Durability of building airtightness, review and analysis of existing studies

Mandatory building airtightness testing has come gradually into force in European countries mostly because of the increasing weight of building leakage energy impact on the overall energy performance of low-energy buildings. Therefore, airtightness level of new buildings has significantly improved in the last decade.
However, until now, low expertise is available about the durability of building airtightness at mid- and long-term scales.
The Durabilit'air French research project aims at improving our knowledge on ageing of airtightness products onsite and in laboratory controlled conditions.
This paper is issued from the first task of the Durabilit'air project: the "state of the art". It presents a comprehensive review of studies that deal with building airtightness durability, using mostly as references the AIVC publications but also specific studies from UK, Germany, Sweden and France. It covers field measurements, accelerated ageing in laboratory, seasonal variations and also exposure loads of the air-barrier.
Regarding field measurement studies, it seems that the envelope airtightness decreases during the first years after achievement and then stabilises. The main result of this review is a list of key elements that may govern airtightness variations:
• Measurement uncertainty and how it could be reduced
• Structure movements
• Shrinks of mastics in the first weeks when the house gets heated for the first time
• Drilling of the air-barrier due to the installation of new equipment
• Ageing of assembly due to unsuitable association of products and bad implementation conditions
• And, of course, normal ageing of products.
Such information will be useful for future field measurement campaigns. Besides it is necessary to perform leakage detection together with measurements to be able to explain changes in airtightness level.
The analysis of laboratory ageing studies showed that there is actually no standardised protocol to characterise durability of product assemblies. However, due to the various natures of airtightness products, it seems difficult to define an accelerated ageing universal protocol that would be equivalent to a known amount of years of natural ageing. This paper gives pro and cons of various alternatives to assess the durability of airtightness products in laboratory.