The world is betting on a more sustainable development and it is clear that architecture is part of that bet. There are more and more concepts that set the trend in 21st century architecture: energy efficiency, sustainability, Passive House, LEED, BREEAM, almost zero building, geothermal, heat pumps, energy self-consumption, etc. We are increasingly supercharged with information about these concepts, especially based on forums and social media news. However, this trend needs a solid, qualified and critical base, since there is a risk that all this bet will become a "sales fad" and not a tool to improve the quality of life of the users of our services, buildings and cities.

The Environmental Conditioning II subject taught in the degree of architecture of the University of the Basque Country until now focused on the design and evaluation of the thermal part of the projects to meet the minimum requirements of the current regulations. And from this envelope design, calculate energy demand and energy certification. However, from the University we must be aware that the students must be prepared and trained to meet the needs of the agents related to the construction sector. And one of the key trends demanded by some agents (Europe, Spain and the Basque Country) is construction according to the Passive House standard.

Among other things, this trend considerably increases the degree of thermal isolation required by the current regulations, which directly affects various aspects of the architecture, from the design of the detail of the construction, to the thermal behaviour of the building and the economic cost. The information published by many architects and construction industry technicians in different forums (networks, media, forums or congresses) highlights the advantages associated with this standard. However, other scientists have questioned the benefit of this stamp with regard to the current regulation in the climate areas of Spain.

In view of this scenario, the aim of this course is for students to acquire the skills associated with this subject and, above all, for them to have the criteria and knowledge to deal with this invasion of less objective information.

To do this, since the course 2023/24, the teaching team of this subject has proposed to analyse the same building but with two different envelopes, the first one with thermal performances that are limited to comply with the existing regulations and a second scenario, where the building envelope is adapted to the Passive House standard.

This evaluation of the two scenarios will allow answering the following questions:
- How much annual environmental and economic impacts are reduced compared to Passive House standards and the current regulation?
- What is the economic return or return of the economic overrun associated with the Passive House building with regard to the current regulation building?

In order to carry out this work, the methodology of problem-based learning (PBL) has been followed, a teaching technique based on self-learning and the development of critical thinking. Each group has worked on four projects, which will allow identifying, calculating and discussing about the two questions previously defined.

Keywords: Critical spirit among architecture students, Passive House, current regulation, problem-based learning (PBL).