What Is The R-Value of Spray Foam Insulation ?
When upgrading your home insulation, understanding R-value is the first step toward better energy efficiency and comfort. To determine the ideal R-value for your insulation needs, factors such as your location's climate and the specific areas you plan to insulate come into play. Geographic zone, as defined in the USA's climate chart, plays a pivotal role in selecting the appropriate R-value for your insulation project, ensuring optimal energy efficiency and comfort in your home. This guide explains what R-value means, how much you need based on your climate zone.
What is R-Value?
R-value measures how effectively an insulation material resists heat flow — the higher the R-value, the greater the insulation performance.
Simply put, R-value tells you how well your insulation keeps heat inside during winter and outside during summer.
For example:
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An insulation with an R-value of 6 per inch performs twice as efficiently as one with R-3 per inch.
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A properly insulated home can reduce heating and cooling energy use by 25–40%.
How Much R-Value Do You Need?
The required R-value depends mainly on your U.S. climate zone and which part of the home you’re insulating.
Colder regions (Zones 5–8) require higher R-values to prevent heat loss, while warmer zones (1–3) need moderate levels for cooling efficiency.
USA Insulation R-Value Recommendations (2025)
| Climate Zone | Attic | 2x4 Wall | 2x6 Wall | Floor | Crawl Space | Basement Wall |
|---|---|---|---|---|---|---|
| Zone 1 (FL, HI) | R-30–R-38 | R-13–R-15 | R-19–R-21 | R-13 | R-13 | R-11 |
| Zone 2 (TX, LA) | R-38 | R-13–R-15 | R-19–R-21 | R-19–R-25 | R-13–R-19 | R-11 |
| Zone 3 (SC, GA) | R-38 | R-13–R-15 | R-19–R-21 | R-19–R-25 | R-19–R-25 | R-11 |
| Zone 4 (KS, TN, VA) | R-49 | R-13–R-15 | R-19–R-21 | R-25–R-30 | R-25 | R-11–R-15 |
| Zone 5 (NY, IL, CO) | R-49 | R-13–R-15 | R-19–R-21 | R-25–R-30 | R-25 | R-15–R-20 |
| Zone 6–8 (MN, ND, ME) | R-49–R-60 | R-15–R-21 | R-21–R-25 | R-30 | R-25 | R-20–R-25 |
(Data based on 2025 IECC recommendations.)
Tip: You don’t always need the highest R-value. The goal is to match your insulation level to your local zone for the best energy savings-to-cost ratio.
What Is The R-Value of Spray Foam Insulation?
There are two main types of spray foam — open-cell and closed-cell — each with different R-values and uses.
Closed-Cell Spray Foam R-Value
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R-Value: ~R-6.0 to R-7.2 per inch
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Structure: Dense and rigid with sealed cells
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Best for: Basements, crawl spaces, attics, and exterior walls
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Advantages: Highest insulation per inch, vapor-barrier properties, and structural reinforcement
Kraken Fast Coat Closed-Cell Spray Foam offers an R-value of 5.6–6.5 per inch, expanding up to 60× its volume for a tight, durable air seal.
Open-Cell Spray Foam R-Value
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R-Value: ~R-3.5 to R-3.8 per inch
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Structure: Soft and flexible with interconnected air pockets
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Best for: Interior walls and soundproofing applications
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Advantages: Lightweight, expands more per ounce, fills irregular spaces easily
How Insulation Works: The Science Behind R-Value
The fundamental goal of insulation is to prevent or at least slow down the transfer of the heat from the heated places to the unheated places at your home or from inside your house to outside. Insulation works in this way by reducing conduction, convection, and radiation.
1. Conduction
Heat moves through materials in contact — like warmth traveling through a metal spoon.
Spray foam slows conduction by creating millions of micro-bubbles that trap air.
2. Convection
Warm air rises and cold air sinks, creating circulation.
Proper insulation stops these air loops, cutting energy waste by 20–30%.
3. Radiation
Radiant heat moves as electromagnetic waves — like sunlight through a window.
High-R-value insulation helps reflect or absorb this radiant heat before it enters your living space.
Together, these three resistances explain why a well-insulated home may require up to 70% less energy to maintain a stable indoor temperature.
Closed-Cell vs Open-Cell: Which R-Value Is Right for You?
| Feature | Closed-Cell | Open-Cell |
|---|---|---|
| R-Value (per inch) | 6.0 – 7.2 | 3.5 – 3.8 |
| Density | High (rigid) | Low (soft) |
| Moisture Resistance | Excellent | Moderate |
| Soundproofing | Moderate | Excellent |
| Vapor Barrier | Yes | No |
| Cost (approx.) | $1.70–$3.00 / sq. ft | $0.90–$1.40 / sq. ft |
| Best For | Exterior walls, basements, attics | Interior walls, ceilings, studios |
Why Choose Kraken Fast Coat for Optimal R-Value Performance
Kraken Fast Coat Spray Foam Kit delivers professional-grade results with a balanced R-value of ≈5.6 per inch and ultra-easy DIY application.
Each kit covers up to 240 sq ft at 1-inch thickness, allowing homeowners to achieve proper insulation levels without hiring a contractor.
Highlights:
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Seals air leaks and moisture gaps
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Expands 60× for maximum coverage
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Reduces HVAC load by up to 35%
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Low-VOC and 100% HFC-free
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Ideal for attics, crawl spaces, van conversions, and basements
Learn more about Kraken Fast Coat Spray Foam Insulation
FAQs About Spray Foam R-Value
What does R-value really mean?
R-value measures how well insulation resists heat flow — higher numbers mean better energy efficiency.
What is the R-value of closed-cell spray foam?
Closed-cell foam averages R-6 to R-7 per inch, the highest among insulation materials.
What is the R-value of open-cell spray foam?
Open-cell foam averages R-3.5 per inch, ideal for interior applications where sound control matters.
How much R-value do I need in my zone?
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Zones 1–3: R-30–R-38 for attics
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Zones 4–5: R-49 for attics, R-19–R-21 for walls
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Zones 6–8: R-49–R-60 for attics, R-25 for walls and basements
Can I combine open-cell and closed-cell foam?
Yes — hybrid systems are common, using closed-cell for moisture areas and open-cell for soundproofing.
Is a higher R-value always better?
Not necessarily; too high an R-value can be overkill in warm climates. Match it to your IECC zone for best cost-efficiency.
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Author : Krakenbond Team
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Sprayed my mudroom and did very well it is a lot warmer in there now. Easy application and cleanup. 10x13.
Sprayed in two coats as in one heavy coat, it fell down. Went to two and worked quite well. Didn't realize the two red plastic pieces were nozzles until I was 3/4 done. Worked much better when using them. Was told by three commercial insulation installers this project could not be done but with a little extra preparation was able to do it myself for a fraction of the cost! Would not have needed the extension I purchased as regular nozzle sprayed further than I thought it would.
My order shipped quickly, and product goes on nicely. Even with the cost of labor for someone I hired to help with the application, the cost was a small fraction of what I was quoted by an insulation service.
Getting ready to use it this week thanks again for the support !!
Worked great. Ordering more. INSANE quick shipping. My dad was very pleased.
Great product. We use approximately two cases a week
FastCoat Insulation Spray Foam, Closed Cell Expanding Foam | Class A Fire Rated
I was back and forth about using foam board or you product for my crawl space. I was impressed at the quality of the kit and the ease of the application, there is a little bit of a learning curve on the first can with the gun, but that is to be expected for the first time use.
This kit is awsome it contains everything needed to do small to medeam size jobs with ease i would buy again
I always use Kraken products
Product is amazing very satisfied with customer service and the ease of use spray foaming my building.
I like it & would be interested in 4 more cases if i could still get them for this price
Shipping was super fast , less than 24 hrs from order to my door !! Product is very easy to use , but definitely get more than you think you will need. Slight learning curve. Over all %100 satisfied.
As advertised
Awesome product. Worked as described
Really interesting post!
How much will I need for bldg 30×30×12’high
I need to do a crawl space cement wall 4ft high around 40ft long
40ft.long. 8ft. Tall. Wall. How much$$
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