Born in Schäßburg in Austria-Hungary (today Sighişoara in Romania), Grünanger studied at the Academy of Fine Arts Vienna architecture school between 1877 and 1879, under Friedrich von Schmidt. As a style, he was a representative of the late historism, of the eclectic style, the Viennese Neo-Baroque and the Vienna Secession.
In 1879, he was appointed in the Direction of Public Buildings, part of the Bulgarian Ministry of Internal Affairs, and became Chief Architect of Razgrad, later court architect of Knyaz Alexander of Bulgaria and his successor Ferdinand. During his thirty years of work in Bulgaria, he designed and constructed numerous remarkable public and residential buildings, mainly in Sofia. In 1908 he returned to Austria-Hungary and retired in Salzburg, but briefly returned to Bulgaria between 1911 and 1914 until his work in the country was discontinued after World War I.