mixed mode

The scientific literature often reports example of educational buildings with extremely poor ventilation performance. An in-field investigation for the environmental and energy assessment of a kindergarten in Milano, confirmed that operable windows were not operated when the average daily temperature dropped below 14 °C, jeopardizing indoor air quality and kids learning performance.

Mixed mode (MM) buildings open up a new arena for energy efficient design. Zoned MM buildings are the most common, particularly in the developing world where only some areas in a building are air- conditioned (AC) based on programmatic requirements while the rest of it is naturally ventilated (NV). Occupants in the NV zone frequently visit the AC zone and are well aware of the conditions there.

In achieving low-energy operation, occupant-controlled mixed mode buildings rely as much on the judicious use of active climate control by occupants as they do on the efficiency of the building services. The extent to which occupants choose to use natural ventilation for creating a thermally comfortable environment is informed in part by the human heat balance, and by the availability and effectiveness of adaptive comfort devices, but is also a function of social, cultural, and local context. Qualitative study is suited to exploring these factors in more detail.

The built environment in China is required to achieve a 50% reduction in carbon emissions by 2020 against the 1980 design standard. A particular challenge is how to maintain acceptable comfort conditions through the hot humid summers and cold desiccating winters of its continental climate regions. Fully air-conditioned sealed envelopes, often fully glazed, are becoming increasingly common in these regions.

In recent years there has been a gradual re-emergence of the use of passive or 'low energy' ventilation and cooling techniques including mixed mode application. It is apparent that many clients developers and agents are reluctant to make a commitment to such 'low energy' buildings due to concerns, albeit unsubstantiated by hard evidence, that such buildings will provide acceptable comfort levels for occupants.