In order to establish the effect of replacing mortar joints by plastic or elastic sealants, an investigation of a number of multistory buildings has been carried out within the framework of the Danish Energy Research Programme EFP-81. An actual heat-saving effect could be established only in a few cases after replacement of windows and joints. The condition of the sealants was good after a few years of practical exposure. A surface cracking wich was not found to have any significant importance to the life of the joints was noted. The adhesion was good to tiles, wood and PVC. It was not possible to establish any decomposition of wooden windows owing to formation of condensate behind the tight seaplants placed at the outside, i.e. as a one-stage joint. It must be underlined that the investigation has only comprised brick built buildings.