cooling two-story houses & natural ventilation

Warm air tends to rise and to exit through clerestories, skylights, ridge vents or other upper openings, causing fresher air to enter via lower openings.

Air buoyancy (chimney effect) is the essence of convective or stack ventilation - an important cooling feature in many climates.

Convective ventilation & Fresh Air & breezes

Convective home ventilation can work without breezes - as long as there are temperature differences between indoor and outdoor air.

However, that will not be effective unless the differences are sufficiently high… If they aren't, breezes in the windward size of the house are crucial for convective ventilation.

Image source: Division of Architecture of California Government.

Size and placement of openings

In the absence of breezes, the effectiveness of convective ventilation depends more critically on the placement of openings in the building, and also on their size.

In convective strategies the upper exit windows should be around 50%-100% more large than the entry openings, for higher effectiveness.

Obviously, windows and other openings should be operable by homeowners.

Pay also attention to the height issue: the greater the height/distance between the low entering points and the high located openings, the more effective will be the natural convection.

Upper openings

Upper openings involve roof vents, clerestories, vented skylights, roof ventilators, solar chimneys and other upper convection pathways. All of them can be excellent for expelling hotter air but they may collide with other goals, namely home sealing and insulation in temperate and cold climates.

Roof ridge vents are ideal for convective ventilation in hotter climates. Just pay attention to possible airflow obstructions...

Interior openings

Interior doors shouldn't block the convective airflow and air circulation. Consider high louvers and other openings between rooms, for better air circulation. And do not forget the ways the breezes can be directed into the rooms through louvres and canopies.