natural home ventilation

Contaminants such as formaldehyde or radon can accumulate in poorly ventilated homes, causing health problems; and moisture can lead to mold growth and cause damages in your home… Ventilation is a key element to solve this problems. Besides, natural ventilation is also a cooling strategy that may reduce significantly your air conditioning bills.

Natural ventilation

Mechanical ventilation is absolutely necessary in well insulated houses, in most climates. Only mechanical ventilation may provide a constant and reliable source of fresh air. And only mechanical ventilation can solve some problems with indoor air sources of moisture.

But there are also many situations, and some climate conditions, where natural ventilation is an advantageous strategy to get fresh air or to cooling your house, reducing air conditioning bills.

Natural ventilation, cracks and air leakage

Air leaks and gaps were traditional ways of supplying fresh air to homes. They acted like vent openings, contributing to the ventilation needs. But since these gaps and sources of air leaks are also a source of heating and cooling wastes, and since many well insulated and airtight houses have eradicated them, natural ventilation (and mechanical ventilation) have become truly indispensable.

Natural ventilation

In its essence, natural ventilation is opening windows and doors, taking into account temperatures, wind breezes and the most favorable moments.

But there are some fundamental mechanisms that you should know, namely, what specialists call natural cross ventilation and natural stack ventilation. Pay also attention to wing walls...

Climate considerations

Natural ventilation isn't an universal solution. In hot and humid climates it should be avoided. And also in colder climates, in most days. Natural ventilation relies on outdoor temperatures and winds, and since they are rarely favorable in some climates, natural ventilation only sporadically can be applied in these same climates.

Natural ventilation is mainly a solution for moderate climates, or for hot dry climates.

Natural Cross ventilation

When people open windows in opposite sides of the house, they are using cross ventilation, that is, they are using high and low pressure zones created by wind and breezes to draw fresh air into the house.

In natural cross ventilation, the wind (breezes) enters in a window (or another vent, in an appropriate side of the building) bringing fresh air and pulling staled air to exit through opposite openings of the house. The image below (from the Division of Architecture of California Government) illustrates the process.

Natural Cross Ventilation

Obviously, you should pay attention to the wind flowing patterns and to the placement of windows, doors and other openings. In ideal terms, the house should be located and oriented to benefit from the dominant wind breezes and their patterns.

Natural Stack Ventilation: the «Chimney Effect»

Natural stack ventilation uses the chimney effect, that is, the tendency of heated air to rise as in a chimney.

In natural stack ventilation, the warmer indoor air rises up from living areas through the attic or other top part of the building, reducing the pressure in lower parts of living rooms, allowing cold air to infiltrate through strategically placed open spaces (windows or other openings)…

This technique can be applied by designing an exit window (or other opening) in a strategically high located place of the building/room, and another window/vent/opening in a low location, where cool air will enter. The image below, from the Division of Architecture of California Government, illustrates this mechanism.

Natural Stack Ventilation

Wing Walls

Wing walls are vertical panels placed next too windows (perpendicular to the wall on the windward side of the building) to drive the colder breezes in the intended paths.

Creating more favorable conditions

Windbreaks, large and strategically located windows, operable windows and ceiling fans and other fans can be used in cross and stack ventilation. They may create or accentuate the conditions that make natural ventilation possible.