Evaluating Ventilation Regimes
Tas - A Comprehensive and Flexible Modelling Tool for Evaluating a Wide Range of Design Scenarios
Cross ventilation and single sided ventilation
Using recorded hourly weather data containing solar radiation, air temperature and wind
speed and direction, an energy and air flow balance is calculated at hourly time steps.
Simple cross ventilation is evaluated on wind speed and direction, modified by the relative
height of openings and surrounding buildings. Single sided ventilation is based on the internal
to external temperature difference and the physical height of the openings.
Combined wind and stack driven ventilation
Both wind and stack pressure driven air movement can be calculated simultaneously. The rate
of air flow is determined for each opening in conjunction with flow between internal spaces.
The balance of energy and air flow is performed for all spaces at each hourly time step,
allowing the effects of internal gains to accumulate as the air travels through the building.
An office area on the leeward side of a building may, therefore, receive air which has been
raised in temperature by its passage through other office areas and an atrium space.
Single sided ventilation via a double facade
Where external noise presents a problem, natural ventilation may be achieved using a double
facade. Wind and stack pressure drive the air flow up through the void created by the double
facade. The flow rate is determined by a number of factors including wind speed and the height
of the top of the facade void, or, in still conditions, the temperature generated inside the
void. Single sided ventilation occurs between the occupied spaces and the facade void. The
higher floors will receive air from the void which has, at least in part, already been through
other spaces with the consequent rise in temperature.
Multiple regime ventilation in the same building
Any combination of ventilation regimes can be included in the same building model. Control of
open area for windows etc can be placed under the influence of a range of internal variables
and in addition linked to climate parameters. Aperture opening can be controlled individually
or in groups from the performance of any space or group of spaces. Solar control devices may
also be operated with the same level of flexibility in combination with the modulation of