Reduction of energy consumption and green house gas emissions of buildings is a great challenge in Europe. In this context French energy performance regulation, RT2012, requires an improvement of the buildings' airtightness. In airtight buildings, ventilation must be perfectly controlled to ensure good indoor air quality. However, many failures are observed when ventilation systems are inspected (Jobert, 2012). They are mainly due to bad conception, poor implementation and lack of maintenance. Most of the time, dysfunction leads to a reduction of the ventilation flowrates and to poor indoor air quality.
To improve the ventilation systems' reliability, French energy label “Effinergie +” imposes the ductwork airtightness to be at least Class A. This leads to various issues regarding ductwork airtightness:
- What is the impact of each component of a ductwork on the leakage rate? Is good airtightness reachable with existing products?
- What is the impact of airtightness on ventilation flowrate and fan energy consumption?
- Are ductwork pressurization tests reliable? Do the position of the measurement devices, leakage distribution and ductwork pressure drop have an impact on the result of the test?
To answer those questions a full-scale exhaust ductwork of multi-family building was set in our laboratory. The impact of each components of the ductwork (rigid, circular GALVA) was tested. Holes were then drilled in the ductwork to vary airtightness.
Our study showed that:
- Even with good implementation it is difficult to reach class C for ductwork airtightness because of some leaky components in the ductwork;
- A decrease of the airtightness (from class C to 1,6*class A) may either reduce flowrates by 10% at the air terminal devices or increase the energy consumption of the fan by 10 to 40% ;
- Neither the position of the fan, nor the leakage distribution, nor the pressure drop has an impact on the result of the airtightness test (at class C and 1,6*class A).