Insulation Showdown: Fiberglass vs. Foam Board

Choosing insulation for your home comes down to performance, cost, and suitability for your climate. Fiberglass and foam board are two popular options, each with unique strengths. Fiberglass is affordable and easy to install, while foam board offers superior thermal resistance and moisture protection - especially important in humid climates like Florida. Here's a quick breakdown:

• Fiberglass: Lower cost (~$0.90/sq ft), R-value of 2.2–3.8 per inch, ideal for interior spaces like walls and attics.
• Foam Board: Higher cost (~$1.50/sq ft), R-value of 3.6–8.0 per inch, excels in moisture-prone areas like basements and foundations.

Key takeaway: Fiberglass suits budget-conscious projects, while foam board delivers better energy efficiency and durability in challenging environments. For Florida homes, combining both materials can balance cost and performance.

Quick Comparison

Factor	Fiberglass	Foam Board
Cost per sq ft	~$0.90	~$1.50
R-Value per inch	2.2–3.8	3.6–8.0
Moisture Resistance	Low	High
Best Applications	Interior walls, attics	Basements, exterior walls

Pro Tip: Foam board's higher R-value can reduce energy bills over time, offsetting its initial cost. For large or complex projects, professional installation ensures optimal results.

Foam vs Fiberglass Insulation

Cost Analysis: Fiberglass vs. Foam Board

When it comes to insulation, understanding the cost differences between fiberglass and foam board helps highlight the trade-offs between initial expenses and long-term benefits. Let’s break down both the upfront and ongoing costs of these two materials.

Material and Installation Costs

Fiberglass insulation stands out for its lower upfront cost, with materials averaging around $0.90 per square foot. On the other hand, foam board insulation is priced higher, averaging about $1.50 per square foot - almost twice as expensive.

For a standard 1,000-square-foot project, this translates to:

• Fiberglass: approximately $900 in material costs
• Foam board: approximately $1,500 in material costs

While foam board comes with a higher price tag, it provides nearly double the R-value per inch compared to fiberglass. For example, achieving an R-21 rating would require 5.5 inches of fiberglass but only 3.5 inches of foam board.

When it comes to installation, labor costs for both materials are generally comparable. However, foam board may require slightly more effort due to the precision needed for cutting and fitting. If you analyze cost efficiency based on R-value, foam board’s superior thermal resistance can make its higher price more justifiable.

These upfront costs are just one part of the equation. To fully assess value, it’s important to consider long-term energy savings.

Long-Term Savings Analysis

The real financial impact of insulation often lies in its ability to reduce energy bills over time. Foam board’s higher R-value and air-sealing capabilities can lead to noticeable savings on heating and cooling costs, especially in regions with extreme temperatures . For homeowners in Florida, for example, foam board’s moisture resistance combined with its thermal efficiency can significantly cut air conditioning costs, offsetting its higher initial price.

According to industry data, the extra investment in foam board insulation typically pays off through energy savings within 5 to 10 years, depending on factors like local energy rates, climate, and the quality of the installation. Fiberglass, while cheaper upfront, often requires more material to reach the same level of energy efficiency, which can extend the payback period .

Some U.S. states and utility companies also offer rebates or incentives for upgrading insulation, which can help reduce the initial cost of premium options like foam board.

Energy Performance and R-Value Analysis

Understanding R-Value

R-value is a key metric for gauging an insulation material's ability to resist heat flow. Essentially, the higher the R-value, the better the insulation is at keeping your home warm in the winter and cool in the summer. In Florida, where air conditioning works overtime, insulation with a high R-value helps maintain comfortable indoor temperatures and reduces energy bills by easing the strain on your AC system.

R-Value Performance: Fiberglass vs. Foam Board

When comparing fiberglass and foam board insulation, the difference in R-value is striking. Fiberglass batts typically range from 2.2 to 3.8 per inch, while foam board insulation offers higher thermal resistance. Here's how the numbers stack up for foam board options:

• Expanded Polystyrene (EPS): R-value of 3.6 to 4.0 per inch
• Extruded Polystyrene (XPS): R-value of 4.5 to 5.0 per inch
• Polyisocyanurate (Polyiso): R-value of 5.5 to 8.0 per inch

To make it easier to compare, here’s a quick breakdown:

Insulation Material	R-Value per Inch	Best Application
Fiberglass Batts	2.2 – 3.8	Interior walls, attics
Fiberglass Loose-fill	2.2 – 4.3	Attic spaces, irregular areas
EPS Foam Board	3.6 – 4.0	Cost-effective exterior applications
XPS Foam Board	4.5 – 5.0	Moisture-prone areas, foundations
Polyiso Foam Board	5.5 – 8.0	Premium exterior walls, roofing

The higher R-values of foam board insulation are a game-changer, especially in situations where space is limited - like retrofitting older homes or insulating narrow wall cavities. This added efficiency makes foam board a strong contender in thermal performance.

Impact on Energy Bills and Home Comfort

Insulation with a higher R-value significantly reduces heat transfer through your home's exterior, which means your air conditioning system doesn't have to work as hard. In Florida, where summer temperatures can soar, this translates to more consistent indoor temperatures and noticeable savings on energy bills.

Foam board insulation, with its superior thermal resistance, also helps minimize temperature fluctuations inside your home. And when installed correctly, it delivers peak performance. For Florida homeowners, where humidity and heavy rainfall are common, foam board’s moisture resistance combined with its high R-value makes it a standout choice for both comfort and energy efficiency.

Durability and Moisture Performance

When it comes to maintaining long-term comfort in humid climates, durability and moisture resistance are just as important as cost and energy efficiency.

Lifespan: Fiberglass vs. Foam Board

Both fiberglass and foam board insulation can last up to 100 years if kept dry and undisturbed. However, their actual lifespan often depends on environmental conditions and physical stress. Fiberglass insulation can lose its effectiveness when compressed or exposed to moisture - something that’s particularly problematic in places like Florida attics. Foam board, on the other hand, resists moisture better but is prone to cracking or breaking under mechanical stress. When properly installed, foam board maintains its R-value and structure even in humid conditions.

Moisture and Mold Resistance

Florida’s high humidity creates unique challenges for insulation. Foam board insulation, with its closed-cell design, minimizes water absorption and reduces the chances of mold and mildew. This makes it a solid choice for basements, crawl spaces, and exterior walls in damp areas. Fiberglass, however, can absorb and trap moisture if not paired with an effective vapor barrier, creating an environment where mold can thrive. Without proper moisture protection, fiberglass remains vulnerable in humid settings.

Fire Safety and Building Code Considerations

Fire safety is another critical factor when selecting insulation. Fiberglass insulation is naturally non-combustible, offering strong fire resistance that typically meets U.S. residential building codes. This makes it a reliable option for interior spaces where fire safety is a priority. Foam board, however, isn’t inherently fire-resistant and requires a thermal barrier - like drywall - to meet code requirements in occupied areas.

Safety Feature	Fiberglass Insulation	Foam Board Insulation
Fire Resistance	Naturally non-combustible	Requires a thermal barrier for fire protection
Mold Risk	Higher risk if exposed to moisture	Low risk due to moisture resistance
Code Compliance	Meets most residential requirements	May need additional fire protection measures

In Florida, where stricter building codes have been implemented following hurricane damage, foam board’s fire safety requirements can add complexity and cost to installations. Whether you choose fiberglass or foam board, regular inspections are essential. For fiberglass, check for signs of moisture, compression, or mold. For foam board, look for cracks or water intrusion. These steps ensure your insulation continues to perform as expected while keeping future maintenance costs in check.

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Installation Methods and Best Applications

Knowing how to properly install different types of insulation can help you make informed decisions that align with your project needs and budget. Each material has its own strengths, costs, and performance characteristics.

How to Install Fiberglass Insulation

Fiberglass insulation is a popular choice for DIY enthusiasts because it's relatively easy to handle. The process involves measuring the wall cavities, cutting the fiberglass batts to size using a sharp utility knife, and fitting them snugly between the studs. It's important to avoid compressing the material, as this can reduce its insulating ability (R-value). Always wear proper safety gear, such as gloves, goggles, and a mask, to protect yourself from fiberglass particles.

Fiberglass batts are designed to match standard stud spacing, typically 15 inches or 23 inches wide, which simplifies installation in most residential spaces. While small projects, like insulating a single room, can often be completed over a weekend, larger tasks - such as insulating an entire attic - may demand more time and effort. The key is to preserve the material's fluffy texture for optimal performance.

How to Install Foam Board Insulation

Installing foam board insulation requires careful planning and precision. Start by measuring the area and cutting rigid foam sheets (usually 4-by-8 feet) to fit the space. Use tools like a utility knife or a saw for accurate cuts. Depending on the project, foam boards can be attached using adhesives, mechanical fasteners, or a combination of both.

To ensure maximum efficiency, seal all seams and edges with tape or spray foam. This step prevents thermal bridging and enhances the insulation's performance. Foam boards can be applied in various ways - loosely laid, fastened to walls, or adhered to smooth surfaces. Their modular design allows for continuous coverage, but proper planning is essential to minimize waste and ensure a snug fit. Foam board's moisture resistance and high R-value make it especially effective in challenging environments.

Best Applications for Each Material

Choosing the right insulation for specific areas of your home can maximize efficiency and cost-effectiveness. Fiberglass insulation works well in interior spaces like wall cavities, attics, and ceilings, where moisture exposure is minimal. Its affordability and ease of installation make it a go-to choice for large areas like living rooms or bedrooms. In Florida's humid climate, fiberglass can perform effectively in above-grade interior walls when paired with a vapor barrier.

On the other hand, foam board insulation shines in areas that are prone to moisture. Its higher R-value per inch and moisture-resistant properties make it ideal for basement walls, exterior walls, and foundations. It’s particularly effective for below-grade installations and exterior continuous insulation, which are common in Florida homes.

Application Area	Best Choice	Key Reason
Interior walls (above-grade)	Fiberglass	Cost-effective and easy to install
Basement walls	Foam board	Superior moisture resistance
Exterior walls	Foam board	Higher R-value and continuous coverage
Attics and ceilings	Fiberglass	Affordable for large areas
Foundations	Foam board	Essential moisture protection

For Florida's climate, which demands both energy efficiency and moisture resistance, a hybrid approach can be a smart solution. Use foam board in moisture-prone areas like basements and foundations, while relying on fiberglass for interior spaces to strike a balance between cost and performance.

For larger or more complex projects, or when compliance with building codes is necessary - such as when foam board requires a thermal barrier for fire safety - hiring a professional can save time and ensure the job is done correctly.

Side-by-Side Comparison: Fiberglass vs. Foam Board

Selecting the right insulation becomes easier when you can directly compare the essential factors. This detailed breakdown highlights the differences between fiberglass and foam board insulation, helping you make the best choice based on your needs and budget.

Complete Comparison Table

Here’s a side-by-side look at the key performance factors:

Factor	Fiberglass Insulation	Foam Board Insulation
Material Cost	~$0.90 per sq ft	~$1.50 per sq ft
R-Value (per inch)	Less than R-4	Approximately R-6 (polyiso)
Thickness for R-21	5.5 inches	3.5 inches
Moisture Resistance	Poor – can trap moisture	Excellent – highly resistant
Fire Safety	Non-combustible, naturally fire-resistant	Requires thermal barrier for code compliance
Installation Difficulty	Easy DIY, flexible design	More challenging, often requires professional
Durability	Can compress and degrade over time	Rigid, maintains performance
Noise Reduction	Moderate sound dampening	High sound insulation
Expected Lifespan	Up to 100 years (if undamaged)	Up to 100 years (if undamaged)
Best Applications	Interior walls, attics, ceilings	Basements, exterior walls, foundations
Mold Risk	Higher in damp conditions	Low due to moisture resistance

This table provides a quick summary of the main differences between these two insulation types.

Foam board insulation, while 67% more expensive per square foot, requires less thickness to achieve the same thermal performance as fiberglass. With an R-value nearly double that of fiberglass per inch, foam board offers superior energy efficiency, which can lead to better temperature regulation and lower energy bills over time. This makes it especially beneficial in climates like Florida, where heat and humidity are constant concerns.

Moisture resistance is another area where foam board outshines fiberglass. Foam board is highly resistant to moisture, making it a top choice for basements, exterior walls, and foundations. In contrast, fiberglass can trap moisture, increasing the risk of mold growth. For DIY enthusiasts, fiberglass is easier to handle and install, while foam board may require professional expertise for proper application.

When it comes to fire safety, fiberglass has a natural edge since it’s non-combustible. Foam board, however, needs additional protection, such as a thermal barrier like drywall, to meet building safety codes.

For Florida homeowners, foam board is a smart investment in areas prone to moisture, such as basements and foundations. Meanwhile, fiberglass remains a cost-effective and practical solution for interior spaces where moisture isn’t a concern and ease of installation is a priority.

Final Recommendations and Professional Help

Key Points Summary

When deciding between fiberglass and foam board insulation, the choice boils down to your home's specific needs, budget, and conditions. Fiberglass is a more affordable option at approximately $0.90 per square foot and provides fire-resistant insulation, making it a solid choice for interior spaces. On the other hand, foam board, priced higher at around $1.50 per square foot, offers better R-value and moisture resistance, which makes it ideal for exterior applications. However, the effectiveness of either insulation type largely depends on how well it’s installed.

In Florida, many homes benefit from using a mix of both types. Fiberglass works well in interior areas where fire resistance is a priority, while foam board is better suited for exteriors and spaces prone to moisture. Additionally, Florida's building codes often require higher R-values or continuous insulation, and foam board can meet these requirements more effectively than fiberglass. Because foam board requires precise fitting and sealing, professional installation is highly recommended to ensure optimal performance.

Choosing the right insulation type - and ensuring it’s installed correctly - is key to improving your home's energy efficiency and comfort.

Bayshore Exteriors: Professional Installation Services

Proper installation is critical to unlocking the full benefits of your chosen insulation. Bayshore Exteriors specializes in expert consultation and professional installation for insulation and siding projects, helping Florida homeowners find durable, energy-efficient solutions tailored to their unique needs.

Their team ensures your project complies with local building codes and enhances long-term energy savings. This is especially important for foam board insulation, where accurate fitting and sealing are essential for peak performance. Bayshore Exteriors also understands how insulation integrates with features like James Hardie siding to create a complete thermal barrier that boosts efficiency.

Beyond insulation, Bayshore Exteriors offers custom exterior remodeling and finishing services. This holistic approach ensures all exterior systems work together to improve energy efficiency, durability, and curb appeal. If you're unsure which insulation type suits your home best, their consulting services provide expert advice to help you make well-informed decisions, balancing performance, cost, and long-term value.

FAQs

Are the long-term energy savings of foam board insulation worth its higher upfront cost?

Foam board insulation might come with a higher upfront price tag compared to fiberglass, but its ability to save energy in the long run can make it a smart choice. Thanks to its excellent thermal resistance (R-value), foam board helps minimize energy loss, which can lead to noticeable reductions in heating and cooling expenses over time.

What sets foam board apart is its durability and resistance to moisture. This means it maintains its performance for years, even in challenging conditions. While the initial investment may seem steep, the savings on energy bills and lower maintenance costs over its lifespan can make it a practical and budget-friendly option for many homeowners.

What challenges might come up when installing foam board insulation, and why consider professional help?

Installing foam board insulation comes with its own set of challenges, often requiring a skilled hand to get it right. For instance, achieving a tight seal is crucial to prevent air leaks, and cutting the boards to fit irregular spaces can be tricky. Securing the boards properly is just as important to avoid any shifting over time. On top of that, foam boards often need additional measures, like adding a vapor barrier or taping the seams, to improve energy efficiency and guard against moisture problems.

If you're not familiar with the process, these tasks can quickly become overwhelming and eat up a lot of time. Bringing in a professional can take the guesswork out of the equation, ensuring the insulation is installed correctly for optimal performance and lasting durability.

Can using both fiberglass and foam board insulation together improve energy efficiency and protect against moisture?

Combining fiberglass and foam board insulation can improve energy efficiency and help resist moisture when done right. Foam board acts as a sturdy barrier, blocking air leaks and keeping moisture out, while fiberglass works by trapping air in its fibers to provide strong thermal insulation. Together, they create a well-rounded system that enhances overall performance.

That said, the way you install them plays a huge role in achieving these benefits. If you're thinking about using both, it’s a good idea to consult a professional to figure out the best setup for your home’s unique requirements.