Most people are very confused when it comes to the attic ventilation. Many HVAC companies push for installing attic exhaust fans to cool down the attic space in summers. But are these actually necessary?
Ridge vents are those exhaust ports that run along the ridge of your roof. They can be only spotted by a trained eye. They are tiny in size, but they provide ample space for hot air to exhaust from the attic.
Ridge vents work only with proper attic intake vents. For these soffit vents are installed which draw cool air from the outside. Since hot air rises and it exhausts through the ridge vents, the negative pressure thus created in the attic pulls in the cold air from the outside through the soffit vents. This is the most popular passive ventilation method for the attic.
Powered attic fans
Attic fans are used to forcibly exhaust air from the attic. They are useful when there isn’t proper attic ventilation. These fans run using either electricity or solar power.
They are available in many sizes and with many features, and they are usually installed either on the roof or the gable of the attic.
Do I need attic fans along with ridge vents?
If you already have enough ridge vents then attic fans are not recommended. Attic fans consume energy, and they have some downsides. If you can achieve proper attic ventilation passively just using the vents in the attic, that is always better.
However, in many cases achieving ventilation which is enough to cool down an attic during summer days is not possible due to many reasons. The main reason is improper ventilation. Even though proper vents were provided initially when the house was built, these vents could be blocked overtime by insulations or other things that obstruct the free flow of air through the attic. Also storing a lot of items in the attic also can block the natural flow of air.
Gable vents are also not effective if there are no wind movements parallel to the roof during the day. In these cases, it is necessary to install an attic fan to cool down the attic area.
That being said, whether you need an attic fan or ridge vents can only be considered case by case, there is no one definite answer for this question.
Problems with installing attic fans along with ridge vents
Ridge vents act as exhaust ports for hot air. However, if you install a powered attic exhaust fan near a ridge vent the fan will draw outside air through these vents. So instead of circulating air through the attic the fan will simply suck air in through the ridge vents and exhaust it back to the atmosphere without cooling the attic. This is counterproductive as it will reduce even the existing airflow in the attic.
Sucking air in through the ridge vents can also bring in the water when it is raining. This can damage your attic as well as cause the growth of molds.
Depending on how well your ridge vents perform you can decide whether to install an attic fan or not. If you can achieve natural ventilation that is always recommended.