English

This paper presents different ventilation solutions for the retrofit in existing school building with a special focus on historic buildings. These building usually pose a major challenge for the integration of energy efficient ventilation systems, i.e. with heat recovery. For decentralized systems, the ductwork can be minimized by wall integrated heat recovery units, whereas for central systems, a horizontal air distribution in the attic combined with vertical ducts was found to be a possible solution for listed buildings.

In 2011, the Danish Energy Agency initiated a study into ventilation solutions for the retrofit of schools to identify the most promising technologies. The reason was an increasing awareness that the ability of school children to absorb, adapt and use knowledge was affected negatively by inadequate ventilation rates. This paper presents an output of this study. A method for evaluation of the ventilation systems is proposed. The method consists of three categories with a clear separation to create a scoring board that facilitates transparent and unbiased evaluation.

Studies show that environmental conditions in schools are often inadequate, even in developed countries, and that they are frequently much worse than in office buildings. Outdoor air supply rates in schools are considerably lower than in offices, in many cases even lower than those observed in dwellings.

In an extensive simulation study using a multi-zone airflow and contaminant transport calculation software (CONTAM) recommendations for the supply air rates for residential housing were derived as input for the revision of the Austrian standard ÖNORM H 6038 (2014). The floor plan, the occupancy and the contaminant and humidity sources are modelled to represent a typical Austrian housing situation. A humidity buffering model is also implemented. Based on common thresholds for CO2, relative humidity (r.h.) and TVOC the so-called relative threshold deviation is determined.

Mechanical ventilation performance is a key issue related both to energy efficiency and indoor air quality. There are several techniques for measuring ventilation rates in buildings, such as blower boor tests, flow hoods, VAV box measurements and tracer-gas techniques. From several decades ago, tracer-gas techniques are recognized as the most widely employed method to estimate air exchange rate in buildings. These methods are based on the study of the temporal evolution of the concentration of an injected gas.

Airborne particles released from surgical team members are major sources of surgical site infections (SSIs). To reduce SSI risk, ultraclean-zoned ventilation (UZV) systems have been widely applied, supplementary to the main operating theatre (OT) ventilation. Usually, OT ventilation performance is determined without considering the influence of staff-member posture and movements. Whether the surgeon’s posture during surgery influences particle distribution within the surgical area is not well analysed and documented.

Air curtain assisted range hoods are very customary in large industrial kitchens. They allow to increase the capture efficiency of the range hood while lowering the net exhaust flow rate. For applications in residential settings, there is a lack of data on the performance of air curtain assisted range hoods, as well as a lack of information on the required settings and boundary conditions to come to the successful application of air curtain assisted range hoods.

Carbon dioxide (CO2) has traditionally been assumed innocuous at the typical levels indoors, and merely an indicator of metabolic emissions from humans (bioeffluents). Recent studies suggest that exposure to pure CO2 at concentrations of 2,500 to 4,000 ppm, the levels that occur periodically indoors, can have negative effects on mental performance in form of reduced ability for making decisions, typing and proofreading. Present study aimed to examine further these effects. Twenty-five human subjects were exposed to elevated CO2 with and without bioeffluents in a chamber.

The field research project MONICAIR indicates that ventilation systems that fully comply with Dutch building codes show large differences in their IAQ-performance in habitable rooms during heating season and do not always achieve acceptable IAQ-levels [lit.1]. The results indicate that there are considerable differences in the actually achieved air-exchange rates per person during presence in habitable rooms. System averages on CO2-excess doses per heating season (an indicator for the duration and the amount of the excess above 1200 ppm CO2) vary from 68 to 349 kppmh per person.

Ventilation’s historical goal has been to ensure sufficient air change rates in buildings from a hygienic point of view. Regarding its potential impact on energy consumption, ventilation is being reconsidered today. An important challenge for low energy buildings lies in the need to master airflows through the building envelope. Data collected from controls in 1287 recent dwellings shows us that 68 % of the dwellings don't respect the French airing regulation.