The Basics of Roof Ventilation

Roof ventilation is one of the most important aspects of keeping your home comfortable and making your roof last longer. Based on basic laws of convection, warm air rises. With that in mind, you must determine the best way to release that hot air from your roof.

roof venting

In the same way that you need consistent airflow throughout your home, your roof also requires airflow—understanding why airflow matters and how to improve it is an essential part of home ownership.

Why Roof Ventilation Matters

One of the most important aspects of roof ventilation is releasing hot, humid air from your roof into the air around your home. Humidity measures the amount of moisture in the air, so when humidity builds up in your attic, the moisture level in the air increases.

Most ceilings aren’t sealed perfectly, which allows warm air to flow from your living quarters into the attic. When the insulation and lumber in the attic encounter this moist, humid air, the possibility for damage increases. Not only does this allow lumber to rot, but mold and mildew can grow on the surfaces in your attic.

Your climate will largely determine how much roofing ventilation you need. Most building codes require that you have one square foot of roof venting for every 300 square feet of roofing. This is a minimum standard. You can never have too much roof ventilation.

Roof ventilation doesn’t only impact your home during warmer months. When winter comes, a poorly ventilated attic may get so hot that it melts the snow on your roof. Since the eaves of your home remain cold, ice dams form along the edge of your roof. If your roof has asphalt shingles, these ice dams allow water to pool and eventually penetrate the surface of your shingles.

Proper ventilation can add years to your roof’s lifespan depending on the type of roofing finish. If the bottom layers of an asphalt shingle roof face too much heat, the shingles may crack. Proper ventilation helps reduce the likelihood that asphalt shingles suffer damage.

What Type of Roof Ventilation is Best?

Within the world of roof ventilation, you have multiple options. Roof ventilation comes in two types: active and passive.

  1. Active ventilation relies on a system of mechanical fans in the attic of your home. These fans work together to pull fresh air from outside your home while simultaneously pushing warm, stagnant air out of your attic.
  2. Passive ventilation does not involve fans, allowing air to flow naturally in and out of your attic or upper-level crawlspace. While passive ventilation is more energy efficient, it is not as effective in many climates.

Depending on the type of roof ventilation you choose and the number of vents you have installed, roofing ventilation installation costs anywhere between $300 and $2,000.

The type of roof vents that you install on your home will determine which type of roof ventilation you have. If you want active ventilation, you will choose between turbine vents (also called “whirly birds “), solar vents, powered vents, or ridge vents with a baffle. Baffles are plastic flaps that open and close, allowing air to flow in and out of the ridge vent.

Passive vents include static vents and ridge vents without baffles. Unfortunately, the absence of baffles on passive ridge vents makes it easy for bugs, debris, water, snow, and other elements to get into your home.

Roofing contractors can also cut passive ventilation into the side of your home. One of the most popular types of passive ventilation is gable vents. Roofing contractors cut these vents into the side of your home just below the peak of your roof. They rely on wind hitting both sides of your home, creating a constant flow of air going in and out of the upper portion of your home.

Signs of Faulty Roof Ventilation

You must know how to determine the effectiveness of your roof’s current ventilation. Not only does doing so reduce the likelihood of bacterial growth in your attic, but it can also lead to lower utility bills.

You don’t have to be a roofing contractor to determine that you need increased ventilation in your roof. One of the most effective ways to assess ventilation needs is to go into your attic. If the air is humid and feels “sticky,” you should consider installing additional roofing ventilation.

You can also recognize the need for improved ventilation during winter months. After a snowstorm, go outside and compare your roof to your neighbors’ roofs. If their roofs are free from snow but you still have snow on your roof, you probably need to improve the ventilation in your roof.

Having adequate ventilation in your roof is an integral part of extending the lifespan of your roof. If you notice increased temperatures in your attic, snow buildup on your roof, or any other signs of poor ventilation, you should contact a roofing contractor immediately.