This report examines different types of window renovation optionsfrom an environmental and economical standpoint, with the purpose towiden the decision basis of the housing cooperative Utsikten, which’sreal estate is the subject of investigation in this report, and toenable corresponding investigations of similar real estates throughthe creation of a simplified calculation tool. The investigatedscenarios in the report are, apart from the reference case, changingthe windows to three glass windows, installation of an internalinsulation window, and replacing the inner glass of the existingwindow to insulation glass.Two calculation models were constructed, one with energy data fromthe simulation program VIP-energy. The other, simplified version withenergy data calculated from the windows U-value. Environmental datawas collected for installation of the different scenarios, transport,and energy consumption. Economy data was collected for installation,maintenance, and energy prices. All data was put together in thecalculation models and the results got compared.The calculations show that changing the windows to three glasswindows is the most economical alternative. It’s also the mostenvironmentally friendly option when data for Uppsala’s districtheating is used. If data for “district heating with high proportionrenewable“ is used, installation of an internal insulation window isthe most environmentally friendly option. Uncertainties about theresults are discussed in the report.