Thermodynamic analysis of buildings with natural ventilation and indoor air quality

The aim of this study is to analyse the behaviour of natural ventilation techniques in low-rise commercial buildings in terms of Indoor Air Quality (IAQ). Verifying how the outside air flow can enter a building using natural ventilation techniques to check if they are suitable to be bound by the regulations, thus validating passive techniques for ventilating buildings. With the emergence of the regulation of thermal installations in buildings (RITE) in Spain, the basic regulatory framework that regulates the requirements in energy efficiency and security is set up, thermal installations in buildings need to meet the demand of welfare. It is compulsory to vent all conditioned spaces of a building using fans, which involves installing ducts and equipment. With the RITE approval is compulsory to install them in buildings that do not have cooling demand. This implies an increase in the cost of ventilation and operation. An analysis of different foreign regulations related to natural ventilation is performed, the UK regulations Building Bulletin 101 - Ventilation of School Buildings and the ASHRAE Standard 62.1-2007 - Ventilation for acceptable indoor air quality. The design requirements that these regulations prescribe are collected. In these guidelines, it is possible to introduce the necessary outside air in buildings using natural ventilation techniques, in order to maintain IAQ, healthy environments and avoid potential pathologies related to comfort inside buildings. A case study is carried out, designing a low-rise commercial building prototype with natural ventilation systems. It is calculated the size, distances and orientations of the openings necessary in each occupied zone. Subsequently it is checked the design made by computational thermodynamics simulation. The thermodynamic simulation tool used to test the feasibility of natural ventilation techniques is Energy Plus, which by Airflow Network module enables the modelling of natural ventilation in buildings. Additionally, it is also used Computational Fluid Dynamics (CFD) simulations to properly design natural ventilation systems and to validate inside thermal comfort of the proposed building. Finally, it is verified that in normal weather conditions and proper design of natural ventilation systems, indoor air quality meets the requirements of regulations. In conclusion, thanks to the implementation of this technology we can achieve considerable savings in the implementation and operation, along with a decrease in CO2 emissions to the atmosphere.