During the cold seasons, it is possible to use ambient air to cool down the coolants in air-conditioning or other refrigeration applications. Applying this free cooling reduces the energy costs of a refrigeration machine. This paper presents a general method for the economically optimal dimensioning of a free cooling system in which a heat exchanger of the counterflow or crossflow type is applied to the heat transfer between the ambient air and the coolant.

For energy savings, DCV systems are more and more used in ventilation systems but toestimate their energy savings, variation of occupation in the building (in time and number ofperson) must be estimated. We have enquired on real occupation on site in 27 offices and 13meeting room in France. Occupation rates have been monitored either by webcam or byenquiry to the users. Results show very low occupation rates in meeting rooms although mostpeople feel they are very occupied. Yet effective time of meetings and number of occupantsare less than expected.

For energy savings, DCV systems are more and more used in ventilation systems. In France, in nonresidential buildings, these systems are generally controlled by either a CO2 sensor, or an opticalmovement detection (infrared). The part of the study we present here was to determine laboratorytests methods to assess the performances of optical sensors for ventilation application. The pointwas to characterise them by checking their detection in front of some determined movements orevents.

In France, in non residential buildings, these systems are generally controlled by either a CO2 sensor or optical movement detection (infrared).The part of the study we present here was to determine :- laboratory tests methods to assess the performances of CO2 sensors for ventilation application.- the working performances of these sensors, and particularly the long term stability in a meeting room.- a methodology to assess the performances of CO2 DCV system in French technical agreementThe main results of this study are :- it is easy to characterize (to calibrate) the sensors- the long term

Natural night ventilation and an earth-to-air heat exchanger are applied in the low-energy office building ‘SD Worx’ in Kortrijk (Belgium). Temperatures measured during summer 2002 are used to discuss the operation and cooling effect of these passive cool

Ventilation and comfort assessment of buildings is not a new practice in post occupancy evaluation (POE) of buildings. Most evaluations have been based on perceived assessments by the occupants collated through questionnaires asking for a Yes/No response or qualitative scale rating. While this study does not deal with a POE survey, it was initiated by the lack of comfort and overheating complaints of the occupants of the subject university building.

This paper deals with the real behavior of a humidity controlled air inlet, regarding to relative humidity and temperature. It has been often heard, that relative humidity is not the best indicator for detecting a need of ventilation in main rooms (living room and bedrooms) because it is season dependant (the absolute humidity outside varies in a wide range from winter to summer, which should lead the air inlet to be closed in winter and open in summer).

The use of natural ventilation systems continues to be a popular feature in low energy, sustainable building design. One feature of natural ventilation is that, depending upon the prevailing climatic or thermal conditions, the airflow through a ventilator can be bi-directional. Aerodynamically, the ventilator, depending upon its construction, may not perform in the same way for the two different flow directions.

In the 1990's, concern about global warming has resulted in a resurgence of interest in naturally ventilated offices. The Belgian climate is particularly well adapted to apply cooling by natural ventilation. Indeed, except for a few hours a year, outdoor air temperature is lower than indoors. Lots of office buildings have no atrium or chimney to benefit from any stack ventilation. But natural ventilation can nevertheless be organized with only frontage windows either by single-sided ventilation or by cross ventilation.

In the survey study ‘Kantoor 2000’ the HVAC-system of several large office buildings in Flanders was monitored. Some of these buildings use air humidity control, most of them not. This triggered the question : why? In this paper the humidity control strat