Thursday, July 15, 2010

Mechanical Ventilation

Natural ventilation can be a key element of cooling strategies in many climates. Mechanical ventilation can also be part of cooling strategies (that's the case of the ceiling fans), but they involve also a rather different type of ventilation to exhaust stale...

More than just opening windows

In its simplest version natural ventilation is opening windows and doors, to benefit from breezes. But natural ventilation - cross and stack ventilation - can be part of a more elaborate approach for cooling our homes, involving features like home design, landscape, placement and size of openings, etc

Cross ventilation

When people open windows in opposite sides of the house to cool the indoor temperatures, they are using cross ventilation.

Stack (Convective) Ventilation: the «Chimney Effect

Natural stack ventilation (also called convective ventilation) uses a physics natural fact: the chimney effect or air buoyancy...

In natural stack ventilation, the warmer indoor air rises up from lower living areas and escapes through the upper openings of the building, causing cold air infiltration through windows or other lower openings…

climates and natural ventilation

Natural ventilation loses much of its power in hot-humid climates. Unlike mechanical air-conditioning, natural ventilation doesn’t reduce the humidity of incoming air, making the cooling process rather ineffective during periods of high humidity.

Higher humidity conditions, requires greater air-speeds and greater ventilation to provide comfort. And the breezes and shaded spots may not provide those pre-conditions.

If natural ventilation can’t provide significant comfort, and you live in hot climates, you may try a closed building-air-conditioning approach for some parts of the house

Deflecting the wind: Wing Walls and casement windows

Wing walls are vertical panels placed next to windows to intercept and direct the colder breezes into the house, via open windows or other openings. They are specially useful to deflect breezes, when they don't blow in the more convenient pattern (see image).

Casement windows can work as wing walls. Just have into account the way the casement windows open relatively to the dominant breezes, in order to direct the wind into the home. Casement hinges can be located on the left-hand side or on the right-hand side, taking into account the dominant direction of the breezes...

Mechanical ventilation

Mechanical ventilation involves 1) ceiling fans and other assisted-fan ventilation, but also 2) exhaust fan ventilation (simple kitchen exhaust fans or bathroom exhaust fans, and the more sophisticated HRV and ERV ventilation).

While natural ventilation or ceiling fans are part of cooling strategies, the exhaust ventilation systems main goal is to exhaust stale air, replacing it with fresh air (which is particularly important in cold and temperate climates, in tightly insulated homes).

Natural ventilation, cracks and air leakage

Air leaks and gaps were traditional ways of supplying fresh air to homes, in cold climates. 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 losses, and since many modern well insulated and airtight houses do not provide that source of outside air, mechanical ventilation becomes crucial for reasons that have nothing to do with cooling goals.

Ventilation & Health

In many cold climates or even in some mild ones, gaps and leaks in the walls or next to windows and doors are a source of contaminants such as formaldehyde or radon, which can cause health problems; besides, these same gaps can also be a source of moisture and lead to mold growth and cause damages…

1 comment:

  1. Ventilation is one of the most important drivers of health and hygiene factors of your bathroom. Using good quality bathroom ventilation fans ensures that you get a bathroom that is free from moisture and stinky smells. Also, selecting the right bathroom fan can improve the decor of your bathroom by an order of magnitude.



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