At Bossline Spray Foam, we specialize in closed-cell spray foam insulation. While we believe in the benefits of our product, we’re not here to push it as the only option. Instead, we want to give you a straightforward, no-nonsense comparison of the four main types of insulation used in Ontario homes: closed-cell spray foam, fiberglass, rock wool (mineral wool), and blown-in cellulose.
Open-cell spray foam is another type of spray foam insulation, but it differs from closed-cell foam in its lower density and lower R-value. While it can offer some sound-dampening qualities, it is less effective for soundproofing compared to materials like rock wool.
Open-cell foam is also less resistant to moisture and provides a less complete air barrier than closed-cell spray foam, which is the focus of our comparison.
Choosing the right insulation can significantly impact your home’s energy efficiency, comfort, and long-term value. Our goal is to share what we’ve learned from years in the construction industry, so you can make the best decision for your home, whether or not that choice involves spray foam.
What Each Insulation Type Is and How It Works
Closed-Cell Spray Foam Insulation
Closed-cell spray foam is a high-density insulation material that expands on application to form a rigid, impermeable barrier. Unlike open-cell foam, closed-cell foam provides a higher R-value per inch, excellent air and moisture sealing, and adds structural strength to the building.
This type of insulation is ideal for areas where space is limited, like basements, exterior walls, and attics, and for creating a continuous air barrier that prevents leaks and drafts. It must be installed by certified professionals to ensure proper application and safety.
Fiberglass Insulation
Fiberglass is one of the most commonly used insulation materials and comes in two forms: batts and blown-in. Batts are pre-cut sections that fit between wall studs and ceiling joists, while blown-in fiberglass is loose-fill insulation sprayed into attics and other hard-to-reach spaces.
While it’s often marketed as a DIY-friendly option, installing fiberglass correctly can be challenging. Taping and sealing the vapor barrier requires precision to prevent air leaks and moisture problems, which, if not done properly, can lead to serious issues like mold and reduced insulation effectiveness.
Rock Wool (Mineral Wool) Insulation
Rock wool is made from natural stone and recycled materials, offering excellent fire resistance and soundproofing capabilities. It is denser than fiberglass and holds its shape well, which makes it ideal for areas where soundproofing is needed, such as between floors or in multi-family buildings.
Rock wool also provides good thermal insulation and moisture resistance but is more costly and challenging to install compared to fiberglass, often requiring professional help for best results.
Blown-In Cellulose Insulation
Blown-in cellulose insulation is made from recycled paper products treated with fire retardants, making it an eco-friendly option. It is typically installed by blowing the material into attics, wall cavities, and other enclosed spaces.
Cellulose has good thermal properties and is more effective than fiberglass at filling irregular spaces. However, it can settle over time, reducing its effectiveness, and doesn’t provide an air or moisture barrier like spray foam.
Key Comparison Factors
R-Value per Inch and Space Efficiency
R-value is a measure of how well an insulation material resists heat flow. The higher the R-value, the better the material insulates. Different materials provide different R-values per inch, which influences how thick the insulation needs to be to achieve the desired energy efficiency.
- Closed-Cell Spray Foam: Offers the highest R-value per inch at 5 to 6.2, making it the most space-efficient option. It is important to note that this R-value is indicative of long term thermal resistance, not simply the initial value.
- Fiberglass: Has an R-value of 2.2 to 4 per inch, meaning it requires significantly more thickness to achieve the same insulating power as spray foam. This can reduce usable space in attics, basements, or walls, especially when meeting higher R-value requirements like R50.
- Rock Wool (Mineral Wool): Offers an R-value of 3.3 to 4 per inch, slightly better than fiberglass. While denser and more stable, rock wool also requires more depth than spray foam to achieve equivalent thermal performance, making it less space-efficient for walls or ceilings.
- Blown-In Cellulose: Provides an R-value of 2.7 per inch, comparable to fiberglass but lower than spray foam. Cellulose’s loose-fill nature makes it effective at filling irregular spaces, but it requires greater thickness to meet higher R-value requirements and can settle over time, reducing its effectiveness.
Cost: A Simple Breakdown
To provide a clear comparison, we’ve outlined the cost per square foot for each insulation type across three common applications: exterior walls (R24), attics (R31 for spray foam; R50 for blown-in insulation), and basements (R20).
These costs reflect current building code requirements, including the mandated use of rigid foam board for exterior walls, regardless of the insulation type used.
Exterior Walls (R24)
Under Ontario’s current building code, rigid foam board is required for all insulation types to meet R24 requirements, even though spray foam can achieve R24 on its own without additional materials. This regulation makes the cost of spray foam and fiberglass comparable in the short term. However, once the regulations are updated, spray foam may eliminate the need for rigid foam board, offering potential future cost savings.
- Spray Foam: $6.00/sqft (baseline)
- Rock Wool: $4.45/sqft (~26% cheaper than spray foam)
- Fiberglass: $3.60/sqft (~40% cheaper than spray foam)
Attics (R31 for Spray Foam; R60 for Blown-In Insulation)
The difference in required R-values for spray foam versus blown-in insulation significantly impacts cost and functionality. Spray foam is applied directly to the roof decking, achieving R31 with minimal thickness while sealing the entire space. This approach preserves attic usability for storage or even living areas.
In contrast, blown-in fiberglass and cellulose must meet an R50 requirement, requiring thicker layers that sit on the attic floor. This not only increases the amount of material needed but also renders the attic space unusable, as the insulation obstructs the floor and doesn’t seal air leaks effectively.
- Spray Foam (R31): $7.50/sqft
- Blown Fiberglass (R60): $4.50/sqft (~40% cheaper than spray foam)
- Blown Cellulose (R60): $3.50/sqft (~53% cheaper than spray foam)
Basements (R17)
Basements are traditionally damp environments, posing significant challenges for insulation. Both fiberglass and rock wool lose effectiveness when exposed to moisture, as they absorb water, leading to potential mold growth and degradation. Spray foam, on the other hand, acts as both an insulator and a superior moisture barrier, sealing the basement and protecting against dampness. This makes spray foam the clear choice for insulating basements effectively.
- Spray Foam (R17): $4.50/sqft
- Rock Wool (R14): $3.60/sqft (~20% cheaper than spray foam)
- Fiberglass (R14): $3.00/sqft (~33% cheaper than spray foam)
Why Rigid Foam Board Costs Matter
Although spray foam insulation can independently meet or exceed R24 requirements, Ontario’s building code has not yet adapted to this capability. As a result, rigid foam boards are still required in current designs, adding costs for all insulation types.
Once the code catches up to reflect the efficiency of spray foam, rigid foam boards may no longer be necessary when using spray foam, leading to potential savings in exterior wall construction.
Click here for more info on the price of spray foam insulation.
Air Sealing Capability
Effective air sealing is crucial for maintaining energy efficiency and preventing drafts:
- Spray Foam: Creates a complete air barrier, eliminating drafts and improving energy efficiency. Its high R-value in minimal thickness also helps maintain space efficiency, making it ideal for attics, basements, and exterior walls.
- Fiberglass: Poor air sealing; requires vapor barriers to minimize air leakage. Even though it’s marketed as DIY-friendly, achieving an airtight seal with fiberglass is not easy and can lead to moisture issues if not properly installed.
- Rock Wool: Better than fiberglass but still needs additional support for complete air sealing. Its thicker profile can limit interior space compared to spray foam.
- Blown-In Cellulose: Does not inherently seal air gaps and can settle over time, creating potential for air leakage. It’s best used in enclosed spaces like attics where settling has minimal impact.
Moisture Resistance
- Spray Foam: Impermeable to water; prevents mold and mildew growth.
- Fiberglass: Absorbs moisture, risking mold and performance degradation, especially if the vapor barrier is not perfectly sealed.
- Rock Wool: Water-resistant but not waterproof; can handle some moisture without significant impact.
- Blown-In Cellulose: Can absorb and hold moisture, leading to potential mold issues and reduced insulation effectiveness over time.
Fire Resistance
- Spray Foam: Doesn’t ignite easily and only requires a fire retardant coating when exposed.
- Fiberglass: Non-combustible but can melt at high temperatures.
- Rock Wool: Naturally fire-resistant; can withstand high temperatures without burning.
- Blown-In Cellulose: Treated with fire retardants, but if exposed to water and not properly maintained, its fire resistance can degrade over time.
Soundproofing
For homeowners looking to reduce noise between rooms or from outside, soundproofing is a key consideration:
- Spray Foam: Provides some soundproofing due to its density, but it’s not as effective as other materials specifically designed for this purpose.
- Fiberglass: Offers moderate soundproofing, especially when used in interior walls or between floors. Its lower density compared to rock wool means less sound absorption.
- Rock Wool: The best option for soundproofing due to its dense, fibrous structure. Ideal for use in media rooms, between floors, or in shared walls for superior noise reduction.
- Blown-In Cellulose: Provides good soundproofing, especially in attics and enclosed spaces. Its loose-fill nature helps to dampen sound transmission more effectively than fiberglass.
Durability and Longevity
- Spray Foam: Extremely durable and long-lasting. Once installed, it doesn’t settle or degrade, maintaining its R-value and air-sealing properties for decades.
- Fiberglass: Prone to settling and compression over time, which can reduce its effectiveness. It can also degrade if exposed to moisture or pests.
- Rock Wool: More stable than fiberglass and less prone to settling. It retains its shape and effectiveness longer but may compress slightly over many years.
- Blown-In Cellulose: Tends to settle over time, reducing its effectiveness and R-value. It may need to be topped up periodically to maintain performance.
Environmental Impact
- Spray Foam: Made from petroleum-based products, it has a higher environmental impact during manufacturing. However, it can contribute to long-term energy savings, reducing the home’s overall carbon footprint.
- Fiberglass: Often made from recycled glass, making it a more eco-friendly option. However, the manufacturing process can be energy-intensive, and it’s less efficient at reducing energy loss compared to spray foam.
- Rock Wool: Produced from natural and recycled materials, it has a lower environmental impact. It’s also fully recyclable, making it a good choice for those prioritizing sustainability.
- Blown-In Cellulose: Made from recycled paper products, it’s one of the most environmentally friendly insulation options available. However, its fire retardant treatment and potential settling over time are considerations.
Installation Method
- Spray Foam: Requires professional installation by certified professionals due to the technical nature of the application and safety considerations. This ensures proper application and maximizes insulation performance.
- Fiberglass: Available in DIY-friendly batts and blown-in forms. While installation is relatively straightforward, achieving a proper seal with vapor barriers is challenging and essential to prevent future issues.
- Rock Wool: More challenging to install than fiberglass, especially in tight spaces. It’s often handled by professionals due to its dense and rigid structure.
- Blown-In Cellulose: Typically requires professional installation, especially for enclosed spaces and wall cavities. It’s less DIY-friendly due to the equipment needed and the risk of over-compression and settling.
Comparison Table
| Factor | Spray Foam | Fiberglass | Rock Wool | Blown-In Cellulose |
| R-Value per Inch | 6.5 – 7 | 2.2 – 3.8 | 3.3 – 4.2 | 3.2 – 3.8 |
| Cost (Exterior Walls R24) | $6.00/sqft (baseline) | $3.60/sqft (~40% cheaper) | $4.45/sqft (~26% cheaper) | N/A |
| Cost (Attics R31) | $7.50/sqft (baseline) | $4.50/sqft (~40% cheaper) | N/A | $3.50/sqft (~53% cheaper) |
| Cost (Basements R17) | $4.50/sqft (baseline) | $3.00/sqft (~33% cheaper) | $3.60/sqft (~20% cheaper) | N/A |
| Air Sealing | Excellent | Poor | Moderate | Poor |
| Moisture Resistance | Impermeable | Absorbs Moisture | Water-resistant | Can absorb moisture |
| Fire Resistance | Does not ignite | Non-combustible, can melt | Highly fire-resistant | Treated, but can degrade |
| Soundproofing | Moderate | Moderate | Excellent | Good |
| Durability | Does not settle | Can settle | Holds shape | Can settle |
| Environmental Impact | Higher impact, long-term savings | Recycled glass, lower efficiency | Natural, recyclable | Recycled paper, sustainable |
| Installation | Professional only | DIY-friendly but challenging to seal | Professional preferred | Professional preferred |
| Best Use Cases | Attics, basements, walls, crawl spaces | Attics, walls, ceilings | Soundproofing, fire-prone areas | Attics, enclosed spaces |
Whole House Seal: What It Means and Why It Matters
A whole house seal is one of the key benefits of using closed-cell spray foam insulation. This involves creating a continuous barrier around the entire home, from the basement slab to the exterior walls and up to the roof deck. This comprehensive seal prevents air leakage, which is one of the main causes of energy loss in homes. Here’s how it works:
- Eliminates Air Gaps: Traditional insulation types, like fiberglass, can leave small gaps and cracks around electrical outlets, windows, and doors. These gaps let conditioned air escape and outside air in, making your HVAC system work harder to maintain a consistent indoor temperature.
- Prevents the Stacking Effect: This is when warm air rises and escapes through the roof, pulling in cold air from the lower parts of the house. A whole house seal stops this cycle, keeping your home more comfortable and reducing energy costs.
- Structural Support: Closed-cell spray foam also adds rigidity to the structure, reinforcing walls and roof decks against weather-related stress.
Real-Life Scenarios and Use Cases
Attic Insulation
- Spray Foam: Its high R-value in minimal thickness allows you to insulate the roof deck without taking up much space, preserving attic height for storage or living areas.
- Fiberglass: Requires more depth to achieve similar R-values, which can reduce usable space.
- Rock Wool: Effective for soundproofing but takes up more space, making it less suitable for maximizing attic utility.
- Blown-In Cellulose: Provides good insulation coverage in attics but can settle over time, reducing its effectiveness.
Basement Insulation
- Spray Foam: Efficiently insulates with less thickness, maintaining maximum floor area and ceiling height, ideal for finished basements.
- Fiberglass: Needs thicker layers, which can encroach on interior space and height.
- Rock Wool: Similar to fiberglass in terms of space requirements but with better soundproofing.
- Blown-In Cellulose: Not ideal for basements due to potential moisture absorption, which can lead to mold issues.
Exterior Wall Insulation
- Spray Foam: Achieves required R-values within standard wall cavities, eliminating the need for exterior rigid foam. This simplifies construction and maintains the exterior profile of the home.
- Fiberglass: May need additional exterior insulation to meet code requirements, adding bulk and complexity.
- Rock Wool: Provides good insulation but usually requires more depth, making it less efficient for tight wall cavities.
- Blown-In Cellulose: Works well in enclosed wall cavities, but may require periodic maintenance due to settling.
Additional Uses of Spray Foam
Spray foam is incredibly versatile, extending beyond traditional home insulation:
- Rural Applications: Insulates buried water pipes, preventing them from freezing in harsh climates. For every inch of spray foam applied, it mimics the insulation of a foot of soil, making it ideal for shallow-buried pipes in rural settings.
- Cottage Crawl Spaces: Used to insulate the undersides of cottages raised above the ground, preventing cold air and moisture from entering the living space, and keeping floors warmer in winter.
- Commercial and Industrial Insulation: Commonly used in warehouses, storage tanks, and cold storage facilities due to its superior insulating and moisture-resistant qualities.
- Soundproofing: Effective in music studios and commercial spaces.
- Waterproofing: Applied on foundations, roofs, and even boats to prevent water infiltration.
While spray foam serves multiple purposes, traditional insulations like fiberglass and rock wool are primarily limited to thermal and sound insulation within buildings.
FAQs and Misconceptions
- Q: How much will spray foam save me in energy costs?
- A: It can reduce energy bills by 20-30% annually, depending on factors like climate, home size, and HVAC efficiency. For more information about the energy savings of spray foam read Maximizing Energy Efficiency: How Spray Foam Insulation Lowers Your Bills by 30%
- Q: Is it worth the extra cost for a whole house seal?
- A: Yes, for most homeowners. The whole house seal prevents energy loss through air leaks, improving comfort and reducing long-term costs.
- Q: Does fiberglass pose health risks?
- A: Fiberglass can irritate the skin and lungs during installation. Proper protective gear is essential. Once installed and sealed, the risks are minimal.
- Q: Is rock wool really fireproof?
- A: Rock wool is highly fire-resistant and won’t burn, making it an excellent choice for fire-prone areas or between floors in multi-family homes.
Final Thoughts
Choosing the right insulation depends on your specific needs and priorities. Closed-cell spray foam offers the best air sealing, moisture resistance, and space efficiency, making it ideal for attics, basements, and exterior walls. Fiberglass is a cost-effective option for DIY projects in attics and walls but requires careful installation to avoid moisture issues. Rock wool provides superior soundproofing and fire resistance, making it perfect for interior walls and multi-family homes. Blown-in cellulose is an eco-friendly option with good thermal properties but may settle over time, reducing its effectiveness.
No matter what you choose, ensuring proper installation and considering your home’s unique requirements will make all the difference.
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