Potentials and limitations for energy refurbishment of multi-family residential buildings built in Belgrade before the World War One

•Energy performances of pre-WWI buildings are below requirements of modern thermal regulations.•Proposed improvement measures were successful from the point of view of energy efficiency.•Small window to wall ratio contributed to less efficient effect of window replacement.•Proposed energy improvement measures are not always compatible with historic buildings.

After the new set of regulations related to the problem of energy efficiency of buildings has been adopted, energy efficiency became the primary issue of the present building practice in Serbia, referring both to new buildings and to existing ones, among which refurbishment of buildings built before the World War One requires a special attention. Multi-family houses from that time represent today about 1% of the total building stock. Rarity of the buildings of this age and their structures caused that a large number of them are listed as cultural heritage, so any intervention on them, including those which are the result of adjustment to modern needs and building rules, becomes especially sensitive and complex. In particular, this refers to energy improvement measures which, according to the new regulations, are an inevitable part of any building intervention. Having in mind all the mentioned aspects, and focussed on the relevant examples of multi-family houses from Belgrade dating before the World War One, the potentials and limitations for their energy refurbishment were investigated.