What Is Roof Ventilation and Why Is It Important? - Central Homes Roofing
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What Is Roof Ventilation and Why Is It Important?

Inadequate ventilation can cause damage to your roof and attic
Read Time: 5 minutes
Sep 20, 2022

Ventilation plays a major role in keeping both your roof and your home in good condition. Without it, it could be more difficult to keep your home cool in summer. Poor ventilation could also cause a buildup of moisture that could lead to mold and mildew.

What Is Ventilation?

Ventilation is a system that both lets air into and pulls air out of your attic. The idea is to vent hot air that rises into the attic outside and replace it with cooler air. Ventilation requires both intake and exhaust components in order to properly ventilate your home. This is because you can’t send hot air outside without bringing in air to replace it.

Mechanical Ventilation

mechanical ventilation on top of a roof

With mechanical ventilation, it’s important to ensure that the vents are both intake and exhaust vents so that hot air is pumped out but cooler air is also pumped in from the outside. This type of ventilation is required in certain buildings or locations if natural ventilation isn’t enough to enable proper air flow. For example, buildings in areas with little wind may need mechanical ventilation.

Natural Ventilation

an attic window that functions as ventilation

Natural ventilation allows hot air to escape on its own. Because hot air rises and also has higher pressure, it will vent to the outside naturally via any route it can, whether that’s a vent in the roof or a window. Cooler, low-pressure air should automatically move in to take the place of the hot air.

How Much Ventilation Do You Need?

Ventilation should be spaced out throughout the attic to ensure that the entire roof is properly ventilated. Most building codes require that there should be at least 1 foot of ventilation for every 150 square feet of ceiling space under the roof.

Where Should Ventilation Go?

a roof with vents on top and soffit under the overhangs

You’ll need to have ventilation installed both low and high in the attic. High ventilation will usually be vents located in the roof. These let the hot air out. Vents that are low, which can include windows and soffit, are designed to let cool air in from the outside.

What Problems Can Poor Ventilation Cause?

If your ventilation isn’t properly removing the hot air from your attic, then that hot air will remain trapped there. In summer, this can make it both difficult and expensive to cool your home, especially if you live somewhere hot, like Florida. Hot air is also often moist, which means that if it doesn’t get cycled out, mold and mildew can start to form, which can be costly to repair.

Problem #1

Dry Rotting

When moisture gets trapped in the attic, mold, mildew, and fungi can start to grow. Dry rot occurs when fungi start to eat away at the wood. This can compromise the structural integrity of the attic and the roof.

Problem #2

Curling

Curling, which is also known as cupping, or fishmouthing, is another problem that can occur with poor ventilation. Because of the heat building up inside the home, the roofing materials like shingles can start to warp. If you notice that your shingles appear to be curling or otherwise damaged, it could be a sign of poor ventilation.

Problem #3

Increased Energy Bills

a contractor repairing an air conditioner

If the hot air that rises to the attic can’t escape, then it will stay in your house, making the overall indoor temperature warmer. HVAC systems therefore have to work harder to cool down the house, increasing your energy costs. Working harder can also cause your air conditioner to fail more quickly than it would otherwise.

Problem #4

Mold and Mildew

Hot air that gathers in the attic is also typically moist air. If that moisture is trapped inside, it can start to cause mold and mildew to form as well as cause other water damage, which can be costly to fix.

Problem #5

Increased Risk of Roof Damage

Improper ventilation can damage the roof. This means that it’s more susceptible to further damage during bad weather or if something like a tree branch falls on top of the roof. There could also be an increased risk of roof leaks when it rains even if the weather doesn’t cause other damage.

Problem #6

Sagging Roof

The roof deck is meant to support the roof and keep it in place. However, hot, moist air trapped under it that isn’t adequately vented to the outside could also eat away at the roof deck, which could cause your roof to sag or, eventually, even collapse. This is because the roof decking could start rotting or it could become spongy due to the moisture.

Problem #7

Shorter Lifespan

a carpenter working on the roof deck of a roof to replace it

Roofs can typically last for at least a few decades, even with the least long-lasting roofing materials. However, poor ventilation can cause damage that can significantly reduce the roof’s lifespan. By not having enough ventilation in your attic, you could end up not only having to pay for higher energy bills but also to have your roof replaced sooner than expected.

Problem #8

Increased Risk of Pests

Small animals and insects may look for any path they can take to get inside a house. If there’s damage to a roof caused by poor ventilation, then it’s possible for pests to have an easier time getting in.

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