Description

In this case the single zone office building will be cooled using natural displacement-ventilation and a chilled floor. Ventilation openings are located in the North (high level outflow) and south façade (low level inflow). The windows are open during working hours.

Cooling Strategy

Outside air cooled by contact with the chilled floor is used to remove heat from the building in a displacement-ventilation configuration.

EnergyPlus Models Used

Displacement-Ventilation model (UCSD Displacement Ventilation)
COMIS (buoyancy driven airflow)

Simulation Results

Analysis

Although chilled floors are known for their limited heat removal ability, the results obtained are very good with a clear reduction in overheating hours. The internal conditions can be considered adequate in all cities for the lower of the two gains scenarios.

Whenever the average internal temperature is lower than the outside temperature, natural upwards driven stack ventilation cannot be maintained, the airflow direction reverses and the internal flow mixes (the stratification is destroyed). This problem occurs in a significant percentage of the time in the present case. There are two consequences of this behavior: increased internal temperature (as the internal gains are no longer driven into the upper unoccupied layer) and decreased air quality (a characteristic of the mixed ventilation that exists in these conditions).

There are two ways of dealing with this problem: add mechanical extraction fans to ensure the correct airflow direction or increase the "stack power" of the building. This second option is pursued in the next section by using a solar chimney.