Hybrid ventilation of office buildings

The report summarises the Finnish hybrid ventilation development performed in the international project IEA Annex 35, Hybrid Ventilation in New and Retrofitted Office Buildings. An overview of hybrid ventilation in office and school buildings in Nordic countries is given in the first part of the report. An interview survey carried out among Finnish designers and decision-makers shows that an increase of using natural forces in ventilation is expected. Three ventilation concepts for office buildings have been created to provide an alternative for the mechanical ventilation system with air-to-air heat recovery. The concepts are based on a low-pressure mechanical system and demand control of ventilation airflows. These concepts are relatively conservative because the role of the natural driving forces is small and the mechanical cooling is mostly used. This is a conscious choice, which is based on the Finnish climate and the strict requirements for indoor climate and energy use. The simulation results for the office and for the school building indicate that the ventilation rate can be controlled and energy costs reduced with the hybrid ventilation concepts. The life cycle cost comparison shows that lower pressure losses should be taken into use in the mechanical ventilation design practise. Copyright © VTT 2002.