ventilation

Available time for building construction is getting shorter, therefore the number of buildings which are built with lightweight building elements (LBE) is increasing. LBEs are elements of greater dimensions with low specific weight and low thermal transmittance. Their characteristic is also low thermal stability. By upgrading LBE with dual ventilated cavities (DVC) with counter flow becomes standard LBE a thermally activated building construction with increased thermal resistance and thermal stability. It enables using of solar radiation and heat recuperation from used air.

In cold and moderate climates, improvements in building shell insulation and air-tightness imply a shiftin heating loads from transmission and infiltration towards ventilation. Heat recovery from the ventilation airflow plays an increasingly important role in minimising energy needs. Such heat recovery systems rely on the input of electric power (to drive fans, heat pumps, etc.) in order to recover thermal energy. Since electricity input is relatively small compared to the amounts of thermal energy recovered, such systems are efficient from an energy viewpoint.

The absolute necessity of air renewal to maintain indoor air quality and thermal comfort in buildingsfaces the major issue of energy consumption reduction and optimisation in building sector. Manystudies carried out so far point out the performances improved thanks to the recourse to ventilationstrategies and control algorithms in the aim of optimising the energy consumption of air renewal, butvery few of them could assess the performances in the particular case of large buildings despite thepotential energy gains it represents considering the great volume and huge air flow rates induced.

This presentation will make the audience aware of the importance of ISO-recognized certificationprograms in the testing adjusting and balancing and commissioning of HVAC systems. ImportantISO 17024 standards will be covered as well as their importance. Many faults have been found inexisting testing adjusting and balancing and commissioning certification programs ranging fromconflicting issues within the organization and their testing procedures; political control over theprocess; inconstant certification methods; geographical differences.

In this study the COwZ model (COMIS with sub-zones) was modified to allow dynamic simulations ofindoor thermal conditions, humidity and pollutant transport and concentrations throughout wholebuildings. The new version of COwZ may be used to predict the impact of heat supply and ventilation options on indoor conditions, particularly temperature and humidity, over extended periods, with dynamic weather conditions and varying occupant activities.

The actions to limit the energy consumption and the electricity demand lead in Europe and inFrance to think about the energy labelling of the consumption of the fans used in ventilationsystems. This is a complicated task as it has to take into account the multiple possibleoperating conditions, the eventual presence of a regulation system and the type of use.A study supported by Ademe has been carried out in order to propose a method for labelling ofthe ventilation units. This study was divided in four phases.

The average air tightness of the ventilation ductwork in France is rather poor, corresponding toa 3A class. This is mainly due to air leakage in the fittings. Because of difficulties encounteredduring the implementation as lack of space, access problems or short time to proceed theinstallation, these fittings are not sealed enough, with mastic or adhesive tape.In order to limit this risk of leakage and to limit sealing operations on site, manufacturerspropose components equipped with joints. Some years ago, CETIAT has tested in itslaboratories different kind of such components.

Indoor aerosol particles, their concentration and deposition in displacement, their movements in two ventilated rooms are compared numerically. For the simulation of particle tracks, the discrete trajectory model is adopted whereas the Eularian method is used for solving the continuous fluid flow.

For that study an experiment was conducted during 2 months, in a call center : each week 26 operators returned questionnaires recording their environmental perceptions and sick building syndrome symptoms. In parallel, the recording of their average talk-time was monitored every 30 minutes.The results of that study confirm that increasing outdoor air supply rates and replacing used filters with new ones has a positive effect on health, comfort and productivity of workers.

This paper gives the main results of a thesis whose main objective was the comparison of numerical and experimental values of indoor air quality. The tests were carried out at the CSTB . That thesis has permitted to propose an index for the appreciation of the efficiency of the elimination of pollutants.