Active Ventilation vs Passive Ventilation

To understand which is recommended, you have to first understand which each type of ventilation is.

Active ventilation actively draws air our of the attic.  There are several types of vents that can do this.

1. Solar vents — The most expensive, but as soon as light hits the solar cell, it spins a fan, drawing air out of the attic.  Many of these are rated for up to 1500 square feet of ventilation with just one solar vent.
2. Power vents — Usually hooked up to electricity, power vents are triggered to go on when a temperature and/or humidity sensor notices the temperature or humidity are too high.  These levels are typically set by the homeowner.
3. Turbine vents (Recommended) — more popular in years past, turbine vents spin and draw air out of the attic even with a gentle breeze.  They are very effective and few parts that can go bad since they spin on a ball bearing system.

Passive ventilation relies on convection.  Heat rises, and if you have a balanced system where the intake is equal to or greater than the exhaust ventilation, this type of system can work quite well.  There are a few different types of passive ventilation that works.

1. Ridge vent — probably the most popular of vents that have come out in the last few decades.  There are high, medium and low profile vents that allow heat to escape at varying rates.  Unfortunately many contractors do not calculate the amount of ventilation that goes on different parts of a house and rather than using solid measurements and calculations, they use a cookie cutter approach which often doesn’t work for the homeowner.
2. Slant back, Pod, or Turtle vents — The most common type of vent that require placement of several vents on the roof at strategic locations.

Houses that have had problems with ventilation, or more specifically moisture in the attic space, are great candidates for active ventilation.  Active ventilation, while more expensive, can move air like no other type of ventilation if calculated well and installed to meet ventilation standards.  However, passive ventilation may be sufficient on houses with conditioned attic spaces.