natural ventilation, cooling and home design

Natural ventilation is based on fresh air entering through openings in the walls (on the windward side of the home). That fresh air (associated to breezes or shaded areas) will help to push warmer air out of the house through the other side of the home (cross ventilation) or through roof vents or other upper openings (convective ventilation).

The effectiveness of natural ventilation is highly associated with the design of the house - including floor-plans, home orientation, narrow buildings or the location and size of windows, louvers and clerestories…

Other elements of that effectiveness, that should be conveniently studied, include the pattern of breezes, climate and landscape. See: Ventilation and breezesAir movement and types of ventilation
Air movement is the key element of passive cooling, either in the form of 1) cross ventilation, 2) convective ventilation or 3) mechanical ventilation.
Cross ventilation is based on fresh air entering in one side of the house, pushing warmer inside air out of the building through openings in the opposite side. Convective ventilation involves fresh air entering the home by lower openings, while warmer air rises and goes out through upper openings (often in the second floor of the house).
Mechanical ventilation: fan-assisted natural ventilation is especially suitable for people cooling and an excellent complement to natural ventilation.

Types of windows and openings

For natural ventilation purposes, prefer casement windows and louvres (to other types of windows). Casement windows can deflect the breezes when their patterns aren’t the more advantageous, channeling the wind into the supply openings.

Directing The breezes into the house

The way breezes are directed into the living space may depend on the position of elements like louvres and canopies.

A canopy over a window will direct the entering air upward (Image 3), but if that canopy has a gap between it and the wall, that will make the breezes to gain a downward direction (Image 4). A louvered sunshade (a sunshade with several gaps) will produce a large downward-upward air movement (Image 5). The image below depicts these effects, and also the fact that louvres can also deflect the breezes downward (Image 1) or upward (Image 2), depending on their alignment.

Narrow Homes

It is difficult to distribute fresh air to all the rooms of a large building.

In hot climates, a narrow and relatively small house will be much easier to cool with natural ventilation (or any other type of cooling).

If you live in a hot climate and are building a new home, bet on a narrow building with an open-floor design: a narrow home without obstructions between its two sides. It will make natural ventilation more efficient.

Air circulation and air mixing

Openings between rooms should be considered carefully in natural ventilation strategies. Transom windows, grills, canopies and louvers are important elements to complete the air circuit through the home.

To maximize the air mixing, orient windows properly, and offset them from each other. Also do not forget to minimize the impact of obstructions to airflow within the rooms.

Exhaust openings should be located high enough, to maximize convective cooling (see: Natural (convective) Ventilation).