Building and ductwork airtightness represent a key challenge towards nearly zero energy buildings and deep energy retrofits, and therefore towards the ambitious targets set in the climate action plans of many countries to substantially reduce greenhouse gas emissions and move towards a climate neutral building stock. Results of the EU ASIEPI project (www.asiepi.eu, ) have shown that for most European climates, leaky envelopes and duct systems have a severe impact on the total energy use of the building, e.g., on the order of 10 kWh per m2 of floor area per year for the heating needs in a moderately cold region (2500 degree-days) and 0 to 5 kWh/m2/year for the ducts plus the additional fan energy use . Many countries have made progress in achieving airtightness levels in new buildings during recent years in many countries. However, a continued attention to building airtightness is necessary specifically for the existing building stock., All experiences related to these challenges are worth sharing to accelerate the market transformation needed on these issues .
Challenges for the building stock
The EPBD  sets ambitious targets towards zero-emission buildings with continued obligations for EU countries to implement regulations to increase the number of nearly zero-energy buildings (NZEB), and to generalize nearly zero-energy targets in new buildings and deep and major renovations. Therefore, as illustrated in the Figure:
- A continued attention to building and ductwork airtightness is necessary specifically for the existing building stock. (1);
- As a result of the increased emphasis on health and well-being (2), and greenhouse gas emission reduction (3), the need for appropriate, energy efficient, ventilation systems will continue to grow. Issues include correct airflow rates, air quality, acoustics, draught, comfort, energy optimisation, energy recovery, coupling between ventilation and other HVAC functions (e.g., heating, domestic hot water production), use of ventilation systems for avoiding high internal temperatures, and economics. These issues have to be handled at a large scale. A specific challenge is to identify and install ventilation systems that are suited for advanced energy retrofits and improve IAQ in an energy efficient way.
- Indirectly, the move towards zero emission buildings will lead to a greater need for ventilation systems, whether mechanical, natural or hybrid (3). Smart control of ventilation systems becomes increasingly important to adjust the systems to indoor climate needs, minimize energy use, and provide flexibility to electricity grid operation.
- Overheating is an issue of concern in new buildings in many countries. With continued climate change, the probability of overheating will increase. Ventilative cooling and other resilient cooling strategies will gain in importance for new and existing buildings.
- As a result, the expression already from the 1980s, i.e. ‘Build Tight – Ventilate Right’ is still valid and it remains a major challenge for the existing building stock (4).
What is TightVent Europe?
Since there are to a rather large extent similar challenges for the whole of Europe, the TightVent Europe platform aims at meeting the obvious need for a strong and concerted initiative to overcome these challenges. Indeed, sharing experience on practical issues such as specifications, design, execution, control, … and taking advantage of the lessons learnt from pioneering work will help improve airtightness quality while keeping in mind the need for adequate ventilation.
TightVent Europe has been initiated by INIVE EEIG (International Network for Information on Ventilation and Energy Performance) with the financial and technical support of the following founding partners: Building Performance Institute Europe, European Climate Foundation, Eurima, Lindab, Soudal, Tremco illbruck, and Wienerberger. Since November 2011, Acin Instrumenten, BlowerDoor GmbH, dooApp, gonal, Mez-Technik, Retrotec and SIGA have joined TightVent and thereby bring air leakage measurement expertise to the consortium (more information).
All partners are strongly interested in setting up a European wide collaboration and using the knowledge gathered through TightVent Europe for raising the awareness among all building professionals, for developing improved training courses, and for helping professionals in the development of quality management approaches. The partners also believe that there are areas that need further investigation (for example, the durability of seals, the integration of airtightness and ventilation issues in renovation projects, the variability of the energy impact with climate, etc.) where TightVent Europe can play a major role both in terms of research development and dissemination.
The target audience of the TightVent Europe activities is wide and ranges from the research community over designers, practitioners, supply industry to European, national and regional government policy makers. It includes:
- Policy makers
- Training centres (front-runners and associations/networks)
- Designers, engineers and builders, air leakage testers (front-runners and associations/networks)
- Research and technical centres
It is clear that awareness raising is a key element, as is the development of appropriate support tools and getting the knowledge into the market.
 Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast). Official Journal of the European Union. 18 June 2010. L 153/13-34.
 Carrié, F.R., Andersson, J., and Wouters, P. 1999. Improving Ductwork – A Time for Tighter Air Distribution Systems, Report, EU Project SAVE-DUCT, Brussels 1999. ISBN 1902177104.
 Carrié, F.R., Rosenthal, B. 2008. An overview of national trends in envelope and ductwork airtightness, AIVC Information Paper VIP 29, August 2008, 6 pp.
 Carrié, F.R., Wouters, P., Heijmans, N., Rosenthal, B., Aurlien, T., Guyot, G., 2008. Ways to stimulate a market transformation of envelope airtightness. Analysis of on-going developments and success stories in 4 European countries, Web event, 12th December 2008
 Malmström, T.G., Andersson, J., Carrié, F.R., Wouters, P., and Demotte, C. 2002. Source Book for Efficient Ductwork in Europe. Report, EU Project SAVE-AIRWAYS, Contract n° 4.1031/Z/99-158. 2002.
 Publications and activities of the ASIEPI project. EU Project IEE-SAVE, Contract n° EIE/07/169/SI2.466278.
 Roulet, C.A., and Vandaele, L. 1991. Air Flow Patterns within Buildings Measurement Techniques. AIVC Technical Note 34, 284 pp. Available at www.aivc.org.
 Schild, P., Caillou, S., Millet, J-R., Mattsson, L. Å., Railio, J., Carrié, F.R. 2009. How to improve ductwork airtightness – Ongoing developments and success stories in Europe, Web event, 16th December 2009
 Schild, P.G. and Railio, J. 2011. Airtight ductwork – The Scandinavian success story. REHVA Journal, March 2011, pp. 26-29.
 Schild, P.G., and Mysen, M. 2009. Recommendations on Specific Fan Power and Fan System Efficiency, AIVC Technical Note 65, 42 pp. Available at www.aivc.org.
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