Statistical analyses of about 420,000 measurements of the French database of building airtightness

Purpose of the work
The French database of building airtightness has been fed by measurements performed by qualified testers since 2006. The database is enlarged each year by more than 65,000 measurements since 2016, making the total number of measurements about 420,000 at the end of 2018. This work presents a statistical analyses of the French database of building airtightness.
Method of approach
Currently, more than 420,000 measurements have been recorded in the database. It includes all the measurements that were performed by certified testers till the end of 2018. Statistical analyses of the database are carried out using:

1. boxplots and histograms to summarise the main descriptive statistics;
2. and one-sided paired t-test to analyze the statistical significance of differences in the mean air leakage rates.

Content of the contribution
After a brief introduction regarding the French context of building air permeability, the contribution gives an overview of the database followed by a detailed presentation of the results including:

1. impact of buildings’ characteristics (building area, main material, ventilation system, insulation...) on building airtightness level;
2. the evolution of the air permeability (French indicator q4Pa-Surf, and n50) in new and renovated buildings depending on the building use (single-family houses, multi-family buildings and non residential buildings);
3. the frequency of detected leakages and their impact on the air leakage rate.

Results and assessment of their significance
Almost all of the measured new residential buildings meet the Energy Performance requirement imposed by the French Regulation RT2012 (93 % for single dwellings and 98 % for multi-family buildings).
As there is no requirements for non-residential buildings, much less are tested. However, the air permeability is gradually improving, with average values in 2018 clearly below the mandatory threshold for multi-family buildings. There is also no mandatory requirement for renovated buildings (both residential and non-residential). Very few measurements are therefore available for renovated buildings. Results show an improvement of airtightness in single dwellings and nonresidential buildings before and after renovation. However, there is no improvement in retrofitted multi-family buildings.
The analysis of the detected leakages shows frequent leakages through doors and windows, penetrations through the envelope and electrical components. However the most critical leakages are not always the most frequent leakages, e.g. the air permeability can be significantly increased in case of leakages at the junction between the floor and the exterior walls in multi-family buildings, and leakages through suspended ceiling in non-residential buildings.

For further information please contact Bassam Moujalled at: bassam.moujalled@cerema.fr