Many existing offices either overheat in the summer or use excessive amounts of energy to maintain acceptable temperatures. The reasons are increasing internal heat gains from office IT equipment, poor efficiency lighting systems, density of staff and original poor building design causing excessive solar gains. The trend is for problem offices to have AC systems replaced - at the end of the life of the existing services - or installed in previously naturally ventilated offices when refurbishment occurs.
In connection with the research programme "Healthy Buildings", a building with indoor air quality problems was selected for further investigations. A Danish town hall was chosen because of many complaints over several years. A full-scale mock-up of a typical town hall office was built in the climate laboratory. A new heating and ventilating system and a new control strategy were chosen and implemented into the town hall.
Indoor and outdoor particle concentrations and ventilation rates were measured versus time ina large office building without tobacco smoking. Periodically, high efficiency filters replacedthe normal filters in air handling systems. For all particle sizes, indoor concentrations variedconsiderably with time. Even with the normal air filters, which have a low efficiency forsubmicron particles, number concentrations of submicron particles were a factor of three tosix smaller indoors compared to outdoors.
The paper presents results from the numerical modelling of the flow field in an existing ventilated office room. The numerical procedure is based on the 3D Reynolds equations closed by the k-e turbulence model and an equation for temperature solved by the finite volume method. The boundary conditions are set in accordance to detailed measurements of the velocity distribution in the air supply diffuser. The established complex flow conditions in the room, which are due to the presence of furniture and buoyancy forces, are presented.
In order to evaluate the impact on indoor air quality of different installation and ventilation strategies, the modelling of indoor air pollutant transfer has been developed in the CLIM2000 software (thermal and airflow code). Then, these models have been used to simulate the evolution of indoor air pollution in an office building floor for a week in winter under different ventilation strategies. The selected pollutants are CO2, CO, NO2 and HCHO and the sources are outdoor pollution for all pollutants and occupancy for CO2. So far, humidity has not been taken into account.
A secondary analysis of the Dutch prevalence study by Zweers et al shows that office buildingswithout artificial cooling and with operable windows have a lower risk for health symptoms andcomfort complaints than office buildings with artificial cooling and sealed windows. Temperature ,simulations of various office buildings show that in the Dutch climate zone thermal comfortduring summer conditions is secured without the use of artificial cooling if a number of essentialdesign criteria are met.
During the last decade, an increasing interest in Underfloor Air-Conditioning (UFAC) systems has emerged. This is due mainly to an increased demand from employees for a greater control over their working environment. And the building and its engineering systems not only have to be designed to achieve the high standards of environmental control at economical cost, but also thermal comfort is an important factor that influences occupants' satisfaction with the indoor office environment.
Achieving optimized partial improvements of the indoor climate may often be better than to know all optimal levels. The purpose of this study was to investigate the relative importance of temperature, noise, draft and window area. 30 heat-acclimatized subjects participated in 10 exposures in single person climate chambers. Each exposure lasted three hours. During an exposure, the subject was free to optimize the operative temperature at a link to either draft, noise or window area. For each pair of parameters, three linear links were tested.
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