Statistical analysis of about 1,300 ductwork airtightness measurements in new French buildings: impacts of the type of ducts and ventilation systems

This paper summarizes the most recent results of the French database of ductwork airtightness. This database was created in 2016. It is fed through measurements performed by qualified testers according to a national scheme regarding ductwork. Measurements are mainly performed in building applying for the Effinergie + label which requires class A for ductwork airtightness. Therefore, results discuss in this paper only apply to the buildings of the database and cannot be generalized to all new buildings in France. The database was enriched in 2017 by new measurements, making the total number of measurements around 1300. This enables new analyses regarding the ductwork characteristics and its impact on ductwork airtightness.    
First, this paper summarizes the recent results regarding main characteristics of the buildings and ventilation systems. Then, the paper analyses the measurement results regarding ductwork airtightness classes depending on several factors, in particular building’s use, type of ventilation system, targeted class and the type of ducts.  
The results show that the number of measurements increases annually in both residential buildings and non-residential buildings. In particular, measurements in residential buildings are growing fast. In 2016, they represent 73% of the total measurements. Regarding ventilation system, residential buildings, are mainly equipped with single-exhaust ventilation systems (80%), whereas a large part of non-residential buildings (84%) are equipped with balanced ventilation systems.  
Regarding the type of ducts, flexible ducts are widely used in single dwellings in association with single-exhaust ventilation system (89%). Rigid metallic ducts are mostly used in multi-family and non-residential buildings in association with both single-exhaust and balanced ventilation systems respectively (around 90% for both). Regarding ductwork airtightness performance, it seems to be related to the ventilation system and especially to the type of ducts. Class A is the most frequent result for residential buildings, which are mainly equipped with single-exhaust ventilation system. However, in single dwellings where flexible ducts are mostly used, 55% of measurements achieved Class A or better, against 77% in multi-family buildings with a large part of rigid metallic ducts. In non-residential buildings mainly equipped with a balanced ventilation system and rigid metallic ducts, class B is the most frequent result, and 90% of measurements achieved Class A or better.