Michael Hill died as a result of smoke inhalation in the blaze at his home in Brentwood Avenue, Bamford, on May 10.
The retired welder’s inquest was held at Chesterfield Coroner’s Court on Tuesday.
Matthew Kewley, assistant coroner, said: “The fire investigator identified that the origin of the fire was a seat on a two seater sofa in the lounge.
“There were a number of combustible materials located in the origin of the fire including books and paperwork.
“The most likely cause of the fire was naked flame ignition of these combustible materials.
“However, it was not possible to determine whether this was a deliberate or accidental ignition of the combustible materials.
“The fire investigator was able to rule out all other causes of ignition such as electrical causes.”
Mr Kewley recorded a narrative conclusion.
Visit www.derbys-fire.gov.uk/safety for fire safety advice.