Thermafiber Vs. Fiberglass: A Comprehensive Comparison For Home Insulation

As a homeowner tackling insulation choices, I’ve faced the challenge of picking the right material for my home’s comfort and efficiency. Thermafiber and fiberglass are two popular options, each with unique strengths and weaknesses.

In this article, I’ll share my journey exploring these materials, comparing their performance, cost, and suitability for various projects. You’ll find a detailed breakdown of pros and cons, a comparison table, and my personal experiences to help you decide which insulation fits your needs. My goal is to guide you through this decision with clarity and confidence.

Comparison Table: Thermafiber Vs Fiberglass

Feature	Thermafiber	Fiberglass
Material Composition	Mineral wool made from natural and recycled materials	Glass fibers spun into a cotton candy-like texture
Thermal Performance	R-value of ~4.2–4.6 per inch	R-value of ~2.2–3.8 per inch
Fire Resistance	Non-combustible, withstands over 2,000°F	Non-combustible but melts around 1,100°F
Sound Insulation	Superior sound absorption due to dense structure	Moderate sound absorption, less effective
Moisture Resistance	Hydrophobic, repels water, prevents mold	Can hold moisture, may lead to mold if exposed
Cost	Higher cost, ~$1.20–$2.00 per sq. ft.	Lower cost, ~$0.50–$1.00 per sq. ft.
Installation	Rigid, requires precise cutting, heavier	Flexible, easier to handle and install
Environmental Impact	Made from recycled materials, recyclable	Less sustainable, non-recyclable in most cases
Health and Safety	Minimal dust, safer to handle with PPE	Can cause skin and lung irritation if mishandled

My Experience With Thermafiber

When I decided to insulate my home’s exterior walls, Thermafiber caught my attention for its fire resistance and soundproofing.

Installing it was a bit of a workout—its rigidity meant I had to measure and cut carefully, especially around outlets and corners.

The weight surprised me; it’s denser than I expected, and hauling batts to my attic was no small feat.

But once in place, the results were impressive.

My home felt quieter, with less noise from the nearby highway, and the temperature stayed stable even during cold snaps.

The peace of mind from its fire resistance was a bonus, especially since my neighborhood has strict fire codes. However, the cost was a hurdle. I spent about 30% more than I would have on a budget-friendly alternative, which made me second-guess my choice initially.

Still, the long-term energy savings and durability have started to balance out the upfront expense. For sound-sensitive areas like my home office or bedroom, Thermafiber was a clear winner, but I wouldn’t use it everywhere due to the price and installation effort.

Pros Of Thermafiber

Exceptional Fire Resistance: Thermafiber, a type of mineral wool, is non-combustible and can withstand temperatures exceeding 2,000°F, making it a top choice for fire safety. I’ve seen it used in commercial buildings where fire codes are strict, giving peace of mind in high-risk areas like attics or near fireplaces.
Superior Sound Insulation: Its dense, fibrous structure absorbs sound waves effectively, reducing noise transfer between rooms. When I insulated my home office with Thermafiber, the difference was noticeable—street noise dropped significantly, creating a quieter workspace.

Moisture Resistance: Thermafiber is hydrophobic, meaning it repels water and prevents mold or mildew growth. This is a game-changer in humid climates or basements, where dampness can be an issue. I’ve never had to worry about mold in areas insulated with it.
Eco-Friendly Composition: Made from natural and recycled materials, Thermafiber is sustainable and recyclable. Knowing my insulation choice aligns with environmental values feels good, especially since it reduces waste without sacrificing performance.
Thermal Efficiency: With an R-value of around 4.2–4.6 per inch, Thermafiber outperforms many competitors in thermal resistance. In my home, it’s kept rooms consistently comfortable, reducing energy bills noticeably during winter months.

Pest Resistance: Its inorganic structure deters rodents and insects, a huge plus for long-term durability. Unlike some materials, I’ve never found signs of nesting or damage in Thermafiber-insulated areas.
Versatility for Exterior Use: Thermafiber’s rigid panels can be used as exterior insulation, supporting cladding and promoting drying in rainscreen systems. This makes it ideal for modern building designs prioritizing vapor permeability.

Cons Of Thermafiber

Higher Cost: Thermafiber is pricier, typically costing $1.20–$2.00 per square foot, which can strain budgets for large projects. When I priced out insulating my entire home, the cost was a significant factor compared to cheaper alternatives.

Rigid and Heavy: Its dense, rigid nature makes it harder to handle and cut precisely, especially in irregular spaces. During installation, I found it less forgiving than other materials, requiring more effort to fit snugly.
Limited Availability: Thermafiber isn’t as widely available as other insulation types at local hardware stores. I had to order it online for one project, which added lead time and shipping costs.
Installation Challenges: The rigidity and weight demand careful handling and sometimes specialized tools. I struggled with cutting it to fit around pipes, which slowed down my DIY project significantly.

Dust During Installation: While safer than some alternatives, cutting Thermafiber can produce dust, requiring masks and gloves. I found this mildly irritating during a long installation session, though it’s manageable with proper precautions.
Not Ideal for All Climates: In extremely dry climates, its moisture-repelling properties are less critical, potentially making the higher cost less justified. I considered this when planning insulation for a vacation home in a desert region.

My Experience With Fiberglass

Fiberglass was my first choice when I started insulating my home, mainly because it was affordable and easy to find.

Installing batts in my garage was a breeze—I could cut and fit them with minimal effort, and the lightweight material didn’t tax my energy.

The process felt forgiving, especially for a DIY novice like me. I noticed a decent improvement in temperature control, keeping the space usable even in summer heat.

However, the itchiness from handling it was a downside; I underestimated the need for protective gear.

In my basement, I had to be meticulous with vapor barriers to prevent moisture issues, which added complexity. The soundproofing was underwhelming in my home theater, where I could still hear outside noise. Overall, fiberglass worked well for budget-conscious projects, but I wouldn’t rely on it for high-performance needs like fire resistance or noise reduction.

Pros Of Fiberglass

Cost-Effective: Fiberglass is budget-friendly, typically costing $0.50–$1.00 per square foot, making it accessible for large projects. When I insulated my garage, fiberglass kept my expenses low without compromising basic performance.
Easy to Install: Its flexibility and lightweight nature make it a DIYer’s dream. I found it easy to stuff into wall cavities and around obstacles like pipes, saving me time during installation.

Wide Availability: Fiberglass is stocked at nearly every hardware store, from big-box retailers to local shops. I never had trouble finding it, even for last-minute projects.
Good Thermal Performance: With an R-value of 2.2–3.8 per inch, fiberglass provides decent insulation for most homes. It kept my garage comfortable enough for year-round use without breaking the bank.
Non-Combustible: While not as fire-resistant as mineral wool, unfaced fiberglass doesn’t catch fire easily, offering reasonable safety. I felt confident using it in less critical areas like storage spaces.

Flexible Applications: Fiberglass comes in batts, rolls, and loose-fill, adapting to various spaces. I used loose-fill fiberglass in my attic to fill gaps, which was a quick and effective solution.
Established Track Record: Fiberglass has been a go-to insulation for decades, with proven reliability. I appreciated knowing it’s a tried-and-true option backed by years of use in homes worldwide.

Cons Of Fiberglass

Lower Fire Resistance: Fiberglass melts around 1,100°F, which is less robust than mineral wool. This made me hesitant to use it in high-risk areas like near my fireplace.

Moisture Issues: Fiberglass can hold moisture if exposed, potentially leading to mold growth. In my basement, I had to ensure proper vapor barriers to avoid this risk.
Health Concerns: Handling fiberglass can cause skin irritation and respiratory issues if not done carefully. I got itchy after installing it without gloves, a lesson I learned the hard way.
Sound Insulation Limitations: Fiberglass is less effective at blocking sound compared to denser materials. In my home theater, it didn’t reduce noise as much as I’d hoped.

Degradation Over Time: Fiberglass can settle or break down, reducing its effectiveness. I noticed this in an older part of my home where the insulation had compacted slightly.
Environmental Impact: Fiberglass isn’t as eco-friendly, often containing non-recyclable materials. This bothered me when I considered the long-term sustainability of my home.
Pest Attraction: While not a magnet, fiberglass can attract rodents in unfinished spaces like attics. I found minor nesting in an old fiberglass-insulated shed, which was frustrating.

Comparison With Other Brands

Rockwool vs. Thermafiber: Rockwool, another mineral wool, shares Thermafiber’s fire resistance and soundproofing but is often slightly cheaper, around $1.00–$1.50 per square foot. I found Rockwool easier to source locally, but Thermafiber’s higher R-value (4.2–4.6 vs. Rockwool’s 4.0–4.3) gave it a slight edge for thermal efficiency.
Rockwool vs. Fiberglass: Rockwool outperforms fiberglass in fire resistance (2,000°F vs. 1,100°F) and sound absorption due to its denser structure. However, fiberglass is more flexible and cheaper, making it better for quick DIY jobs. I preferred Rockwool for my bedroom but used fiberglass in less critical areas.
Cellulose vs. Fiberglass: Cellulose, made from recycled paper, offers similar R-values (3.1–3.8) to fiberglass but is more eco-friendly. It’s prone to settling, though, which I noticed in an older home where it lost effectiveness over time. Fiberglass was easier to install for me.

Cellulose vs. Thermafiber: Cellulose is less expensive than Thermafiber but lacks its fire resistance and moisture-repelling properties. I considered cellulose for my attic but chose Thermafiber for its durability and safety in exterior walls.
Spray Foam vs. Fiberglass: Spray foam provides superior R-values (6.0–7.0 per inch) and air sealing but costs $2.00–$3.00 per square foot. I used spray foam in tight spaces but stuck with fiberglass for larger areas to save money.
Spray Foam vs. Thermafiber: Spray foam excels in air sealing but lacks Thermafiber’s fire resistance and soundproofing. For my home office, Thermafiber’s noise reduction was more valuable than spray foam’s higher R-value.

Polyiso vs. Both: Polyisocyanurate (polyiso) foam boards offer R-values up to 6.5 per inch and act as vapor barriers. However, they’re pricier and less fire-resistant than Thermafiber. I found polyiso less practical for DIY wall insulation compared to fiberglass or Thermafiber.

Frequently Asked Questions (FAQ)

Does Thermafiber Insulation Have Fiberglass?

No, Thermafiber is mineral wool, made from natural and recycled materials like volcanic rock, not glass fibers like fiberglass.

Is There Better Insulation Than Fiberglass?

Yes, options like Thermafiber, Rockwool, or spray foam often outperform fiberglass in fire resistance, soundproofing, or R-value, depending on your needs.

What Are The Disadvantages Of Mineral Wool Insulation?

Mineral wool, like Thermafiber, is pricier, heavier, harder to install, and less widely available than fiberglass, with potential dust during cutting.

Is Thermafiber Good For Exterior Walls?

Yes, Thermafiber is excellent for exterior walls due to its fire resistance, moisture repellency, and ability to support cladding in rainscreen systems.

Conclusion: For Thermafiber And Fiberglass

Choosing between Thermafiber and fiberglass depends on your priorities. If you value fire safety, soundproofing, and sustainability, Thermafiber is worth the higher cost, especially for critical areas like exterior walls or noise-sensitive rooms. Its durability and eco-friendly nature make it a long-term investment. However, if budget and ease of installation are your focus, fiberglass is a reliable, affordable choice for less demanding spaces like garages or attics. I’ve used both successfully, and my advice is to match the material to your project’s needs. You can’t go wrong by weighing cost against performance for your home’s unique requirements.