EU

Since the 1970s, many authors have discussed the impact of poor airtightness on building energy use, indoor air quality, building damage, or noise transmission (Carrié and Rosenthal, 2008) (Tamura, 1975) (Sherman and Chan, 2006) (Orr and Figley, 1980). Nowadays, because poor airtightness affects significantly the energy performance of buildings, and even more significantly with low-energy targets, many countries include requirements for building airtightness in their national regulations or energy-efficiency programs.

From September 2015 to March 2016, UTC engaged in a major refurbishment of its Design and Research Center located in Culoz (France).

In-situ performance of mechanical humidity-based mechanical exhaust ventilation (RH-MEV) is characterized in this study. This ventilation system includes fully-mechanical air inlets in the dry rooms and exhaust units in the wet rooms: the extensions and retractions of a hygroscopic fabric modify their cross-sections upon hygrometric changes in their environment without the need for motors or electronic sensors. 

With 35 years of existence and more than 10 million equipped dwellings, mechanical humidity-based demand-controlled ventilation (RH-DCV) can provide a comprehensive feedback on installation, aging, and maintenance of its components. Their working principle is based on the extensions and retractions of a hygroscopic fabric, which pulls on a shutter to modify the device’s cross-section – hence the airflow – upon humidity changes in their environment. 

The communication presents the Technical Appraisal Procedure followed in France for Demand-Controlled ventilation systems through the illustration of the use of a thermo-hygro-aeraulic nodal model called MATHIS developed by CSTB. The calculations methodology is described. Its application is illustrated for different family of ventilation systems currently under the scope of the procedure. The needs and the current developments for a better modelling of Indoor Air quality are lastly exposed. 

Demand controlled ventilation systems are representing a large majority of installations in France. They are commonly used for more than 35 years. The strong development of these systems can be explained by the French regulatory framework for air renewal. These demand controlled systems have been developed in order to optimise the energy consumption and at the same time to ensure indoor air quality and building durability. In residential buildings, demand control is based mainly on humidity whereas in commercial buildings it is based on occupancy and/or CO2 levels.

Recent studies have shown that ventilative cooling reduces overheating, improves summer comfort and decreases cooling loads. Therefore, it is considered as one of the most efficient way to improve summer comfort. Although, HVAC designers still lack of guidelines to improve the energy and comfort efficiency of their installations.  

The test lecture rooms of KU Leuven Ghent Technology Campus are one the demonstration cases of IEA EBC Annex 62: Ventilative Cooling. This nZEB school building is realised on top of an existing university building and contains 2 large lecture rooms for maximum 80 students with a floor area of 140m² each. An all air system with balanced mechanical ventilation is installed for ventilation, heating and cooling.

Ventilative cooling (VC) is an application (distribution in time and space) of air flow rates to reduce cooling loads in spaces using outside air driven by natural, mechanical or hybrid ventilation strategies. VC reduces overheating in both existing and new buildings - being both a sustainable and energy efficient solution to improve indoor thermal comfort. VC is promising low energy cooling technology that has potential to substantially reduce the use of mechanical cooling in airtight and highly insulated buildings.

Even in Northern European climates, overheating in many Nearly Zero Energy Buildings is a barrier to year round occupant satisfaction with the indoor thermal environment. Improved energy performance and enhanced thermal comfort should not be perceived as a rigid dichotomy of concepts. However, an acceptable thermal environment, during extended cooling periods now present in NZEB’s, can come at a high energy cost if mechanical cooling is used.