Closed Cell vs Open Cell: Which One is Best for Me?

Which Type of Spray Foam Should You Use?

Ask ten contractors which spray foam to use and you'll get ten different answers. One insists closed cell is king, another swears by open cell. The truth is that neither is universally better. The right choice comes down to the specific application, the goals you're trying to reach, and your budget. In this guide we'll walk through the real differences between open cell and closed cell spray foam so you can choose with confidence.

What's the Difference Between Open Cell and Closed Cell Spray Foam?

Cell Structure

Spray foam is called open cell or closed cell because of the structure of the material itself.

Open cell foam leaves a little room inside each cell, like a tiny air bubble, which makes the cured foam softer and more flexible. Some open cell foams are hydrophobic, meaning they retain only a small fraction of any water they contact and keep their shape, cell structure, and insulating properties as they dry naturally. Other open cell products can hold far more water, so it pays to ask exactly which product your installer sprays.

Closed cell foam is the opposite: the cells are sealed and densely packed together, so no air or moisture passes through. That makes the cured foam rigid, and the rigidity actually adds to the structural strength of the wall or roof it's applied to.

So why would anyone choose open cell? Because cell structure is only part of the story. A properly installed open cell system still creates an air barrier, and air sealing is the single most important part of your home's building envelope. (For a plain-English overview of insulation types, see the U.S. Department of Energy's guide.)

Density

Density follows directly from cell structure. Open cell foam typically has a core density around 0.5 pounds per cubic foot. Closed cell runs three to four times heavier, usually 1.75 to 2.2 pounds per cubic foot.

The lighter, softer structure of open cell foam is also why it outperforms closed cell at sound dampening: it absorbs sound waves far more efficiently than the dense, rigid closed cell material.

Expansion and R-Value

Open cell foam expands 100 to 120 times its sprayed volume. Closed cell expands only about 30 to 35 times. Closed cell typically delivers around R-6 to R-7 per inch, while open cell runs about R-3.5 to R-4 per inch.

Higher R-value per inch sounds like an automatic win for closed cell, but it isn't. The biggest cause of heating and cooling loss in a home is uncontrolled air leakage, not raw R-value. Both foams can create an air barrier when installed at the right thickness: closed cell at roughly 1.25 inches, open cell at about 3 to 3.5 inches.

Here's a worked example. In a typical wall cavity, 2 inches of closed cell foam gives you approximately R-14. The same cavity with 3.5 inches of open cell yields approximately R-13. Because both assemblies create an air barrier, conditioned air isn't leaking out and outside air isn't infiltrating in, so the real-world thermal performance of the two walls is virtually identical.

Cost

Closed cell foam costs more. It's denser, so it takes more material to cover the same area, and more material can also mean more labor. Open cell keeps costs lower while still delivering excellent coverage, especially in complex spaces with lots of nooks and crannies. (More background: Energy.gov's home insulation fact sheet.)

What Are the Benefits of Each?

Open Cell Spray Foam Benefits

• Lower cost. The material costs less to manufacture, and because it expands so much more, it takes less product (and often less labor) to insulate the same space.
• Superior coverage in tight spots. The high expansion rate fills every nook and cranny, which is exactly what you want for a proper air barrier in hard-to-reach framing.
• Moisture recovery (hydrophobic products). If a hydrophobic open cell foam gets wet from a leak, it can dry out and keep performing. Traditional insulation like fiberglass soaks up water and can lead to mold.
• No food value for pests. Spray foam isn't a pest deterrent, but it offers rodents and insects nothing to eat, so you won't find critter nests in it.
• Sound dampening. It insulates, seals, and quiets your home at the same time.

Closed Cell Spray Foam Benefits

• Higher R-value per inch. When wall depth is limited and code requires a specific R-value, closed cell reaches compliance in less space.
• Vapor and bulk water rejection. At appropriate thickness, closed cell acts as a vapor retarder and won't let bulk water pass. FEMA recognizes closed cell spray foam as flood-resistant insulation for flood-prone areas.
• Exterior application. Because it rejects water, closed cell can be sprayed on building exteriors when that's the best access point.
• Structural rigidity. Closed cell stiffens what it's sprayed on. Insulating a pole barn in an area with high winds? Closed cell helps combat metal panel flex.

Benefits You Get From Both

• A true air barrier, the most important factor in your home's energy efficiency. Spray-foamed homes routinely test far tighter than typical code requirements.
• Better indoor air quality. A sealed envelope keeps allergens, dust, and outdoor irritants from infiltrating.
• Smaller HVAC loads. In new construction, a spray-foamed envelope often lets you downsize the HVAC system, saving up front and every month after.
• No sagging or settling. Both foams adhere to the structure instead of sitting in the cavity, so performance doesn't degrade over time.

Open Cell vs Closed Cell at a Glance

So, Which One Should I Use?

It comes down to the application:

• Code requires high R-value in a shallow cavity? Closed cell reaches the number in less depth.
• Budget is the driver and the application allows it? Open cell delivers the same air-sealed performance at a meaningfully lower cost.
• Exterior application or possible water exposure? Closed cell. It rejects bulk water and is FEMA-recognized for flood-prone areas.
• Lots of hard-to-reach nooks and crannies? Open cell's expansion seals them efficiently.
• Metal building or pole barn in high winds? Closed cell adds structural rigidity along with insulation.

At their core, both open cell and closed cell foam accomplish the same mission: they seal your home, last for the life of the structure, and dramatically reduce heating and cooling costs. Many projects use both, closed cell where moisture or rigidity matters and open cell everywhere else.

Frequently Asked Questions

Is closed cell foam worth the extra cost?

Only when the application demands what closed cell uniquely offers: high R-value in limited depth, vapor control, water rejection, or structural rigidity. In a standard wall or attic where an air barrier is the goal, open cell delivers virtually identical real-world performance for less.

Can you use open cell and closed cell in the same house?

Yes, and it's often the smart play. A common approach is closed cell in the crawlspace or basement (moisture control) and open cell in the attic and walls (coverage and cost).

Which spray foam is better for a basement or crawlspace?

Closed cell, in most cases. Below-grade spaces see moisture, and closed cell's vapor-retarding, water-rejecting structure is built for it.

Does open cell foam really stop air leaks as well as closed cell?

At the right installed thickness, yes. Open cell reaches full air-barrier performance at about 3 to 3.5 inches versus 1.25 inches for closed cell. Both stop the air leakage that drives most energy loss.

Still Deciding? Let's Look at Your Project Together

Our certified team has insulated homes and buildings across Indiana and Kentucky since 1995, including Louisville, Indianapolis and Anderson, and Southern Indiana. Request a free assessment and we'll recommend the right foam (or combination) for your specific structure. Superior Insealators is an ABAA (Air Barrier Association of America) certified insulation contractor.