Can increased outdoor CO2 concentrations impact on the ventilation and energy in buildings? A case study in Shanghai, China

Abstract

This study presents that increases in atmospheric CO2 levels impact the ventilation and energy in buildings. The most significant impact of ventilation occurs during use, because of the indoor air quality. According to the 2014 IPCC report, observed atmospheric CO2 levels increased at a rate of 1.9–2.1 ppm per year. This study measured CO2 levels in a building in an urban area in Shanghai, China, and analyzed existing ventilation performance and energy simulation in relation to the impact of increased atmospheric CO2 concentrations. As long as the atmospheric CO2 level increased, the outdoor airflow rate had to increase also to maintain an acceptable indoor CO2 level. The ventilation rate was also considered in relation to the surrounding environment. In Shanghai, the average value of CO2 concentrations on an auto road was 550 ± 20 ppm and the average value on a pedestrian road was 435 ± 15 ppm. A building that was surrounded by high traffic roads needed 20–30% more outdoor airflow rate than a building surrounded by pedestrian roads. Accordingly, energy loads in buildings, for heating and cooling were also affected. In order to dilute indoor CO2 level, the thermal ventilation energy and the ventilation energy uniformly provided a 20% energy load increase during the 12 months, while each monthly energy load varied, depending on the season and/or month. By analyzing indoor CO2 levels and the rise in atmospheric CO2 levels, this study determined how these rises impacted the energy consumption of the building, and how to design a new outdoor airflow supply rate to adapt to a changed environmental condition.