English

This paper presents a numerical study of hybrid ventilation in densely populated multi-storey urban apartment units. Seven cases are presented with variation of parameters such as outdoor air temperature, apartment floor heat source and built-in fan power : 3 cases with natural ventilation and 4 with hybrid ventilation. An analysis of thermal comfort and pollutant transport is made from the calculation results.

Results of IEA ECBCS annex 35 Hybvent case studies about the control strategy used in buildings with hybrid ventilation are summed up in this paper : it is easy to design a suitable control strategy for hybrid ventilated cellular offices, but it is much more difficult for the landscapes offices mainly due to automatic central control of windows.

The use of a hybrid cooling system using radiant cooling panels with wind-induced cross ventilation is described in this paper. Its performance is compared to the hybrid system using underfloor air-cooling. The radiant cooling panels system appears more energy efficient and brings more thermal comfort than the under-floor air cooling system.

This study was undertaken in IEA ECBCS Annex 35 to model a hybrid-ventilated room and to implement control strategies. An experimental cell was designed and simulations were performed after having adjusted the thermal models to experiments. The hybrid ventilation proved more performant than traditional ventilation systems.

This paper gives the results of a field study in Danish office spaces with displacement ventilation systems. Draught was identified as a serious problem. Half of the 227 occupants were not satisfied with indoor air quality. Occupants counteract draught discomfort in blocking air supply diffusers or asking the maintenance staff to increase the supply air temperature. So a very careful design for displacement ventilation is required in order to perform satisfactorily in practice.

Thermal comfort for 227 occupants in 8 office buildings with displacement ventilation was investigated. The occupants' thermal sensation was close to the predictions by the PMV index. The main conclusion is that draught is the major local discomfort factor for the occupants, mainly at lower leg. The effect of vertical temperature gradients on occupants local discomfort did not appear as evident.

This paper deals with the steady state simulations carried out with the CFD software Flovent along with dynamic building energy simulations using the ESP-r programme applied to three buildings (located in Ireland, Poland and Denmark) intended to be equipped with supply air windows coupled with passive stack ventilation systems. Supply air windows consist of two layers of glazing separated by a ventilated layer. Air enters the cavity at the bottom from outsides and enters the building at the top. Systems design from simulation results is discussed.

Prediction of airflow and pollutant transfers in a simple multizone building may use different approaches such as zonal or nodal modeling methods. This paper proposes to improve the modeling of pollutant transport by coupling nodal and zonal models in the SPARK simulation environment.
Nodal model gives mass airflow rates used as boundary conditions in the zonal model to predict pollutants mass transport. Simulation results are compared with experimental data from the 2 zones testing room Minibat.

Overnight free cooling in buildings brings potential benefits that have been known for some time. This study investigates those benefits when used in conjunction with an under floor air delivery system (UFAD). A detailed study using CFD was undertaken for a building in an airport in the UK with under floor air conditioning system and mechanical ventilation providing fresh air. Results show the energy consumption and peak cooling loads reductions when using night time cooling with outside air during the cooling season.

Advantages of floor supply and floor return systems (UFAD: under floor air distribution systems) are described. They are presented by the author as being capable of better performance (thermal comfort, indoor air quality) than floor supply and ceiling return system. They also offer flexibility and ability to allow individual control.