The purpose of the thesis work is to increase knowledge about older wood materials. The quality of the material and how to take care of it, restore it and reuse it, will be investigated. The aim of the report is to help reduce the amount of wood waste that the construction sector is responsible for and indicate the differences that exist between wood today and wood from the past. Due to the broad subject, there is a focus on wooden windows, which are used as examples in the report. The focus is carpentry wood andolder wood material before the middle of the 20th century.

To achieve the goal, several interviews were conducted with experts in the field as well asa case study where older windows were replaced and what the consequences of that led to. The results show that wood production and the quality of timber have changed greatly. Before the year 1950, many natural forests that existed with slow-growing trees were used and much greater emphasis was placed on the quality of the material. Today's woodproduction is dominated by fast-growing trees and the trees are treated like a "bulk product". The trees are cut down all at once and sorted by area of use, rather than its individual characteristics. With the help of technological advances, the pursuit of efficiency in production has contributed to greater financial gain. Older wood materials turned out to have a higher quality compared to today's fast-growing timber. Properties of the older wood are higher density, denser annual rings, more resistant to moisture and above all a larger amount of heartwood. On the other hand, today's fast-growing woodmaterials are faster and easier to process.

To carry out a restoration work of a window, competent craftsmen are required, of whichthere is currently a shortage. The demand for recycled wooden windows and interior doors has recently increased. Caring for older wooden windows is done by regular painting, scraping, and caulking of windows. The window replacement that wasinvestigated resulted in high costs and more emissions of carbon dioxide during the manufacture of the new windows, but energy consumption in the villa was reduced as the thermal insulation was improved.