English

There is a trend to perform more ventilation and air infiltration measurements in buildings, either to strengthen commissioning procedures or to learn from field data. This trend is stronger in nearly zero-energy buildings projects or programmes given the significant share of ventilation and infiltration losses on total building energy use.

An increasing number of countries (e.g. Czech Republic, Denmark, France, Germany, Ireland, Netherlands, Norway, Portugal, UK) include in their regulations either required or recommended minimum airtightness levels with or without mandatory testing. The number of tests performed on a voluntary basis is rapidly increasing either because of the energy penalty for untested buildings in the calculation method or due to the specific requirements of a given program. Furthermore, mandatory testing came gradually into force in the United Kingdom, Portugal, Denmark and France.

There exist several initiatives in different parts of the world to bring a stronger basis to ventilation requirements in relation to indoor air quality and health issues, for example, at LBNL in the US (Healthy efficient homes program), within the HealthVent project in Europe (2010-2012), at Health and Wellbeing project in Japan, Development of healthy and clean residential building standard in Korea (2008-2012) or within the French Observatory for Indoor Air Quality (running since 2001).

While it is generally accepted that ventilation-whether natural, mechanical or hybrid- is needed to provide acceptable indoor air quality and prevent building damage, there are debates about the actual performance of these systems and how deviations observed affect the overall building performance.

The current development in building energy efficiency towards nearly-zero energy buildings represents a number of new challenges to building design and construction. One of the major challenges is the increased need for cooling present in these highly insulated and airtight buildings, which is not only present in the summer period but also in the shoulder seasons and in offices even during occupied hours in winter. In most post-occupancy studies of high performance buildings in European countries elevated temperature levels is the most reported problem, especially in residences.

With the trend towards low-energy buildings, the importance and the interest for building air tightness is increasing. This implies an increasing number of tests, calling for increased attention to the quality of those tests including the way the test results are used to justify for programme or regulatory requirements. In turn, those tests put pressure on builders and craftsmen to reliably attain good airtightness levels. The project will review existing approaches and will analyse their pros and cons.

There is no doubt that, as part of this tendency to move to nearly zero energy buildings, in most climates buildings have to become more airtight. Should there be specific airtightness requirements? If so, what level is to be required? Should there be a minimum level of air leakage? This is the context for this project regarding the ‘philosophy about airtightness requirements’.

There are several national initiatives to collect air leakage data from field measurements buildings as a whole, building components, or ductwork systems. However, at this stage, there is no structured communication between these actions although they could mutually benefit from sharing their experience and encourage other similar initiatives in other countries having in mind the lessons learnt from the previous ones.

The European standard EN 15251 specifies design criteria for dimensioning of building systems. In detail, it proposes that the adaptive comfort model is used, at first, for dimensioning passive means; but, if indoor operative temperature does not meet the chosen long-term adaptive comfort criterion in the “cooling season”, the design would include a mechanical cooling system. In this case, the reference design criteria are provided accordingly the Fanger comfort model.