ventilation

In order to reduce the primary energy consumption of buildings, highly efficient heat recovery of the HVAC system is indispensable. A reduction of the fresh air rate is not advisable; Indoor Air Quality (IAQ) is essential for the health and wellbeing of the user. In order to nullify the additional pressure loss of the heat recovery unit a mechanical ventilation system is needed.

Cooling in high ambient temperature (HAT) countries is a major energy consumer. In Kuwait, 70% of the electricity generated is consumed on cooling residential and commercial buildings. Because of the extreme temperatures in the summer, which can reach 50℃, outdoor fresh air vents are closed because AC units are incapable of cooling air at such elevated temperatures. Consequently, this has significantly reduced indoor air quality (IAQ) in residential and commercial buildings for indoor occupants.

In future building regulations, building performance is going to be extended to global performance, including indoor air quality (IAQ). In the energy performance (EP) field, successive regulations pushed for a "performance-based" approach, based on an energy consumption requirement at the design stage. Nevertheless, ventilation regulations throughout the world are still mostly based on prescriptive approaches, setting airflows requirements.

In the UK, people spend over 90% of a day indoors. On weekdays, when outdoor air pollution concentrations peak in the morning and in the late afternoon, people are usually either in non-domestic premises or on their way to/from non-domestic premises. Therefore, establishing the distributions of indoor air pollutant concentrations in non-domestic environments is essential to model human exposure to hazardous air pollution, especially for vulnerable populations, such as schoolchildren or patients in hospitals.

Under the influence of biological hazards including COVID-19, it is required sufficient ventilation to decrease the infection risk in the indoor area. In particular, the natural ventilation with window opening is recommended in rooms with inadequate ventilation. However, the ventilation rate, energy loss, and indoor thermal environment with window opening in air-conditioned room varies hourly with given environment. In addition, opening windows in winter causes serious problems such as deterioration of the indoor thermal environment and reduction of absolute humidity.

Deep Energy renovation (DER) adopts a whole building approach and achieves much larger energy savings than shallow energy renovations that typically only included a small number (one or two) of upgrade measures. DER includes the installation of high levels of insulation, uses renewable energy technologies and minimises uncontrolled air leakage by achieving air permeability levels no greater than 5 m3/h.m2 to achieve building energy ratings (BER) of at least A3.

This paper reports preliminary analysis from a large field study of 100 university classrooms in Central Texas. Lecture classrooms and auditoriums were sampled for three consecutive weekdays in the 2019 – 2020 academic year. Carbon dioxide (CO2) concentrations, used as a marker for both ventilation and exposure, and temperature were measured in the general room area and when able, the supply airstream. HVAC control data that relates to ventilation was also saved for comparison.

Ventilation and source control (e.g. using low volatile organic compound (VOC) emitting materials) are two recommended approaches to control indoor air pollution and VOC’s in particular. Decisions on how to minimize exposure can be supported by indoor air chemistry modeling, since the relationships between VOC’s, their precursors, and building ventilation is so complex. For example, modeling could be used to examine the impact of altering building ventilation.

Many differences exist between countries in the requirements and regulations for ventilation of dwellings, offices, classrooms and other spaces. Sometimes the variation of the ventilation requirements for the same building type between countries is more than a factor of five. There are strong drivers, e.g., climate change, to reduce energy consumption for HVAC and therefore these variations are worth examining. Before reducing ventilation rates, it is critical to understand the reasons behind them.