Spray Foam vs Fiberglass Insulation: Which Cuts Energy Bills More? [2025]
The battle between spray foam vs fiberglass insulation comes down to cold, hard numbers. Spray foam delivers impressive R-values of 5 to 7 per inch, while fiberglass trails behind at just 2.9 to 3.8 per inch. This stark difference has homeowners scratching their heads about which option truly makes sense for their homes.
Sure, spray foam's superior insulating power doesn't come cheap. You'll pay $1.50 to $3.00 per square foot compared to fiberglass at a mere $0.10 to $0.50. But here's what many homeowners miss: spray foam creates an airtight seal that fiberglass simply can't match, plus it lasts 30-50 years without degrading. Meanwhile, fiberglass tends to sag and settle, gradually losing effectiveness over time.
So what should you consider when choosing between these options? The true cost-benefit equation goes beyond initial price tags. This guide breaks down how each insulation type impacts your monthly energy bills, examines real-world performance differences, walks through installation considerations, and calculates long-term value to determine which option puts more money back in your pocket over time.
R-Value and Heat Retention: How Each Insulation Performs
R-value measures how well insulation resists heat flow. The higher the R-value, the better the material performs at stopping heat transfer. This seemingly simple number makes a world of difference for homeowners trying to keep energy bills in check, especially in harsh Canadian winters.
Open-cell vs closed-cell spray foam: R-value per inch
Closed-cell spray foam dominates the insulation market with impressive R-values between 6 and 7 per inch. Why does this matter? This dense material creates a powerful barrier against heat loss, perfect for spaces where you need maximum insulation without adding bulk. Open-cell spray foam, while less robust, still delivers respectable R-values of 3.5 to 3.9 per inch.
The performance difference comes from their structure - closed-cell foam packs a denser composition that simply takes longer for heat to move through. What many homeowners don't realize is that when temperatures plummet below freezing (around 20°F), the gap between spray foam and fiberglass becomes even more dramatic.
Fiberglass batts and blown-in: R-value range and limitations
Fiberglass insulation falls significantly short of spray foam's performance. Batts typically achieve just R-2.2 per inch, while blown-in versions perform slightly better at R-2.2 to R-3.5 per inch. Most fiberglass products come in batts and rolls ranging from R-8 to R-49 for complete installations.
But these base numbers don't tell the whole story. Fiberglass comes with several performance issues:
R-value decreases as the material ages
During extreme cold (below 20°F), fiberglass can lose up to 50% of its effective R-value
Blown-in varieties settle over time, reducing thickness and insulating power
This settling often requires "topping up" to maintain protection
The numbers on paper only tell half the story. Spray foam creates an air seal that blocks convective heat transfer, while fiberglass lets air move through, dramatically affecting real-world performance. This means the actual difference between spray foam and fiberglass can be even more significant than the R-values suggest - a crucial factor for homeowners making this important decision.
Air Sealing and Moisture Control: Impact on Energy Bills
R-value gets all the attention, but air sealing and moisture control might actually be the hidden champions of energy efficiency. These factors often matter more than insulation thickness when it comes to your monthly energy bills.
Spray foam's airtight seal and humidity control
Spray foam insulation creates an exceptional barrier by expanding to fill every crack and gap throughout your walls, attics, and crawl spaces. This sealing action isn't just good—it reduces air permeability by 24 times compared to average rates. Let that sink in: air leakage causes approximately 40% of a home's energy loss. By creating a complete air seal, spray foam can slash heating and cooling costs by up to 50%.
The magic of spray foam lies in its multi-tasking abilities. It's the only single-step product that functions as both thermal insulation and an air barrier. Beyond that, it creates a protective moisture barrier that guards against water infiltration in vulnerable areas like attics and crawl spaces, remaining water-resistant even during flooding.
Closed-cell spray foam delivers superior water resistance, making it perfect for spaces with moisture concerns. Open-cell varieties, while less moisture-resistant, still provide effective humidity control and solid air sealing.
Fiberglass insulation and air leakage in older homes
The biggest problem with fiberglass? It simply cannot stop air leakage. Fiberglass batts and rolls fail to create an air seal, allowing outside air to freely move through gaps and cracks. This weakness becomes particularly problematic in older Canadian homes, which typically suffer from more significant air leakage than newer construction.
Want to spot air leakage with fiberglass? Look for dirty insulation—it essentially acts as a giant air filter, collecting dust instead of stopping airflow. Worse still, fiberglass absorbs moisture over time, creating potential mold and mildew problems while dramatically reducing its insulating effectiveness.
Fixing these issues with fiberglass requires extra steps and materials:
Since fiberglass batts don't provide an air seal, you must add a separate air barrier
Because fiberglass can't function as a vapor barrier, you need to install a separate moisture barrier
These additional requirements increase both installation complexity and total cost
The good news? Properly sealing air leaks and installing quality insulation can deliver up to 10% savings on your annual energy bills—critical information for homeowners trying to make the right choice between these insulation options.
Cost vs Savings: Which Insulation Pays Off Faster?
The dollars and cents of insulation choices tell a fascinating story when you look beyond the price tag. The decision between spray foam and fiberglass isn't just about today's costs—it shapes your home's energy budget for decades.
Spray foam vs fiberglass insulation cost in $CAD
Spray foam comes with a significantly higher upfront investment. Expect to pay around CAD 4.18 per square foot for 3 inches of thickness, while fiberglass costs only about CAD 0.56 per square foot. Breaking it down further:
Open-cell spray foam: CAD 0.61 to CAD 0.91 per board foot
Closed-cell spray foam: CAD 1.39 to CAD 2.09 per board foot
Fiberglass batt insulation: CAD 0.42 to CAD 2.09 per square foot
Different areas of your home will command different pricing, with attic installations typically running between CAD 2,090.04 and CAD 8,360.16 total.
Energy bill reduction over 5, 10, and 20 years
Here's where the story gets interesting. The premium you pay for spray foam starts paying you back immediately through energy savings. Homeowners who switch to spray foam insulation typically cut their heating and cooling bills by 30-35%. What does this mean in real money? For a home with monthly energy costs of CAD 418.01, you're looking at savings up to CAD 125.40 every month—adding up to CAD 1,393.36 annually.
Studies show spray foam typically pays for itself within 5-6 years. After crossing this threshold, everything else is pure savings in your pocket. And as traditional insulation materials lose effectiveness while spray foam maintains its performance, the financial advantage grows even more dramatic over time.
Maintenance and degradation: long-term performance
The longevity factor dramatically shifts the cost equation. Spray foam insulation lasts an incredible 80 to 100 years when properly installed. Throughout this entire period, it needs zero maintenance and doesn't deteriorate, sag, or settle.
Fiberglass tells a different story. While it could theoretically last up to 100 years in perfect conditions, its effectiveness plummets when exposed to even small amounts of moisture. Most fiberglass installations need replacement or significant reinforcement after just 20 to 30 years—an extra future cost that spray foam owners simply don't face.
Installation and Lifespan: What Affects Efficiency Over Time
Even the best insulation materials fail when improperly installed. Your insulation's long-term performance depends heavily on installation quality and material durability—factors that directly impact both your comfort and monthly bills for decades to come.
Professional vs DIY installation: energy loss risks
Think twice before grabbing that DIY insulation kit at the hardware store. Professional installation offers major advantages for both materials. With spray foam, expert application isn't just recommended—it's practically essential. The material dries incredibly fast once installation begins, and mistakes happen quickly. Without proper technique, open-cell foam can fold over itself, creating hidden air pockets that severely compromise performance. These undetected gaps lead to moisture buildup and gradual efficiency loss.
Fiberglass comes with its own installation headaches. Industry experts consistently find that DIY fiberglass installation creates gaps or compression points that dramatically reduce insulating effectiveness. Proper installation isn't just about stuffing material between studs—it requires careful attention to ventilation, moisture management, and maintaining the right thickness. Homeowners often overestimate their installation skills, and these mistakes can cancel out much of the insulation's value.
Safety concerns make the professional route even more appealing. Fiberglass particles can cause serious respiratory problems without proper protective gear, while spray foam installation releases toxic fumes requiring respirators and protective suits.
Durability and sagging: how it affects insulation value
Insulation materials age very differently. Fiberglass insulation, especially when not perfectly installed, tends to settle and sag over time, creating gaps that significantly reduce its R-value. This settling often means replacement after just 15-20 years, even though the material could theoretically last longer under perfect conditions.
Spray foam tells a completely different story. Properly installed foam maintains its shape without sagging or settling, potentially lasting 80-100 years. It's not perfect though—spray foam can occasionally contract in areas with extreme temperature swings, which does reduce its insulating effectiveness.
Moisture exposure creates the most dramatic performance difference between these materials. When fiberglass gets wet, the fibers clump together and lose effectiveness—often requiring complete replacement. Closed-cell spray foam, being essentially watertight, maintains its performance even in humid environments, making it especially valuable in wet climates or problem areas like basements.
Age affects all insulation materials to some degree, but these durability differences dramatically impact the true lifetime value of your insulation investment.
Making the Final Choice: Long-Term Value vs Initial Investment
The spray foam vs fiberglass debate boils down to a classic question: pay now or pay later?
Spray foam clearly emerges as the superior option for Canadian homeowners focused on long-term energy savings and comfort. Yes, the initial investment hits harder at CAD 4.18 per square foot compared to fiberglass at just CAD 0.56, but the numbers beyond the price tag tell the real story.
Spray foam's R-value advantage (5-7 per inch versus fiberglass at 2.9-3.8) is just the beginning. The game-changer is spray foam's airtight seal that addresses the 40% energy loss through air leakage that fiberglass simply cannot stop. This translates to energy bill reductions of 30-35%, meaning most homeowners recover their investment within 5-6 years. After that? It's all savings.
Durability delivers another knockout punch for spray foam. The material keeps performing for 80-100 years without sagging or settling, while fiberglass typically needs replacement or significant reinforcement after just 20-30 years. This difference becomes critical in Canada's harsh climate, where temperature extremes can devastate insulation performance.
So which should you choose? It depends on your situation:
Planning to stay in your home long-term? Spray foam's superior performance and longevity make it the smarter investment.
Working with tight budget constraints or short-term housing plans? Fiberglass might make more immediate sense—but factor in those higher monthly energy bills and potential replacement costs.
The smartest move for any Canadian homeowner serious about maximizing energy efficiency? Consult with qualified insulation professionals who can provide personalized recommendations based on your specific climate conditions and building characteristics. The right choice today shapes your comfort and energy bills for decades to come.
