Adequate ventilation as well as good envelope and ductwork airtightness represent a specific challenge for new or renovated nearly zero-energy buildings. Alone, they can represent over 50% of a building's total space heating (or cooling) needs, and their share often increases with increasing energy performance.

This is the reason why many issues have arisen in the past few years regarding regulatory and voluntary initiatives to improve envelope and ductwork airtightness, bringing forward apparently simple questions such as:

• Should there be specific airtightness requirements? If so, should they be differentiated with climate, building usage, and ventilation system type?
• Should there be a minimum level of air leakage?
• Are quality management approaches appropriate instruments to push and/or pull market players? What are the pitfalls to avoid? What can be learnt from pioneering experience in this field, including in the inspection of ventilation systems?
• How does airtightness change with time, and how does that affect the building’s performance over its lifetime?

​The objective of this workshop was to discuss those questions with key experts. It was divided into three parts:

• Philosophy for setting airtightness requirements: recommendations and pros and cons of various approaches
• Durability of seals and bonds: what we know and where we need to go
• Dealing with airtightness in the construction process: lessons learnt and potential for quality management approaches.