Kühnert's most active period as an architect was in the 1920s. Most important of all works - rebuilding and renovating several buildings in the historical Old Town of Tallinn. Many of these buildings are now valued as examples of heimat style and art nouveau mixed with Estonian traditional architecture. Most of the buildings designed by Kühnert are small-scale dwellings. His 1930s creation can be categorised as functionalism. He also drew the general plans for garden cities of Merivälja (1924-1925) and Nõmme (1926-1927) (both with Robert Natus).