Reading: The Green Studio Handbook by Alison G Kwok et al (Part 1)

Cross Ventilation

Cross ventilation cooling is only viable when the outdoor air is at least 3 degrees Celsius cooler than the indoor air.

Outdoor airflow rate is another key capacity determinant – the greater the airflow, the greater the cooling capacity.

Siting should avoid external obstructions to wind flow (such as trees, bushes, or other buildings).

On the other hand, proper placement of vegetation, berms or wing walls can channel and enhance airflow at windward (inlet) openings.

Cross ventilation for night-time structural cooling (when adequate wind speed exists) should be directed to maximise contact with thermally massive surfaces.

High outdoor relative humidity may compromise occupant comfort.

Clearstories do not assist in occupant level air movement. Cross ventilation through lower inlets provide occupant level air movement.

Orientation of the building to the prevailing winds will maximise airflow.

Substantial heat sources should be placed near outlets, not near inlets (which is determined by the direction of the wind).

Stack Ventilation

Stack Ventilation is a passive cooling strategy that takes advantage of temperature stratification it relies on two basic principles:

1. As air warms, it becomes less dense and rises.

2. Ambient (hopefully cooler) air replaces the air that has risen.

Stack ventilation will only work for thermal comfort conditioning when the outside air temperature is cooler than the desired inside temperature.

In the BRE Building in the UK, ventilation stacks are located along the southern face of the building.

These stacks are glazed with a translucent material so that solar radiation heats the air in the stack, causing an increase in airflow within the building.

Stacks need to be double the height of the building if they ar to serve all floors of a building, or that they only serve a portion of the total floor area.

Exterior finishes and landscaping (plants, misting, and ground covers) can lower the incoming air temperature.

Zoning by function and occupancy needs (both in plan and section) should be a primary schematic design consideration.

Vertical stacks may need to be integrated with HVAC and structural systems to insure effective utilisation of space.

Although stack ventilation will generally work in most climates, climates with large diurnal temperature ranges are ideal.

Attention should be paid to nearby noise sources. Openings can be located to minimise the effect of noise on occupied spaces.

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