To draw attention to possible refurbishment options of box type windows the present work aims to scientifically compare different refurbishment methods regarding their impact on airtightness. Technical interventions ranged from fundamental maintenance to application of gaskets, renewal of putty and fittings to the production and installation of new sashes. This way, small actions were implemented before major ones. Additional field tests with blower door measurements were conducted at three different locations examining a total of 14 windows across 7 rooms. Findings showed that a considerable decrease in air loss could be achieved with relatively simple interventions. In both test series, gaskets had a considerable positive impact on airtightness. It has to be noted that in the context of retrofitting window sealings it is important not to neglect hygric aspects. Other refurbishment options like simple maintenance and implementation of new putty also increased airtightness. In general, the results point out the possibility of box-type window refurbishment in order to preserve them.