Utvärdering av VAV i nybyggt kontorshus

Sammanfattning: VAV (Variable Air Volume) system has been studied in a newly constructed office-building. The goal for the study has been to evaluate how the ventilations system work in practice, if adjustments can be made to achieve an more energy efficient system and to evaluate if other alternative ventilation systems is to be preferred in the further. The degree project has been executed at Helenius Engineering Firm who is working with the environment, media systems, HVAC and energy in buildings. The building that has been studied is owned and operated by Akademiska hus. Literature studies, visits at site, inventory, review of system documentation, energy analyses, interviews, key figures, LCC, sand energy- and indoor climate simulations has been made to study the building. Where appropriate some tools from Six Sigma have also been used. How to achieve an energy efficient system and a pleasant indoor climate is studied with human health and well-being as base for the indoor climate requirements. Technical support systems such as ventilation systems have to be designed so that an acceptable indoor climate can be achieved. The building itself along with the type of activity create prerequisites and limitations in regards to how energy efficient the system can be. In the two first visits which were conducted in the start of the project it appeared that the ventilation system were not functioning as expected. In a later visit, some of the issues were solved and in a recent meeting between Akademiska hus and the tenants, the tenants seemed pleased with the indoor climate. Analyses of service requests statistics, interviews together with cause and effect analyses has revealed that there has been issues with the indoor air quality ant that the rooms has been perceived as to warm or too cold. Some of the causes has been loose sensor cables, reduction of the temperature in the room during absence from people during winter time and short circuit between intake of outdoor air and the outlet of exhaust air on the roof. The building has a low energy consumption compared to key figures presented by Repab. Energy and indoor climate for alternative temperature settings has been simulated in the program IDA and shows that the energy consumption can be reduced. The interviews give a picture that VAV systems are preferred when they are well functioning. But VAV systems have disadvantages such as they are complex and require good knowledge and understanding about the control system from all people concerned. Many components and functions give more opportunities for failures. In comparison with other ventilations systems, VAV according to cost estimates and LCC are the most cost effective ventilations system for offices.