Climate change is now widely recognized as the major global environment problem. Greenhouse gas emission is treated as the key issue causing the climate change. Heating, ventilation and air conditioning system (HVAC) energy consumption typically accounts for around 40% of total energy use in buildings and around one-fifth of the national energy use. Thus, minimizing the energy consumption by air-conditioning systems would help to reduce greenhouse gas emission. Elevating indoor temperature to minimize the energy consumption therefore was recommended by several governments in East Asia. Stratum ventilation system was proposed to accommodate such trend of elevated room temperature. It has been proved that stratum ventilation performs well in maintaining thermal comfort, providing good air quality and saving year-round consumption energy. However, there are still some factors influencing ventilation performance, which include air terminal types, air terminal layout, number of air terminal and supply airflow rate. Up to now, the knowledge on the effects of these factors on stratum ventilation is extremely limited. In order to have an in-depth understanding of stratum ventilation and provide reliable and scientific design guidelines for its application, in this dissertation, effects of air terminals on stratum ventilation are investigated. Both experimental and numerical methods are applied. The performance of stratum ventilation is evaluated by the following criteria: airflow pattern, temperature distribution, thermal sensation and comfort feedback, air diffusion performance index, the percentage of people dissatisfied due to draft, local mean age of air and carbon dioxide concentration. Effect of four types of air terminal including circular diffuser, square diffuser, perforated diffuser and double deflection grille on stratum ventilation performance was investigated. The results indicate that air terminal type has significant effect on airflow pattern. Under the same experimental conditions, circular diffuser performs better than the other three types. With circular diffusers, more uniform thermal comfort environment and better indoor air quality can be achieved. Comparing with other three cases, the average thermal sensation for double deflection grille case is relatively cool. Occupants sitting in the air jet regions may experience draft in this case. The fabric diffuser made of polymer was found to create a clean, healthy and comfort indoor environment. In this dissertation, its technical feasibility for stratum ventilation is studied. Its performance is compared with that of double deflection grille. The results show that at the same airflow rate, fabric diffuser has a higher face velocity because of smaller effective area, but it could provide relatively uniform velocity and temperature distributions and acceptable air diffusion performance. Fabric diffuser thus can be a better choice for stratum ventilation compared with double deflection grille, and it also helps to improve the appearance of stratum ventilation. Totally four variation of air terminal layouts are studied to determine the optimal design of stratum ventilation. Exhausts were located at (a) middle level of the wall opposite to the supplies; (b) low level of the same wall as the supplies; (c) low level of the wall opposite to the supplies and (d) the ceiling level, respectively. From the experimental and simulated results, similar performances with the exhausts located at middle or low level of the wall opposite to the supplies are observed. In case with exhausts located at the ceiling, temperature and effective draft temperature in the occupied zone is relatively low. However, with this arrangement more fresh air could be supplied to the breathing zone. For the same indoor design temperature, with this arrangement the supply temperature could increase at least one degree, which helps to save energy. Better performance is found for the case with the exhausts located at the low level of the same wall as the supplies. Thermal comfort and good air quality can be achieved for the indoor environment. This arrangement also helps to save space needed for system installation. For air distribution design, supply air velocity is an important parameter, which can be affected by the number and size of air supply and supply airflow rate. In order to obtain a good air distribution performance, the balance between the supply airflow rate and the number of supplies is investigated. At the airflow rate of 7, 10 and 15 air change per hour (ACH), air distribution performances with 4 and 7 supplies are studied respectively. It is found that at the same airflow rate, increase number of supplies improves air distribution performance to certain extent. Cases with 4 supplies at 10 ACH and 7 supplies at 15 ACH perform better. In these cases, the face velocities of supplies are around 2.0 m/s. Thus, it is suggested for stratum ventilation design. Finally, based on the database, the importance of different factors that can affect the air distribution performance of stratum ventilation is evaluated. It is found that air terminal type and supply airflow rate have significant influences on thermal comfort of air jet regions, whereas air terminal layout has a moderate influence. Keywords: Stratum ventilation; Thermal comfort; Indoor air quality; Experimental study; Numerical simulation; Air terminal type; Air terminal layout; Airflow rate; Air diffusion performance index (ADPI); Percentage of dissatisfied people (PD); Mean age of air; Concentration of Carbon Dioxide (CO2); Fabric diffuser.