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One of the major sources of problems in dwellings -if not the main source- is moisture, especially due to surface and interstitial condensation on walls and roofs. For this reason, it seems important to evaluate the current standardisation and reference documents dealing with moisture and eventually to develop new assessment methods. This is the goal of the Belgian project "Moisture problems in roofs", carried out by BBRI, KUL, RUG and W&K. The first step is to collect a large number of indoor climate measurements in recently built dwellings built.

The Sint-Pieterschurch in the city of Ghent is one of the largest churches of the city. It was built in the 17th century. The city council wants to use the church not only for its religious functions, but also for cultural activities as concerts and exhibitions. To be able to do this the thermal comfort of the visitors has to be guaranteed. At this moment the church has no central heating system. Gas heaters are used during services. Installing a central heating system will influence the humidity and moisture behaviour of the church.

Approximatly over 90 percent of buildings in Poland are ventilated in a natural manner. Thescale of problems in the functioning of ventilation in our opinion is serious.In about 3 million apartments inhabitants use gas water heaters, burning fuel in an openchamber. Therefore in these types of apartments the use of mechanical exhaust ventilation isforbidden.Experiences in using mechanical ventilation is not always positive (frequent complaints aboutthe excessive noise of the installation and the high consumption of energy by the fans).

Research has shown that highly efficient solar powered ceiling fans improve thermal comfort and potentially provide health benefits when air conditioning or conventional ceiling fans are not available, such as during the 2003 summer heat waves in Europe, and in many undeveloped areas of the world. Ceiling fans can improve the spatial effectiveness of heating, ventilation and air conditioning (HVAC) systems. They can reduce air conditioning energy use if occupants increase thermostat set-points and reduce frequency of operation, and if waste heat from the fan motor is minimized.

Local control of ventilation in large buildings is considered to be a main issue in energy savings regarding the huge energy losses that are usually induced by such large volumes. An efficient ventilation system and the development of local control ventilation strategies could prevent large buildings from having an unsuited or overvalued ventilation and reduce significantly the energy consumption.

In this paper, the current situation of Portuguese residential buildings in terms of ventilation systems ispresented. The indoor air renewal is, normally, obtained by providing fresh air exclusively by air leakage of doors and windows and their occasional opening and exhausting the air through ducts placed in kitchens and bathrooms. A recent revision of the Portuguese standard NP 1037-1, concerning natural ventilation of dwellings, is studied and its influence upon heating energy consumption and indoor temperatures is reported.

More than 700 million of measured data, 730 days, 55 dwellings: the HR-VENT hybrid ventilationdemonstration project applied in NANGIS (France) on a set of occupied collective dwellings is closely linked to its stakes. From January 2004 up to December 2005, the values of humidity, temperature, pressure, opening surface and gas appliance operation are saved every minute in all the wet rooms by specifically developed sensors.

To get closer from comfort and energy levels of new buildings conciliating economical viability for the big retrofitting market : the challenge opens the way to the most innovative ventilation systems. In this context was born a new hybrid ventilation system mixing demand-controlled components and low pressure assistance fan. HR-VENT is an exceptional large-scale monitoring launched in France in the suburb of Paris in order to measure the effectiveness of this new system, as well as to improve the knowledge on the hybrid and standard natural ventilation.

The purpose of this study was to assess indoor air quality as well as actual ventilation in renovated school classrooms. A typical naturally ventilated school building was chosen to install different air inlet units in identical classrooms. Later measurements of carbon dioxide concentrations, temperature, relative humidity and air velocity were carried out. Actual measured values were compared with Lithuanian and European standards. This study gives the evaluation of renovating process in the Lithuanian schools, which began in 1997.

How can hybrid ventilation and natural ventilation significantly improve the indoor climate in retrofitted office and education buildings? During the last 5 years hybrid ventilation and natural ventilation have increasingly been utilised in refurbished and retrofitted buildings with great results. Utilising a newly developed system solution concept, it is illustrated how intelligent control of buildings can establish a good indoor climate with satisfied users. This article contains results from 4 building cases including two schools and two office buildings in Denmark and Switzerland.