Mankind strives for accomplishing the mutually agreed goals in Agenda 2030 where the thirteenth goal is to stop climate change. The amount of sand used in several materials is of great importance to the environment. Sand is a crucial component when producing flat glass, and one way of decreasing the construction sectors impact on the climate change is recycling of old flat glass. The study investigates the potential for an easier reuse of flat glass. The purpose of the thesis is to increase the reuse of flat glass and thereby reduce the climate impact from the construction sector. The aim is to bring forth a crosslist for reuse of flat glass, to find out if the bending strength in an old glass can achieve the requirements of today's standards and to make an overall calculation of the costs andthe enviromental savings when reusing flatglass. Several methods were used to achieve the aim, namely a literature study to gather information, dialogues that give a range of how different aspects can be valued and abending strength test that show the reused flatglass´s ability to withstand external pressure. The overall costs and the enviromental impact were also calculated. The result shows that the crosslist encounters for the properties being fulfilled in a reused window, given that the performer has a certain knowledge. The bending strength test showed that the roughly 60 year old flat glass did achieve the requirements and can therefore be used as a product in a new building. The dialouges enlighted the greatest obstacles for reusing flat glass as lack of knowledge and supply. More specific problems while using old flat glass is the matters of energy and guarantee which are essential when deciding if reuse is possible and is problematic for whoever tries to upgrade a window that is not reaching its specified requirements. The requirements if a window is to be reused or not in a specific way is a part of thecrosslist where the properties are categorized from 1 to 3 where 3 has the lowest performance but still achieves the minimum requirements. The possibly changed strength of the tested flat glass in terms of age is difficult to assess as there is no new reference object with a similar thickness to compare with. The overall calculations of costs and environmental impact shows that large savings can be made . The study show the possibilities of how a flat glass can be made by reusin flat glass. Nonetheless, more deep diving studies need to be deducted within the area but perhaps in the long term the study may contribute to increasing the reuse of flatglass.