As urbanization continues and more people move into cities and urban areas, pressure on availablelandfornewconstructionswillcontinuetoincrease. Thissituationconstitutesanincentiveto reviewtheneedforinteriorspaceandusesofexistingbuildings. Agreatdealcanbegainedfromusing existingbuildingsmoreefficientlyinsteadofconstructingnewones: Reducedresourceusageduring construction(investments,naturalresources,andenergy),operation,andmaintenance;moreactivityper squaremeterofbuildingscreatesagreaterbasisforpublictransportandotherservices;moreintensive useofbuildingscreatesamorevibrantcitywithoutbuildingonvirginland. Theaimofthispaperisto initiateadiscussionregardinghowdigitalizationcanaffectthedemandandsupplyofinteriorspace in existing buildings and elaborate on how policy can support more resource-efficient uses of space. New activity-based resource measurements intended for use in buildings are proposed, and several principles that have the potential to decrease environmental impact through more efficient usage of space are outlined. Based on these ideas for encouraging the flexible use of building spaces that are facilitatedbydigitalizationandthenewmeasurementapproaches,afour-stepprincipleforconstruction isproposed: Thefirststepistoreducethedemandforspace,thesecondistointensifyusageofexisting space, the third is to reconstruct and adapt existing buildings to current needs, and the fourth is to constructnewbuildings. Urgingpolitical,municipal,construction,andreal-estatedecisionmakersto contemplatethisprinciple,particularlyinviewofthenewconditionsthatdigitalizationentails,willlead tomoresustainableconstructionand,inthelongterm,asustainablebuiltenvironment.