisbane that he lost millions of dollars in the former Rudd Government's home insulation program.

Dozens of insulation businesses that existed before the program are being represented at the Commission.

Greg Rashleigh worked in the industry for more than 30 years and was the director of Toowoomba's All Seasons Insulation.

He said he attended a meeting when then-minister Peter Garrett promised the scheme would run full-term.

Mr Rashleigh said he spent more than $2 million on a new manufacturing mill in 2009 to keep up with expected demand.

But the scheme was terminated within months and the mill never opened.

Mr Rashleigh said that left him with months worth of advance orders that "nobody wanted any more" and more than $3 million worth of stock that was "still sitting there now".

He received Government compensation for 15 per cent of the stock, but nothing for his investment in the mill.