The Physics of Roof ventilation – The Bernoulli Effect
In order to obtain optimal ventilation in a roof, we use methods of natural ventilation, which actually use the same principals seen in an airplane wing to produce the “lift” needed for flight.
This doesn’t mean your roof is going to fly off, but instead, it means we use an effect called the Bernoulli principle to help with our ventilation. The effect is named after Daniel Bernoulli who first discovered this concept in hydrodynamics, back in 1738 (long before the inventions of human flight). The Bernoulli principle states that an increase in the speed of a fluid will also cause a decrease in its pressure. This concept can be derived from Newton’s 2nd law of motion.
The effect is used to properly ventilate your attic. It is a system of intake and exhaust. In a normal ridge vent, the air is drawn into your eaves at the bottom of the roof -and since hot air rises- it is then expelled out the ridge vent at the top. This basic system uses the thermal effect to release hot air and moisture. In addition to that, though, our natural ventilation system uses the wind (Bernoulli effect) to help the process.
We use the wind by using a Baffled FilterVent, which uses an external baffle along the entire length of the ridge. The baffle works as a barrier from the high-pressure force in the wind, which causes a small channel of low-pressure along the ridge. This low-pressure channel along the ridge actually causes it to “lift” the air out of the attic to keep it circulating.
Similar to an airplane in that the high-pressure air flows underneath the wing and the low-pressure air shoots across the top, causing it to “lift” the plane’s wing.
Without this baffle, there would be nothing but high-pressure winds hitting the ridge and the system could only rely on the thermal effect to move air through the attic. By creating this channel of low pressure, it creates a natural vacuum with the wind to keep your roof healthy.
