Closed cell and open cell spray foam insulation are both used in Chicagoland homes, but they have different performance characteristics that make them suited for different areas of your house.
Closed cell spray foam has the highest R-value. It’s rigid, inflexible, and moisture-resistant. This makes it best for attics, crawl spaces, basements, exterior walls, and anywhere moisture or vapor control is required. Open cell spray foam has a lower R-value and is more affordable. It’s soft and flexible, with a high expansion rate, but it’s not moisture-resistant. This makes it best for interior walls, tough-to-reach places, and anywhere moisture control isn’t needed.
Difference Between Open and Closed Cell Spray Foam
Besides their physical differences, closed cell and open cell spray foam have different performance properties. Many people ask, “Which is better, open or closed cell?” It all comes down to what the insulation is being used for. One isn’t universally better than the other.
Open Cell vs Closed Cell R-Value
R-value, or the insulation’s thermal resistance, is the main performance difference between the two types of spray foam. Closed cell offers a higher R-value, so it prevents more heat transfer per square inch.
- Closed Cell R-Value (Per Square Inch): 7.0
- Open Cell R-Value (Per Square Inch): 3.8
In practice, open cell can sometimes insulate a home just as well as closed cell, but it depends on how much space is available. Closed cell usually expands to 1.5’’, whereas open cell usually expands to 3.5’’. In spaces like a wide-open attic, open cell can fully expand to 3.5” and provide more R-value than 1.5” of closed cell (3.8 x 3.5” vs. 7.0 x 1.5”). While you can layer closed cell once it settles, open cell is usually the better option for these spaces.
In confined spaces like walls, however, there may not be enough space for open-cell spray foam to fully expand. Therefore, closed cell spray foam is the better insulation option because it offers a higher R-value.
Moisture Resistance and Air Blocking
One of the main benefits of closed cell spray foam is that it’s water impermeable, meaning moisture and vapor cannot pass through it. This is important for parts of the house that are prone to humidity and moisture buildup, such as the attic and basement. Closed cell spray foam also blocks airflow, making it good for air sealing.
Open cell is permeable, so it doesn’t block moisture from entering spaces like the attic. Therefore, it can’t prevent humidity or condensation from building up. However, it can provide air sealing when sprayed at the recommended thickness of three inches.
Sound Deadening
Since open cell spray foam expands so much (about three and a half inches per pass), it also provides sound-deadening properties. Many people use it within their home to quiet noise transfer from one room to another, and to block out noise from the outdoors.
Closed cell spray foam doesn’t provide the same level of sound deadening because it can only stop noise coming from air gaps. However, it can be used within walls to improve structural integrity.
Open Cell vs Closed Cell Spray Foam Costs
In general, spray foam insulation costs between $2 and $10 per square foot, depending on a variety of factors like the size and accessibility of the area, whether insulation removal or mold remediation is needed, and most importantly, what type of spray foam you use.
Closed cell spray foam usually costs two to three times more than open cell spray foam.
When to Use Closed Cell Spray Foam
Closed cell spray foam is ideal for Chicagoland homes. Its high R-value helps keep the home warm in the winter, keeping utility bills low. Its moisture-resistant and air-sealing properties are an important asset during humid summers, because it keeps muggy air from entering your home, which would then condense and turn into mold.
Some of the most common areas it’s used include:
- Attics and roof decks
- Crawl spaces and basements
- Exterior walls during new construction
- Areas requiring moisture or vapor control
When to Use Open Cell Spray Foam
Open cell spray foam should not be used in any area of the home that’s prone to moisture. This means it’s generally not a good candidate for weatherization, because inadequate insulation is most commonly found in the basement, crawl space, and attic, right where moisture loves to collect. However, it’s still useful for:
- Interior walls (for soundproofing)
- Hard-to-reach areas (the flexibility helps during installation)
- Spaces where moisture control is not critical
Comparison Table: Closed Cell vs Open Cell Spray Foam
|
Closed Cell Spray Foam |
Open Cell Spray Foam |
|
|
R-Value |
~6.5 |
~3.6 |
|
Moisture-Resistance |
Very moisture resistant. Impermeable and can serve as a vapor barrier. |
Not moisture resistant. Permeable, so water and humid air can pass through. |
|
Soundproofing |
Minor noise reduction by sealing air gaps. |
Excellent soundproofing, especially between walls. |
|
Expansion |
1″–1.5″ per pass. |
3″–3.5″ per pass. |
|
Cost |
2–3x the cost of open cell |
2–3x cheaper than closed cell |
|
Where to Use |
Attics, basements, crawl spaces, exterior walls. |
Interior walls. |
ARC Insulation’s Expertise
Since 1993, ARC Insulation has been providing high-quality insulation services to Chicagoland and Naperville. We are BPI-certified professionals who take a performance-based approach to our work. Instead of being satisfied with installing to code, we test after our installation to make sure your new insulation provides maximum performance.
With over 30,000 homes served, our company can help you decide whether open cell or closed cell spray foam is best so that your home can be more energy efficient, comfortable, and moisture-free.
