Your house needs to breathe. The attic is where all the heat from the house builds up and is crucial for the air vapors to be expelled from the house to prevent mold. If the air is not expelled from the attic, it will cause problems such prematurely deteriorating shingles from a hotter roof decking. Mold, any moisture can be a problem with no ventilation.
In warm climates the roofs ventilation will help to keep the house cool, saving money on cooling costs.
In cold climates the roofs ventilation will help prevent ice and water dams. It does this by allowing the attic to remain cool so that it doesn't melt the snow on top of the roof and allow the water to refreeze at the eave, causing the dam.
A ridge vent works best when paired with a vented soffit. The air flowing up through the soffit and out through the ridge allows for a vertical ventilation. The only opposing way to ventilate would be to have a horizontal draft by using gable vents. Gable vents are vents through the wall on each side of the attic that allow a natural breeze through the attic. It is not recommended to have both a vertical draft and horizontal, because they will cancel each other out.
Most shingle manufacturers warranties are void if the roof is not vented properly. Due to the over cooking roof temperatures.
There are many different brands and styles of ridge vent.
The older style ridge vents are made of aluminum. These older style ridge vents have an outside nail line, leaving the nails exposed. These exposed nails will rust and wiggle themselves out of the plywood due to expansion and contraction along with being exposed to the elements. Once these nails start to raise out, the aluminum vent will start to raise off the roof from the wind blowing them up. This is a very common cause of a leaking roof and we are doing many ridge vent replacements that involve removing old aluminum style ridge vents.
The cheaper stuff is a rolled mesh type material. This stuff can often give a wavy appearance if not nailed down properly.
The best ridge vent for the stormy northeast regions are a GAF Snow Country ridge vent that is available in four foot vinyl sections. These have a hidden nail line which leave no exposed fasteners to rust.
Snow Country ridge vents are topped off with a cap shingle nailed over the vent. These caps are hand nailed with 2 ½” roofing nails which helps to prevent any shingles from blowing off.
There are many different styles and brands of cap shingles. GAF uses 2 different lines, Seal-A-Ridge and Timbertex. Seal-A-Ridge cap shingles come with a double layer of shingle protection while Timbertex are more heavy duty with a third layer of asphalt added. The Timbertex cap shingles also give a more raised profile appearance and are the go to look on bigger roofs with more roofing sections.
For aesthetic purposes the ridge vent can be cut back one to three feet from the ends of the gables. The new school roofers will mostly install the vent all the way from gable end to gable end for a more clean look.
Ridge vent leaks are easy to detect. To find a leaky ridge vent all you have to do is go in your attic and shine a flashlight on the rafters. If you can see a dark stain all around the ridge vent, that usually means it is leaking. Usually a drip trail can be followed down a rafter to the area where the leak is entering the house.
The easiest way to deal with a leaking ridge vent would just be to call a roofing contractor and have it replaced. Sometimes a ridge vent is ready to be replaced when the roofs shingles still have a couple years left in them. Replacing ridge vents can normally be accomplished within a few hours.
Sometimes a ridge vent is not required on a ridge. You want to install the amount of ridge vent that is called for in the houses blueprints. Architects design the ridge vents with the amount of ventilation needed for the house in mind. Any ridge vent added or subtracted from the houses plan can affect the (word for air suction in house). It is perfectly normal not to install ridge vents on smaller dormers or on garages.