There are currently several types of ventilation systems available for your roof, all of which have their advantages and disadvantages.
Before deciding the type of vent to use in the roof of your home, it is essential to understand why roof vents are necessary in the first place and, after that, to understand how each type of roof vent works.
Roofing contractors consider ridge vents to be the most preferred option when ventilating the roof of any home. Ridge vents are less invasive than other vent types while remaining the most cost-effective and energy-efficient compared to other roof vent types.
With all the different types of vents currently available on the market and their different applications and possible combinations for intake and exhaust vents, it is essential to understand how each type of vent works and how the exhaust vents work in conjunction with the different intake vents.
Why is Ventilation Important?
Ventilation is crucial in ensuring that your home performs at its best in terms of breathability, air circulation, and safety.
Hot air can rise out of the building if the roof has adequate venting while simultaneously removing moisture.
As a result, the roof’s insulation remains dry, the airflow within the home remains efficient, and the temperature of the building remains at a comfortable constant.
In older buildings, ventilation was not as much of a concern because these buildings are not airtight, so that the air could escape at multiple points throughout the building envelope.
Contemporary homes, conversely, have become so well-sealed and insulated that hot air often has nowhere to escape. As a result, the hot air escapes through the roof through properly placed vents to prevent moisture and humidity build-up within the home.
A home without good attic ventilation can cause many undesirable effects to the attic space itself, the roof, the rest of the house, and as a result, may have an effect on your lifestyle within the home.
Poorly ventilated buildings will have a poor quality of indoor air due to the air in the attic not having anywhere to go, resulting in dead, stale air.
Due to the rising of hot air, the upper floors of your home may become warmer than desired. As a result of this, air-conditioning systems may become overburdened and overworked in an attempt to keep the home’s temperature at a constant level.
Because the moisture in the warm air has nowhere to escape, a build-up of moisture may occur in the attic space, potentially damaging internal structures in the long term. During cold periods, ice dams can occur, which is never ideal. Another concern is the potential for dry rot to occur in the sheathing of the roof.
Advantages of Ridge Vents
Ridge vents are the most efficient option for ventilating a roof. Warranties applicable to roofing manufacturers require at least one square foot of ventilation for every 150sqf of attic space.
However, when using a ridge system, the requirement drops to one square foot of ventilation for every 300sqf of attic space, which means a significant difference in efficiency between the two systems.
The primary objective of a ridge vent is to allow for the unobstructed exit of heat, hot air, odors, and moisture which you would have otherwise trapped in the attic.
The main advantage that a ridge vent has over other types of vents is its location. The air moves from a point lower down in the roof and exits at the highest possible point, being the peak.
Another significant advantage that a ridge vent has over other vent types is its length. A ridge vent usually runs along the entire length of the roof’s ridge, creating the largest possible ventilation opening compared to other types of vent systems.
The design of ridge vents allows wind to pull air out of the attic as it passes over the ridge. Fresh air is simultaneously drawn into the underside of the vent, thus creating the most efficient type of air circulation. The ridge vent essentially creates a vacuum in the attic, which is extremely good for circulation purposes.
In terms of aesthetics, ridge vents can blend seamlessly into the roofline. No unsightly vents are poking up above the roofline, and the vent is almost invisible to passersby at ground level.
Combining this type of exhaust vent with a soffit intake vent is highly advisable for ridge vents to function optimally.
Exhaust vs Intake Vents
Air intake and exhaust play an equally important role in ensuring that a roof is sufficiently ventilated. Understanding how these two concepts work together is essential before choosing the correct roof vent system for your home.
To ensure proper ventilation for your roof, installing both intake and exhaust ventilation is extremely important. While this may not always be possible due to the structure of some roofs, it is advisable whenever possible.
The intake vents allow the cool air to push out the hot and stagnant air from the structure, with this hot and stagnant air leaving through the exhaust vents.
Because hot air rises, and hot air contains moisture, you must be able to remove this from the attic space. If it cannot leave through the exhaust vents, the air will become stagnant, eventually leading to mildew and mold within the attic space.
For this reason, exhaust vents are placed as high as possible on the roof, ensuring the most efficient exit of air from the roof structure.
However, hot air will not leave the roof structure easily without being pushed out by cooler air where intake vents come into the equation. The cool air moves into the attic through intake vents which are naturally lower than the exhaust vents.
Because the hot air rises and the cooler air enters underneath the hot air, the hot air pushes upwards and out of the exhaust vents if the exhaust vents have sufficient surface area. This is why ridge vents are particularly advantageous due to their high surface area.
Exhaust Vent Types
Ridge vents are the most common exhaust vents in roofing projects across the country. This is due to their numerous inherent advantages, as mentioned above. Mainly, their position at the peak of the roof allows the hottest air to escape while allowing for the most surface area to expel the most air.
If used in conjunction with an intake vent such as a soffit vent, ridge vents can create the best possible vertical ventilation. Vertical ventilation refers to the abovementioned concept of the cold air entering from the bottom and pushing the hot air out the top of the roof.
Off Ridge Vents
Off ridge vents are installed close to the roof’s ridge, not too far from where a ridge vent would be. However, this type of vent is closer to a standard box vent in its construction.
These vents are less effective than ridge vents because they do not sit as high up on the roof of the building, and they have a smaller surface area through which to expel air. At around 4 feet in length, off ridge vents can be helpful when the length of the roof’s ridgeline is small, for example, a house with a complex roof system with a series of shorter roof ridges.
Box vents are used in a larger number than other vents, and the installation of these involves cutting a hole in the roof for the vent to sit over it. One or two box vents are not sufficient to ventilate a roof, so you must install a high number of these to ventilate the roof effectively.
Powered Attic Vents
This type of vent consists of an electrically propelled fan that assists in pulling the stale air out of the attic. These are also available in a solar-powered variation.
Turbines, aka whirlybirds, are a type of vent with aluminum blades inside of aluminum covering that rotates using the wind outside the house to pull air from inside the house.
Intake Vent Types
Intake vents are equally essential to exhaust vents in that the two types work in conjunction to achieve the best ventilation for your roof.
Soffit vents are the most popular intake vent type in use, which is for a good reason. These are most often used in conjunction with a ridge vent to ensure the most effective ventilation. If this type of vent is a possible option in the design of the house, it will most likely be the first option chosen.
Soffit vents are installed directly on the eaves, underneath the roof overhang. Small holes allow cool air to flow into the attic space, pushing hot air through the exhaust vent.
Continuous soffit vents wrap around the entire overhang of the building, whereas individual soffit vents are placed approximately six feet apart on the ceiling of the roof overhang. The continuous soffit is naturally more effective as it possesses a larger surface area to allow air intake.
Gable vents do not use vertical ventilation, such as in soffit vents, rendering them slightly less effective on the whole. Gable vents allow air to pass from one side of the attic to the other.
Over Fascia Vents
This is a new type of intake vent used in instances where there are not sufficiently sized eaves to fit the usual soffit type vent. A fascia vent is placed at the top of the fascia board and gutter and directly underneath the first row of shingles.
This vent allows air to enter where the wind hits the roof. This type of vent is particularly small, and so the potential for air intake is relatively small. I would only recommend using this type of vent in instances where you cannot use soffit vents.
Drip Edge Vents
This type of vent is similar to a fascia vent in design and effectiveness. They are designed to take air intake head-on while allowing for the cool air to be pulled up the interior wall of the roof toward the exhaust vent at the peak of the roof.
Like fascia vents, drip edge vents can be used when a soffit vent is not applicable.
What Does a Ridge Vent Cost?
Ridge vent installation can cost between $400 and $500 on an existing roof. However, ridge vents installed while the roof is being built may decrease the price by a significant amount.
Overall, a ridge vent is preferable for a roof ventilation system for several reasons, as illustrated above. Combined with a soffit intake vent, the ridge vent will provide the best value for money, as well as the effectiveness required for a well-functioning roof system.
A good understanding of how air moves naturally will allow you to make the best-informed decision regarding your roofing ventilation.