The paper aims to assess the energy performance of a thermal rehabilitated ground floor building by using new thermal insulation panels with double-side anti-condensation foil on the exterior and polyurethane foam or polyisocyanurate on the interior (PUR or PIR) in various ways. The study also wants to emphasize the benefits of using these insulating materials encouraging their further use. Therefore, five scenarios are carried out, four thermal rehabilitation scenarios and the reference building scenario, without thermal insulation. The obtained results are evaluated by comparison. The results point out the energy performance of PUR and PIR used as thermal insulation panels for the building envelope but also the economic impact and the economic efficiency that involves using such panels. This work is based on the energy efficiency requirements targeting the building envelope and takes into account mainly the behavior of the envelope elements while the heating system is treated in a simplified manner, considering its usual efficiency. The conclusions highlight the main advantages of using these panels for buildings thermal rehabilitation compared to other common materials, such as polystyrene or mineral wool.