Does a roof have to be vented?

Author: Florian Graham  |  Last update: Sunday, August 10, 2025

Proper roof ventilation is essential to protect your home from moisture damage and keep your roofing materials from premature failure.

What happens if a roof is not vented?

Poor ventilation can damage shingles by causing extreme roof temperatures, water damage to roof decking, and more. That's why it's important to be alert to the state of your roof's exterior.

What is the rule for roof ventilation?

To ensure ventilation is achieved throughout the whole roof structure, there should be a vented space of at least 50mm provided between each of the rafters between the top of the insulation and the underside of the roof covering.

Do roof shingles need to breathe?

Having adequate balance of intake and exhaust venting is the most important thing a property manager or owner can do to get the optimum life from asphalt shingles. An abundance of either vent (intake or exhaust) does not make up for a lack of the other.

Does a roof without an attic need to be vented?

What About Homes That Don't Have Attics or Crawlspaces? Many homes have vaulted ceilings without an attic space. Homes without attics or crawlspaces are surprisingly common, including in low-slope or flat-roof homes. However, just because there is no attic space doesn't mean you don't need ventilation.

How Does Proper Attic Ventilation Protect my Roof?

Can you insulate a non vented roof?

Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons: to provide an unvented, conditioned space for locating HVAC equipment in the attic, and/or to provide a continuous thermal barrier for designs that have complex ...

What happens if you don't vent your roof in a mobile home?

Without proper roof ventilation, you allow the attic to remain at a high temperature. This can damage and crack your shingles well before they should be showing signs of damage. Go with the flow. Roof vents create proper air flow, which reduces moisture that can build up inside an attic.

Should all roofs have ventilation?

Our trained team of roofing experts are often asked if roof vents are entirely necessary. The short answer is, yes!

Do you need to vent an attic if you spray foam it?

Unconditioned Attics: In unconditioned attics, where spray foam is installed on the attic floor or between joists, ventilation is still essential. Systems like ridge vents, soffit vents, or gable vents allow air to flow, which helps control moisture and heat.

What if my roof doesn't have a ridge vent?

Most of the estimators mention the option of a ridge vent installed at the top of the roof, some mention it in passing and don't really push it too hard one way or the other, and others, while not exactly insisting it be installed, say that without the installation of a ridge vent, the attic would receive inadequate ...

What is the roof ventilation rule?

A universally accepted guideline for roof ventilation is the 1/150 ventilation rule. According to this rule, a roof must have ventilation that is at least one square foot for every 150 square feet of attic or crawl space. A minimum of 13.3 square feet of ventilation is needed for a 2,000-square-foot attic.

Is ventilation a legal requirement?

The building regulations ventilation requirements stipulate that each habitable room should have a system in place for it, although that 'system' might simply be a door or window. Alternatively, in rooms without such openings, a mechanical extract ventilation system can be used.

How to tell if your roof is properly vented?

Here are some of the big signs you don't have proper roof ventilation:
  1. Visible Exterior Damage From Moisture. ...
  2. Excessive Temperatures Inside the Home. ...
  3. Moisture in the Attic. ...
  4. Ice Dams During the Winter. ...
  5. Visible Damage from Moisture Inside the Home.

How do you ventilate an existing roof?

These include:
  1. Ridge vents. These are installed along the ridge at the very top of the roof, where the two sides of the roof meet. ...
  2. Box vents. As their name suggests, box vents are box-shaped, and they are installed near the top of the roof. ...
  3. Soffit vents. ...
  4. Gable vents. ...
  5. Electric vents.

Does every house have a roof vent?

Most building codes us the 1/300 rule for minimum residential attic ventilation recommendations. This means that for every 300 square feet of enclosed attic space, 1 square foot of ventilation is required – with half at the upper portion (exhaust vents) and half in the lower portion (intake vents).

Why are attic fans not used anymore?

Why are attic fans not used anymore? Due to inefficiencies in relying on existing attic vents for air intake, attic fans have lost popularity. These vents often aren't designed for this purpose, resulting in inadequate replacement air supply.

Is there a downside to spray foam attic?

Due to its quick and straightforward installation process and affordable pricing, spray foam insulation is quickly becoming a popular product. However, there is a chance that the insulation in this product will start to shrink over time, which will lessen its insulating capabilities.

What is an unvented roof?

Unvented roof assemblies are becoming an increasingly common construction alternative to traditional vented roofs. They are designed without ventilation openings, and the attic is conditioned like the rest of the living space.

What happens if you don't put vents in your roof?

Roofing System Deterioration

Not only can excessive heat and moisture ruin roof decking, but it can also reduce the life of the underlayment and shingles themselves. Cracking shingles or premature loss of granules can be signs of improper roof ventilation.

What are the rules for roof ventilation?

In the case of a mono pitch or lean-to roof 10mm eaves ventilation is required together with 5mm ridge or top edge ventilation. If the roof pitch is 15 degrees or less then 25mm eaves ventilation is required.

What is the proper vent for a roof?

Effective ventilation in an unfinished attic usually includes intake vents down low along the soffits, and exhaust vents up high at the peak or roof ridge. This allows for a continuous flow of air through the space.

Does a roof need to be vented if there is no attic?

If an air space exists between the ceiling and the roof, then yes. If there is no air space between the ceiling and the roof, then no. The vents are to provide air movement within that air space, equalizing temperature, humidity, and pressure.

Do plumbing vents have to go through the roof?

They extend through the roof to allow sewer gases to escape from your home safely. Without proper venting, these gases can build up inside your home, leading to foul odors, health hazards, and even dangerous levels of methane gas.

Why do mobile homes have vents on the roof?

Roof vents are essential for improving indoor air quality in a manufactured home. Stale air, odors, and pollutants can accumulate indoors, affecting the health and comfort of the residents. Roof vents facilitate the exchange of indoor and outdoor air, helping to vent out stale air and bring in fresh air.

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