When it comes to insulating your home, two of the most popular options are spray foam insulation and fiberglass insulation. Both have their advantages and disadvantages in terms of effectiveness, cost, and ease of installation. Many homeowners struggle to decide which is the better choice for their needs and budget.
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The Basics of Spray Foam and Fiberglass Insulation
Spray foam insulation is typically made from polyurethane or polyicynene foam. It is sprayed into place as a liquid and then expands to fill cracks and crevices, creating a seamless air barrier. Once cured, it is rigid and adds structural stability. Spray foam provides robust insulation, with an R-value around R-6 to R-7 per inch. It is an effective method for insulating irregularly shaped areas and reducing air leaks.
Fiberglass insulation is made from extremely fine fibers of glass. It comes in rolls or batts that are installed between wall studs, floor joists, attic rafters, etc. Fiberglass is not as densely packed as spray foam, so it rates at R-3 to R-4 per inch. The insulation does not expand to fill gaps, so it must be cut to fit perfectly or combined with caulk or spray foam for the best air sealing.
Upfront Cost Comparison
When comparing the upfront costs of spray foam vs. fiberglass insulation, spray foam is almost always more expensive:
- Fiberglass insulation costs $0.75-$1 per square foot on average
- Spray foam insulation costs $3-$7 per square foot installed
Spray foam insulation costs 400-900% more than fiberglass initially. However, it’s important to consider the labor costs for installation as well.
Fiberglass Insulation Costs
For fiberglass batt installation, you’ll need to account for:
- Insulation materials – $0.75-$1 per square foot
- Labor – $1-$2 per square foot
This puts the total installed cost of fiberglass around $1.75-$3 per square foot. Insulation for a typical 2,000 sq.ft. home would cost $3,500-$6,000.
Spray Foam Insulation Costs
For spray foam, the costs include:
- Materials – $3-$7 per square foot
- Labor – included in material cost
- Equipment rental fees – $500-$1000 per day
Expect to pay $4,000-$14,000 to have spray foam professionally installed in a 2,000 sq.ft. home. The exact cost depends on the type of foam used and the thickness applied.
Energy Savings
While spray foam’s higher initial cost may be hard to swallow, it can pay off over time through energy savings. Let’s compare the energy efficiency of these two insulation types:
Fiberglass Insulation Efficiency
The R-value of fiberglass ranges from R-3 to R-4 per inch. To achieve an insulation value that meets the current building code minimum of R-13 for 2×4 framed walls, you would need:
- 3.5 inches of R-13 batt insulation
- Or 5.5 inches of R-19 batt insulation
In real-world conditions, fiberglass may fall short of its rated R-value due to gaps, compressed batts, and air leaks. Proper installation is key to achieving expected energy efficiency.
Spray Foam Insulation Efficiency
With an insulation value of R-6 to R-7 per inch, spray foam outperforms fiberglass. To meet code minimums, you would only need:
- 2 inches of closed-cell spray foam
- Or 3 inches of open-cell spray foam
Because it expands and seals, spray foam is more consistent in achieving its rated R-value. It minimizes energy loss from air leaks. Most types also act as a vapor barrier, further preventing moisture issues.
Lifespan
When installed correctly in the proper setting, fiberglass and spray foam insulation should both last a very long time. Some key durability differences to note:
- Fiberglass insulation is susceptible to compression and settling over time. This can reduce R-value and create gaps.
- Moisture can encourage mold growth in fiberglass and impact insulation performance.
- Rodents and insects can nest in fiberglass insulation.
- Spray foam does not compress or settle over time.
- Closed-cell spray foam resists moisture and pests.
- Spray foam adds rigidity to improve framed wall strength.
Overall, spray foam maintains its insulation value better over decades of use. But fiberglass also remains effective when correctly installed in dry areas.
Other Factors to Consider
Here are some other factors that may sway your decision between fiberglass and spray foam insulation:
Installation Considerations
- Fiberglass is easier for DIY installation. Spray foam requires professional equipment and training.
- Spray foam is better for insulating irregular layouts and curved walls.
- Spray foam enables less invasive exterior insulation for renovations.
Vapor Permeability
- Fiberglass allows vapor diffusion for breathable homes.
- Closed-cell spray foam acts as a vapor barrier.
Fire Safety
- Fiberglass is naturally fire-resistant.
- Some spray foams use flammable installation materials.
Indoor Air Quality
- Fiberglass contains formaldehyde, which may affect air quality.
- Closed-cell spray foam prevents off-gassing of chemicals.
Consider how these factors apply to your specific home and climate when selecting insulation.
Cost Comparison Table
Here is a table summarizing the costs of fiberglass vs. spray foam insulation:
| Insulation Type | Cost per sq.ft. (Material + Labor) | Total Cost for 2,000 sq.ft. Home |
|---|---|---|
| Fiberglass Batt | $1.75-$3 | $3,500-$6,000 |
| Spray Foam | $4-$14 | $8,000-$28,000 |
Lifespan Comparison Table
Here is a table comparing the lifespan and durability differences between fiberglass and spray foam:
| Insulation Type | Lifespan | Durability Factors |
|---|---|---|
| Fiberglass | 20-50 years |
|
| Spray Foam | >50 years |
|
The Bottom Line
When comparing the costs of fiberglass vs. spray foam insulation, there is no clear “winner” – it depends on your specific needs, budget, and goals. Key takeaways include:
- Spray foam has a much higher initial cost, but offers stronger performance per inch.
- Fiberglass is more DIY-friendly and economical for typical stud wall insulation.
- Spray foam is preferred for irregularly shaped areas, exterior insulation, and minimizing air leaks.
- Both insulation types can be durable with proper installation. Spray foam may maintain performance better long-term.
- Consider vapor permeability, fire safety, and indoor air quality based on your climate and project scope.
Consult with insulation professionals to determine whether the added value of spray foam justifies the higher price tag for your next insulation project.