Extensive research studies in many countries have found gaps between the design intent and real-world operation of buildings, which often lead to much higher energy use in practice than was estimated at design stage. While the reasons for such performance gaps are varied and complex, IEA Energy in Buildings and Communities (EBC) research projects have recently been making progress in resolving them.

The current development in building energy efficiency towards nZEB buildings represents a number of new challenges to design and construction. One of these major challenges is the increased need for cooling in these highly insulated and airtight buildings, which is not only present in the summer period but also in the shoulder seasons and in offices even in midwinter. Resilient ventilative cooling can be an energy efficient solution to address this cooling challenge in buildings.

Air infiltration in buildings has multiple consequences on energy use and indoor environmental quality. Therefore, in the last 10 years many countries have introduced requirements for building airtightness in their EP-regulation. Those requirements often prescribe that a test is performed by a qualified tester and that every test performed is recorded in a database.  Hundreds of thousands of data are now available in Europe.

Various studies have shown that ductwork leakage has a major impact on energy use (i.e. increased fan energy use, heating & cooling losses etc.). However, in most European countries, it is not common to perform ductwork airtightness tests, which is probably due to the lack of awareness on the consequences of ductwork leakage. As follows, ductwork airtightness is not properly taken into account in most Energy Performance Regulations and Calculations.

Progressing the scientific basis of indoor environmental quality is essential to understand which aspects can be better optimised to substantially reduce energy use in buildings. In recent years, IEA Energy in Buildings and Communities (EBC) international research projects have been investigating for this purpose both indoor air quality and thermal comfort. The embodied impacts of buildings and their services systems are also a focus of EBC's research.