The body of the man in his 70s, was found at the house in Nettleden Road, Little Gaddesden, near Berkhamsted, on Saturday afternoon.
A man in his 80s was also taken to hospital, a police spokeswoman said.
Detectives want to question 55-year-old Ian John McLoughlin, also known as Ian John Baker, and have warned people not to approach him.
Det Ch Insp Martin Brunning, from the Bedfordshire, Cambridgeshire and Hertfordshire major crime unit, said: "The investigation is still in its early stages.
"However, we are continuing to treat the death as murder. We urgently want to speak to Ian McLoughlin in connection with this offence."
He is described as white, about 6ft (1.8m) tall, with straight, greying, collar-length hair and of average build.
He is believed to have been wearing sunglasses, blue jeans or three-quarter length trousers and a dark blue, light blue and white checked short-sleeved shirt with a button-down collar.
Anyone with information has been urged to contact police or Crimestoppers.
Officers have been conducting additional patrols in the area to provide reassurance to residents.
Police are seeking a man over the murder of an elderly man found dead at a house in Hertfordshire.