Article is written to assess owner’s desires to improve historical buildings and environment functionality and it`s possible influence on historical environment in total. To plan and develop historical centre of particular town – Kuldiga – in the way “nowadays needs satisfaction does not affect needs to be satisfied for next generations” [1], sustainable planning principles has to be considered. Aims of sustainable environment are: preservation of cultural heritage, rational exploitation of buildings, improvement of public space, promotion of cultural interaction and integration of society, improvement of living space and conditions. There are three dimensions for sustainable environment – economical, social and environmental -, and its development has to be planned in balance. [1] The development strategy of Kuldiga is “… to preserve its unique cultural heritage – complex of old town and nature…” says in town development program [2]. At the same time balance between environment and cultural heritage preservation and economical development of territory is needed. Although cultural environment, cultural landscape is perceived as important value in planning preservation activities, however requirements of nowadays society determines necessity of functional elaborations of historical buildings and town environment in general. To preserve the values for long time that inhabitants, specialists and tourists mentioned, sustainable development has to be considered and first of all values has to be defined then most important functional elaborations that would allow society to live comfortably in historical environment and after that - borderlines has to be set to find the possibilities to implement. There are examples analyzed about improvements of Kuldiga old town buildings: improvement of energy efficiency, extension of buildings, building of roof store etc. in the article. There is evaluation of Kuldiga inhabitant`s survey about values of old town and their understanding about them, about right renovation and necessity to preserve in the article. Kuldiga cultural environment is analyzed and defined its values from point of view of author. Question about architect`s ethical and professional responsibility is touched, when the planning is done in historical environment.