Polyurethane (PU) is the sixth most used polymer worldwide, with an annual production of around 18 million tons. Its commercial success, however, has led to significant waste generation. Historically, landfilling was the primary disposal route, but chemical recycling has emerged as a sustainable alternative. Among chemical recycling strategies, re-monomerization via solvolysis stands out for PU waste streams, especially when contamination is high, or virgin-like product quality is required. Glycolysis, employing diethylene glycol, is the most prominent process due to its relatively high-boiling solvent, facilitating reaction temperatures of 160–250 °C under atmospheric pressure. The recovered polyols can be separated from the reaction mixture and reused in new PU synthesis. Despite this potential, PU recycling rates remain low, partly because of the polymer’s diverse forms and customized formulations (e.g., flexible or rigid foams, elastomers). The main goal of this study is to develop a cost-effective approach for transforming post-consumer PU into valuable raw materials. The strategy involves using various pretreatment methods to modify PU waste, enhancing its susceptibility to solvolytic cleavage. In particular, the focus in the current stage of research was on rigid foams derived from commercial polyols and methylene diphenyl diisocyanate (MDI) polyisocyanates. Pretreatment was applied to produce a homogenous stream with increased surface area and reduced granulometry and glycolysis followed under mild conditions to break down PU into oligomers with added value. The recovered materials were then upcycled demonstrating potential for closed- or open-loop applications; regarding the latter, properly adapted formulations were developed to utilize the recovered materials for the production of construction products, such as waterproof coatings.