Read about the defeat of the SNP Scottish Budget from the horse's mouth.
The Scotsman sums it up like this:
Right at the end of the debate, Mr Swinney said £33 million would be provided for the scheme, insulating 100,000 houses, as Mr Harvie wanted. Although Mr Swinney guaranteed that this money would be spent, he could not give an assurance that all of it would come from the Scottish Government.
Mr Harvie was worried that some of the money might come out of budgets already earmarked for fuel poverty when he wanted it all to be new money. And it was at that point that he decided the Greens should oppose the SNP's Budget.
Caution: the quote is from a newspaper, so may be riddled with misinformation and spin.
My impression is that the SNP treated the Greens with political disdain, failing to negotiate clearly and communicate their views in good time.
In the end, any money spent on saving energy has to be a good investment, and the SNP has paid the price for their political arrogance and economic ignorance.
Update on this from the horses' mouths.