For years, ventilation and air-conditioning systems have played an increasingly important role in ensuring sufficient air exchange in buildings. With time buildings are becoming more and more airtight to avoid energy losses through uncontrolled air leakage and mechanical ventilation systems are installed to ensure a good indoor air quality. What is a good approach in theory can fail in practice due to leaky ductwork. Various studies have shown a low awareness on this issue in most European countries , with leaky ductworks impacting the energy use, the indoor air quality or generating noise .
One solution applicable both to new ductwork systems not meeting the expected air tightness class and existing leaky ductwork, is a sealing through aerosols injection. This technique explained in  and patented as the Aeroseal process, allows to seal air duct systems from the inside within a short time and without having to search for leaks beforehand. Leakages with gaps of up to 15 mm are permanently eliminated by using a sealant that is certified according to VDI 6022. In Europe almost 700 sealing projects have been carried out using this method since 2015.
This paper presents the results of 7 ductwork sealing projects performed during the year 2021 on existing (mostly non-residential) buildings located in 7 different European countries: Germany, France, Ireland, Czech Republic, the Netherlands, Poland and Switzerland. The ductwork leakages were reduced from 87% up to 98% with an average of 93%. The impact on the energy consumption is quantified for these 7 buildings. The highest savings are for the approximately 30 000 m² building in Ireland, reaching 36k€ per year for about 2/3 of the ductwork sealed.
Each sealing project being performed by a different service company, feedback from 6 operators were collected giving information on:
- Possible ductwork airtightness issues encountered on-site in the various European countries: poor workmanship; failed manual sealing; lack of air duct clamps; holes made by air tightness testing devices and flexible connections that opened up.
- Possible technical sealing issues such as leakage flowrate measurement problems below 1L/s
- Feedback from costumers: decreased energy consumption; improved IAQ; less leakage of toxic gasses and odor disappearance
- Some trends regarding the market of ductwork sealing in their country, for example in Ireland more stringent criteria for pressure testing of systems result in more duct tightening work.