Resumen
The increased number of energy efficiency requirements of the European Union has increased the renovation rate of apartment buildings. The external thermal insulation composite system (ETICS) is often used to upgrade the façade. However, the construction process shortcomings very often cause defects shortly after completion. This paper develops a technical–economic relevance assessment model of the onsite degradation factors for better quality assurance in an SME. The model quantifies the technical significance of the degradation factors along with the future repair costs. The technical severity of 103 factors is evaluated by 12 experts, and the data is validated with the Friedman’s test. The occurrence ratio, detectability, and latency period are foreseen by five experts and validated with the Delphi technique. The results of the three sample simulations emphasize the activities during substrate preparation and application of adhesive as well as a base coat with reinforcement mesh. The application of a finishing coat and installation of insulation plates have less relevance. It is recommended to upskill the craftsmen in regard to working with mixtures as the shortcomings are covered simultaneously and the failure detection period is short. The measures to protect against external weather effects are recommended due to their relatively high impact. Half of the shortcomings appear during the first two years.