Note: The information and instructions provided are provided as general information and should not be considered specific suggestions for a particular roof.

An important aspect to maintain a house in good condition, and complete the roofing system, are the roof vents. The ventilation installation is a crucial part of the roof design because it allows proper attic ventilation, which can help prevent condensation and premature aging of roofing materials.

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Advantages of adequate roof ventilation

While there are different types of roof vents to choose from, making sure you have the right amount of ventilation inlets and outlets is a central part of the roof design. Proper ventilation of the attic provides numerous advantages to the owner:

• Ventilation helps regulate the temperature of the attic, it also helps regulate the temperature of the rest of the home.
• It helps to avoid the accumulation of humidity in the attic and, in the colder months, this in turn allows to prevent problems of condensation that can affect the materials of the attic space, especially the insulation.
• By preventing the excessive accumulation of heat, adequate ventilation favours energy efficiency at home; therefore, heating costs may be lower.
• It helps to protect the useful life of roofing materials (condensation is one of the main causes of damage to roofing materials, such as asphalt shingles).
• It helps you comply with most local building codes, which often require adequate ventilation of the attic in the apartment.

How to calculate the amount of ventilation needed

Note: The following information contains suggestions for houses with ventilated attics. There are some styles of houses with vaulted ceilings or flat roofs that have ventilation spaces within the roof itself and no attic. The ventilation needs for this type of housing are calculated differently.

The key to achieving adequate ventilation of the roof and attic is the balance: the amount of space you dedicate to the air intake should be equal to the one you leave for the exit, and both should be calculated based on the size of the attic and the roof slope.

To calculate the attic ventilation requirements, you can determine the square footage of the attic floor (width by length) and compare that figure with the total net free space required. The ventilations are rated according to your free space, that is, the amount of space for the air inlet or outlet. In this way, it is easy to calculate how many ventilations you need for your attic, once you have determined your requirements.

If the attic floor has a vapour barrier, you will need a square foot of free space for every 300 square feet of attic floor area (half of that will be used for entry and the other half for exit). If there is no vapor barrier, you must double the amount; that is, you will need one square foot of free space for every 150 square feet of attic floor space (half for entry and half for exit). These are general guidelines; Be sure to check your local building code.

Then, you can begin to choose the style and type of ventilation you prefer for your home.

It is important to remember that it is always better to have excessive air intake than insufficient air outtake, and in many houses the necessary air intake is poorly calculated. Do not worry so much about having too much ventilation inlet; it is better to sin of exaggerated.

The most popular way to ventilate an attic is to take advantage of the buoyancy or natural tendency of warm and humid air to rise, especially when pushed by the cold air below. Houses are naturally filled with warm and humid air daily thanks to human physiology and activities such as cooking and bathing.

To maximise this effect, the ventilation inlets of the house are usually installed in the lower part of the roof (near the eaves), while the ventilation outlets are located in a higher position (near the top), to allow cold air to push hot air out more easily.

Roof vents are the most adequate option

Before beginning to work on the installation of roof vents, the roofer should determine what type of vents your home needs (or which ones you prefer) and how many you will need according to the calculations explained above.

Next, we describe the different types of roof vents, which will vary according to the needs and architectural style of your home, the geography and meteorological patterns of your region, and the structure of the roof.

These are general guidelines, since most manufacturers will offer instructions on how to install ceiling vents in the best way and what measures should be taken to comply with the specifications of the warranty.

Soffit vents are one of the most popular ventilation inlet types: they are easy to install under the roof overhang (known as «soffit»), are generally hidden and provide excellent protection against weather, waste from outside and pests, while allowing air to enter the attic.

The soffit vents are usually made of aluminium or vinyl and are installed in the soffit, the surface under the eaves of the roof. The soffit vents are highlighted by their small slots that provide an open space through which the air can circulate. There are several diverse types and styles of soffit vents. Always remember to check with the manufacturer that the chosen ventilation has enough net free space for your project.

Beyond the type of style chosen, it is essential to keep soffit vents free of debris or accumulated dirt so that air can circulate freely through the slots.

Owners must also make sure that the attic insulation does not block air circulation. Verify that the insulation is collected so that it does not cover the vents or ask the roofer to install vents in the attic to prevent the insulation from covering the edge of the soffit.

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