Sheriff Wyllie Robertson also imposed a two-year extension on John Hoggan in order to "protect the public" on his release and banned him from contacting Tara Singh, the target of his attack, for eight years.
Stirling Sheriff Court heard Hoggan drained petrol from a garden strimmer and poured it into an empty vodka bottle and then doused a rag in petrol and stuffed it through the letter box of the three men whose house was just minutes from his home in Alloa, Clackmannanshire.
The occupants only managed to escape because Mr Singh woke up and realised the house was filling with flames and smoke.
A jury heard that jobless Hoggan, 53, had a grudge against the 38-year-old, known as Tony, because his former girlfriend, a vulnerable adult, had dumped him for the younger man.
Hoggan denied endangering the men's lives by wilful fireraising with malice aforethought, but a jury took less than an hour and a half to find him guilty by majority after a four-day trial.