19-20 March 2018 | Towards higher-performing buildings: The role of airtightness and ventilation

New Zealand homes and apartments have become more and more airtight and have reached a level of airtightness that requires dedicated ventilation. Despite the fact that there is no airtightness requirement in the New Zealand Building Code, new homes regularly reach an airtightness level of 2-3.5 ACH50. This can be a welcome trend as it allows controlled ventilation and therefore control of the energy demand of the building.

On the contribution of steady wind to uncertainties in building pressurisation tests

This paper analyses the contribution of a steady wind to the uncertainties in building pressurisation tests, using the approach developed in another paper (Carrié and Leprince, 2016). The uncertainty due to wind is compared to the uncertainties due to other sources of uncertainty (bias, precision and deviation of flow exponent).
The main results of this study are:

Impact of airtightness on the heat demand of passive houses in central European climate

Excessive air leakage through the building envelope increases the infiltration heat loss and therefore lowers the energy efficiency. Therefore, very good airtightness is required in case of well insulated buildings equipped with a mechanical ventilation system with heat recovery (e.g. n50 < 0.6 h-1 for passive houses). Although the building industry has progressively adopted strategies to comply with such strict limits, it is still important to study how and how much the airtightness influences the energy efficiency of different types of buildings in different climatic conditions.

The effect of refurbishment and trickle vents on airtightness: the case of a 1930s semi-detached house

As UK homes are insulated and draught proofed in an attempt to reduce wintertime heating demand they become more airtight. Any reduction in infiltration could have a detrimental effect on indoor air quality. Controllable background ventilation provided by trickle vents is one method of maintaining indoor air quality.

The effectiveness of mechanical exhaust ventilation in dwellings

Ventilation systems play an important role in providing a good indoor air quality in dwellings. Mechanical exhaust ventilation systems implement natural vents to supply outdoor air to the dwelling. Natural driving forces, i.e. wind and thermal draught, influence the flow rates through these supply vents. Therefore, the flow rates depend on the weather conditions and vary in time. This study considers the influence of the wind and thermal draught on the operation of a mechanical exhaust ventilation system in a reference dwelling.

Component leakage: potential improvement graphs and classification of airpaths

Last years, interest in airtightness increases among all construction fields and airtightness becomes a major issue in the reduction of energy consumption in buildings. Nevertheless, there is a lack of understanding of air displacements through weak spots in buildings (airpaths). Firstly we develop first the concept of Potential Improvement Graph (PIG chart). These graphs represent the “improvement curves” of a given airpath (airflow indicator against airpath parameter). As an airpath can have multiple significant parameters, PIG charts can be n-dimension graphs.

Long-time durability of passive house building airtightness

An airtight building envelope ensures not only the energy-efficiency of a building, but also a damage free construction. Important to achieve optimal airtightness are the planning, implementation and materials. Long-term airtightness requires efforts in all three aspects. Airtightness products are being tested under lab conditions but these results cannot be transferred one-on-one onto buildings.

Assessment of the durability of the airtightness of building elements via laboratory tests

The airtightness just after the end of a building phase is assumed to be relevant criteria for high energy performance. Testing on site the initial performance of the airtightness via the blower door test has become nowadays a common practice but generally implemented before the occupation of the building. But a lot of questions are still remaining targeting the sustainability of the performances.