What Are the Problems With Synthetic Roof Underlayment?
Synthetic roof underlayment has become popular in recent years due to its durability and lightweight nature, often used as an alternative to traditional felt underlayment. However, despite its advantages, synthetic underlayment has notable challenges and drawbacks. These can include issues with moisture trapping, susceptibility to UV damage, environmental concerns, and even safety hazards during installation. Understanding these problems will help homeowners and contractors make informed choices about whether synthetic underlayment is the right option.
What is Synthetic Roof Underlayment?
Synthetic roof underlayment is a type of barrier layer installed between the roof deck and the final roofing material, designed to offer extra protection against water infiltration and structural damage. Made from polymers like polypropylene or polyethylene, synthetic underlayment has gained favor due to its lightweight, tear-resistant, and mold-resistant properties, offering enhanced protection over traditional felt. Compared to felt, which is thicker and often heavier, synthetic underlayment offers increased flexibility and easier installation.
There are various types of synthetic underlayment, typically categorized by their material composition and durability. Standard synthetic underlayments include woven polypropylene, polyethylene, and rubberized asphalt options, each offering different benefits for different climates and roofing types.
Why is Synthetic Roof Underlayment Popular?
Synthetic underlayment has become a preferred option due to its durability, water resistance, and ease of installation. Its primary advantages include:
- Durability: Unlike felt, synthetic underlayment is highly resistant to tearing, shrinking, and wrinkling. This makes it ideal for areas with heavy wind or fluctuating temperatures.
- Moisture and Mold Resistance: Synthetic materials are less likely to absorb moisture, which reduces the risk of mold growth under the roof.
- Lightweight and Easy Installation: Weighing less than felt underlayment, synthetic underlayment is easier to transport and install, which can reduce labor costs and installation time.
However, these benefits come with notable limitations that we’ll explore in detail.
Problems with Synthetic Roof Underlayment
While synthetic roof underlayment offers several advantages, it also presents challenges that can affect its performance and longevity. Here are the primary issues to consider.
1. Higher Upfront Cost
One of the most common concerns with synthetic underlayment is its higher upfront cost compared to traditional felt. The price per square foot can vary, but synthetic options generally range from $0.15 to $0.50 per square foot, while felt is usually between $0.05 and $0.10. While the durability of synthetic underlayment may offer long-term savings, the initial investment can be substantial, especially for large roofing projects. This cost consideration becomes even more significant when factoring in labor and potential costs for specialized installation.
2. Slipperiness and Safety Hazards
Synthetic underlayment can be slippery, particularly in wet or icy conditions. This creates safety risks for roofers, especially on steep slopes or during installation in rainy weather. Many manufacturers add textured surfaces to reduce this risk, but caution is still essential. Ensuring proper footwear and safety gear can help mitigate these hazards, but synthetic materials remain inherently slick compared to traditional felt.
3. Moisture Trapping and Condensation Risks
One surprising drawback of synthetic underlayment is its potential for moisture trapping. Unlike felt, which absorbs a small amount of moisture and allows gradual release, synthetic underlayment can trap condensation between the roof deck and the underlayment. This trapped moisture can lead to mold, wood rot, and even structural damage over time. Proper ventilation and correct installation techniques are critical to preventing moisture buildup.
For instance, adding roof vents and ensuring adequate airflow can prevent condensation, reducing the risk of moisture-related damage.
4. UV Sensitivity and VOC Emissions
Synthetic underlayment is vulnerable to UV degradation, especially if left exposed for too long before the roof covering is installed. Extended UV exposure can cause synthetic materials to become brittle and lose flexibility, diminishing their protective qualities.
Moreover, synthetic underlayments may release volatile organic compounds (VOCs), including formaldehyde and benzene, especially when exposed to UV rays. These VOCs can affect indoor air quality and pose potential health risks. Installing the roof covering promptly after the underlayment installation is essential to minimize UV exposure and prevent VOC release.
5. Adhesion and Compatibility Issues
Synthetic underlayments may not adhere well to certain roofing materials, particularly if they’re incompatible or if the manufacturer’s guidelines aren’t followed. Adhesion issues can compromise the underlayment’s integrity, reducing its effectiveness as a moisture barrier. Checking compatibility with roofing materials and adhering to installation instructions is critical to avoid these issues.
6. Durability in Extreme Weather Conditions
In regions with extreme temperatures, synthetic underlayment may not perform as well as expected. Intense cold can cause it to become brittle, while high heat may lead to softening or even melting in extreme cases. In climates with heavy snow, hail, or extreme temperature fluctuations, selecting thicker, reinforced synthetic underlayment is recommended to ensure durability.
7. Environmental Impact and VOCs
The environmental impact of synthetic underlayment, from production to disposal, is another concern. Synthetic materials often have a higher carbon footprint during manufacturing and are less biodegradable than felt. Disposal poses a challenge, as most synthetic materials are not recyclable. Additionally, the VOCs released during production and exposure to sunlight contribute to pollution and may affect indoor air quality.
How to Ensure That Synthetic Underlayment Performs Well With Proper Installation Techniques
Correct installation is essential to ensure synthetic underlayment performs well. Here’s a step-by-step approach:
- Preparation: Ensure the roof deck is clean, dry, and free from debris. Choose an underlayment suitable for the specific roof type and slope.
- Proper Ventilation: Install roof vents to allow air circulation, which helps prevent moisture buildup.
- Securing Overlaps and Seams: Overlap each row of underlayment by at least 4 inches, using compatible adhesives or nails to ensure a tight seal.
- Focus on Valleys and Penetrations: Apply extra sealing around areas like chimneys, skylights, and roof valleys where water is more likely to accumulate.
Following these best practices, especially in challenging roof areas, can help mitigate many common issues associated with synthetic underlayment.
How to Choose the Right Type of Synthetic Underlayment
To choose the best synthetic underlayment, consider the following factors:
- Climate: In humid or wet climates, opt for a synthetic underlayment with high moisture resistance. For hotter climates, choose underlayments with UV-resistant coatings.
- Roof Slope: Steeper roofs benefit from textured or high-traction underlayments to improve safety during installation.
- Compatibility with Roofing Material: Ensure the underlayment is compatible with the roof covering, such as asphalt shingles, metal, or tile.
- Manufacturer’s Specifications: Follow the manufacturer’s installation guidelines and understand the warranty coverage.
Selecting the right underlayment according to these criteria can help prevent many of the issues outlined above.
Frequently Asked Questions (FAQ)
How long does synthetic roof underlayment last?
Typically, it lasts 15-25 years, but climate and installation quality can impact its lifespan.
Can synthetic underlayment be left exposed?
Ideally, no. Prolonged exposure to sunlight can degrade it, so covering it with roofing material within 30 days is advisable.
What are the environmental concerns with synthetic underlayment?
Concerns include VOC emissions, high carbon footprint in production, and limited recyclability.
How is synthetic underlayment recycled?
Most synthetic underlayments aren’t easily recyclable, although some facilities may accept polypropylene or polyethylene materials.
Is synthetic underlayment fire-resistant?
Some types have fire-resistant properties, but not all. Check the manufacturer’s specifications.
