Is Roofing Felt Breathable? (Addressing Ventilation Concerns)

When it comes to roofing, ventilation is an important factor to consider. If your roof doesn’t have enough ventilation, it can get wet and have other problems that can cost a lot to fix.

So, when it comes to the roofing felt, one of the most common questions is whether or not it is breathable.

Is roofing felt breathable?

Roofing felt is semi-breathable. It allows some air to pass through it, but not as much as a fully breathable material would. This helps to reduce condensation buildup under the roofing material, but it may not fully prevent moisture-related problems.

The semi-breathable nature of roofing felt can help to reduce heat buildup in the attic space, but it may not be as effective as fully breathable material.

Roofing felt is made from a combination of organic materials, such as asphalt and paper, which have some porous properties.

This allows some air to circulate through the material, reducing condensation buildup.

However, the breathability of roofing felt is limited, and it may not be able to prevent moisture-related problems to the same extent as a fully breathable material, especially during winter and snow seasons.

Despite this, roofing felt can still help to reduce heat buildup in the attic space and extend the life of the roofing system.

What are the benefits of using breathable roofing felt?

Prevents moisture buildup

Breathable roofing felt allows air to circulate through it, reducing the amount of moisture that can build up under the roofing material.

The idea is the more breathable a material is, the less likely it will form condensation.

This helps to keep the roof deck dry, which can prevent mold growth, rot, and other moisture-related problems.

Extends the life of the roofing system

By preventing moisture buildup, breathable roofing felt can help to extend the life of the roofing system.

Moisture can cause damage to the roof deck, framing, and insulation, but breathable roofing felt helps to keep these components dry and in good condition.

Reduces heat buildup

Breathable roofing felt can also help to reduce heat buildup in the attic space.

By allowing air to circulate, roofing felt can help to keep the attic cooler and reduce the amount of heat that is transferred into the home, making it more comfortable.

Improves indoor air quality

By preventing moisture buildup, breathable roofing felt can also help to improve indoor air quality.

Mold and other moisture-related problems can release harmful substances into the air, but breathable roofing felt helps to prevent these problems from occurring.

What are the drawbacks of using a breathable roofing felt?

Cost

Breathable roofing felt is typically more expensive than non-breathable roofing materials. This can make it a more costly option for those who are looking for an affordable roofing solution.

Limited durability

Breathable roofing felt is made from organic materials, such as asphalt and paper, which can be prone to degradation over time.

This can reduce the durability of the roofing felt, making it less effective at preventing moisture buildup and other problems.

Limited breathability

While breathable roofing felt does allow air to circulate through it, the breathability of the material is limited.

This can mean that it may not be as effective at preventing moisture buildup and other problems as a fully breathable material.

Installation difficulty

Installing breathable roofing felt can be more challenging than installing other roofing materials.

You have to make sure there’s about 1 to 2 cm of slack as it droops and use nails on the battens.

Felt has to be cut to fit the shape of the roof and sealed properly to keep water out.

What is the best breathable roofing felt?

  • Permeability: A good breathable felt should allow air and moisture to pass through while preventing rainwater from entering the roof space.
  • Durability: The breathable felt should be made from high-quality materials that are durable and long-lasting.
  • Resistance to weathering: The felt should be able to withstand harsh weather conditions such as wind, rain, and extreme temperatures.
  • Compatibility: Make sure the breathable felt is compatible with your roofing system, including the tiles or slates you plan to use.
  • Weight: Consider the weight of the felt and make sure it is suitable for your roof structure.
  • Cost: Make sure the felt fits within your budget and compare different options to find the best value for your money.
  • Manufacturers reputation: Choose a reputable manufacturer with a good track record in producing high-quality breathable felts.

How does a breathable roofing felt help with ventilation?

Breathable roofing felt helps with ventilation by allowing air to circulate through it, reducing the amount of moisture that can build up under the roofing material.

By reducing moisture buildup, breathable roofing felt helps to keep the roof deck and attic space dry, which can improve indoor air quality and reduce the risk of mold growth, rot, and other moisture-related problems.

Breathable roofing felt is made from a combination of organic materials, such as asphalt and paper, which have some porous properties.

This allows air to circulate through the material, reducing the amount of moisture that can build up under the roofing material.

Additionally, by reducing moisture buildup, breathable roofing felt can help to reduce heat buildup in the attic space, making it more comfortable and extending the life of the roofing system.

How to install breathable roofing felt?

Step-by-step guide for breather membrane installation:

  1. Roll out the felt horizontal and tack it to the rafters, leaving a 10 to 15-millimeter sag between each rafter. This will direct any water away from the structure.
  2. Make sure that the printed side of the membrane is facing out.
  3. Fit the battens to the rafters. Before fitting, check the size and gauge to ensure they are correct for the tile choice as this can affect the weather tightness of the roof. Battens should be fixed to the rafters at centers no more than 600 millimeters apart.
  4. Use nails with a minimum of 40-millimeter penetration into the rafter. A nail length of 65 millimeters is recommended.
  5. Starting at the lower edge of the roof, nail the battens into place directly into the rafter centers. Each pattern should overhang at the verge by 30 to 50 millimeters to allow for the correct installation of the verge units.
  6. Continue up the roof, overlapping adjoining felt by at least 100 millimeters.
  7. Peel back the strip protecting the tape on the underside of the felt and secure the felt in place.
  8. Where possible, the lap of the membrane should coincide with the closest tiling or slating baton. The membrane should always be laid to sit five to thirty millimeters short of the ridge battens.

Factors to consider when choosing a breathable roof felt

When choosing a breathable roof felt, it’s important to think about how well it breathes, how long it lasts, how much it weighs, and how much it costs.

Breathability is important for reducing moisture buildup and improving indoor air quality.

Durability ensures a long-lasting roofing material.

The weight of the felt affects installation ease and durability.

And the cost is a consideration, as breathable roof felt can be more expensive than other roofing materials but may save money in the long run due to its longevity.

Are all roof felt breathable?

No, not all roof felt is breathable. Some roofing felt is made to be waterproof and not let any air or water through, while others are made to be semi-permeable and let some air through.

What is the difference between breathable and non-breathable roofing felt?

Breathable roofing felt is usually made of a material that lets air and water pass through, such as a non-woven polymer.

This type of felt is often made from a combination of synthetic fibers, such as polypropylene, and other breathable materials that allow for air and moisture to circulate.

Non-breathable roofing felt is made from a waterproof material that does not allow air or moisture to pass through.

This type of felt is typically made of asphalt or similar waterproof material that is designed to protect against water damage and prevent the buildup of moisture inside the roof space.

Some non-breathable roofing felts are made from a combination of asphalt and other synthetic materials that help to increase their strength and durability.

What materials are used in breathable roofing felt?

  • Polyethylene (PE) film: This is a lightweight and flexible material that is used as a base for the roofing felt. It allows moisture to escape from the roof space and prevents condensation from forming.
  • Polypropylene (PP) nonwoven: This is a breathable material that is used to provide additional strength and stability to the roofing felt. It helps to prevent the roofing felt from tearing or breaking during installation.
  • Bitumen: This is a waterproof material that is used to provide an extra layer of protection against water damage. Bitumen is typically applied to the underside of the roofing felt to prevent water from penetrating the roof space.
  • Adhesives: Breathable roofing felt is typically held together with a combination of adhesives, including hot melt and pressure-sensitive adhesives. These adhesives provide a strong and durable bond that helps to prevent the roofing felt from separating or tearing over time.
  • Core polyester layer: This provides additional strength and stability to the roofing felt, helping to prevent it from tearing or breaking during installation. The polyester layer also adds to the breathability of the roofing felt, allowing moisture to escape and helping to prevent condensation from forming.

Is breathable roofing felt more effective than non-breathable roofing felt?

Some people think that roofing felt that can breathe is better than roofing felt that can’t breathe, but this depends on the roof application and the results that are wanted.

Breathable roofing felt lets water escape from the roof so that condensation and dampness don’t form.

This can result in a more comfortable and healthy indoor environment and can help extend the lifespan of the roofing material.

This type of felt can also help to reduce the risk of damage to the roof structure and insulation, which can lead to costly repairs.

But roofing felt that doesn’t breathe can be better in some situations where a lot of water resistance is needed.

For example, non-breathable roofing felt can be used in areas with high rainfall or in coastal regions where the roof is exposed to high levels of moisture.

Does breathable roofing felt protect against moisture and condensation?

Yes, breathable roofing felt helps protect against moisture and condensation to some extent. It allows the escape of water vapor from inside the building, reducing the risk of condensation and mold growth.

The permeable felt acts as a barrier, stopping water from getting into the roof while letting water vapor escape.

However, it is important to note that breathable roofing felt is not a guarantee against moisture and condensation, and proper ventilation is still necessary to ensure a dry and healthy indoor environment.

Is breathable roofing felt waterproof?

No, breathable roofing felt is not completely waterproof. It is made to be water-resistant, which means that it can keep some water from getting into the roof structure.

But it’s not meant to be completely waterproof because its main job is to let water vapor escape from the building to stop condensation and mold growth.

Breathable roofing felt is usually put on top of other roofing materials, like tiles or shingles, to make the roof completely waterproof.

Even if your roof has breathable roofing felt, it still needs to be checked and maintained regularly to make sure it stays in good shape and to find any possible water leaks.

How long does breathable roofing felt last?

Breathable roof felts typically last for about 20–25 years, or potentially a lifetime.

This can depend on things like the quality of the felt, the type of roofing material used, and how well the roof is taken care of and maintained.

Breathable roof felts are made to last in bad weather and protect against damage from rain, wind, and UV rays.

Most people will just change out the felt once they replace their roofs.

Keep in mind that factors such as improper installation or improper ventilation can reduce the lifespan of the felt and lead to issues with mold and mildew growth, roof rot, and other problems.

Do I need to vent a roof with breathable felt?

Yes, a roof with breathable felt still needs ventilation. Breathable roofing felt helps air flow and reduces the chance of condensation, but it is not enough to get rid of the need for good ventilation.

Without proper ventilation, heat and moisture can still build up in the attic, leading to problems like mold growth and damage to the roof structure.

Alternatives you can use to ventilate your roof

Ridge Vent

This type of ventilation is installed at the peak of the roof and runs along the ridge line. It allows air to escape through the top of the roof, helping to regulate temperature and moisture levels inside the attic.

Gable Vents

Gable vents are installed on the gable ends of the roof, which is the triangular section that extends from the eaves to the ridge. They help provide an opening for hot air to escape, which helps regulate the temperature inside the attic.

Soffit Vents

Soffit vents are installed in the soffit or under-eave area of the roof. They provide an opening for air to flow into the attic, which helps to regulate temperature and moisture levels.

Roof Turbines

Roof turbines are spinning vents installed on the roof. They work by using wind power to spin a turbine, which draws hot air out of the attic and helps to regulate the temperature and moisture levels.

Roof Louvers

Roof louvers are vents that are installed on the roof. They are designed to provide an opening for hot air to escape, which helps regulate the temperature inside the attic.

Dormer vents

These are vents installed in the dormer, a structure that projects from the sloping roof and allows air to escape through the top of the roof.

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Logan
Author: Logan

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