Assistant Fire Chief Chris Cachat said when firefighters arrived at 79 Greenridge Drive around 5 a.m. they found the garage engulfed in flames and spreading to a sunporch to the rear of the single-story home.
Firefighters quickly contained the flames before they reached the main portion of the ranch-style house.
Cachat said the homeowner and lone occupant, Kathleen Dunn, awoke to a popping sound, saw the fire, and called 911. She escaped unharmed.
The state Fire Marshal Office and Dalton Fire Chief Richard Kardasen are jointly investigating the cause of the blaze.
"The fire has been deemed suspicious," said Cachat who cautioned that does not necessarily mean a criminal act has been committed.
He added, the house remains structurally sound and livable, but the sunporch was heavily damaged.
Pittsfield and Hinsdale Fire Departments assisted Dalton in fighting the fire.