An intellectually disabled man has been sentenced to five years prison for arson, in what a Tasmanian judge has described as a difficult sentencing decision.

Bevan William Parkinson has more than 100 prior convictions.

He pleaded guilty to setting fire to his Housing Tasmania unit at New Norfolk in 2012.

The fire caused $90,000 worth of damage.

He told investigators he enjoyed the fire and was not sorry.

Defence lawyer Roshelle Mannering told the Supreme Court, Parkinson did not commit offences with malice or intent.

Ms Mannering said her client found security and stability in prison, and was known to commit crimes so he could return to incarceration.

Judge Stephen Estcourt said while the sentence was not a deterrent for the offender, Parkinson was uncontainable in the community.

Parkinson will be eligible for parole after serving three and a half years.