Open-cell vs closed-cell insulation foam: R-values & DIY kits

If you’re installing insulation in a home, there are some things you’ve got to know. Maybe you’re building that dream home you’ve always wanted.

The contractor you’re working with has been telling you a bunch about your options. 

foam insulation in a big building

Maybe you’ve started looking into foams, and you’ve come across both open-cell and closed-cell insulation foam. What are their R-values?

When is it a good time to use one versus the other? It’s not quite as simple as it may seem. In terms of how they insulate, it depends on the type you choose.

So, what’s the best option? 

We’ll make sure you understand the differences by the end of this article so that you can make the best decision for your home. 

Open-cell vs. closed-cell insulation foam: What are the differences?

foam insulation

Spray foam isn’t a one-product kind of material. There are various options for you to choose between. One type has advantages, while the other one has weaknesses and vice versa.

The best kind will depend on your needs, as there’s not one that’s universally better than the other.

Choosing the right type for your home or other projects will depend on your needs. 

Without knowing their differences, it’s hard to tell which is better in your situation. 

Let’s take it back a step further and look at the various types and some of their differences.

Types of spray foam insulation

house with foam insulation

Spray foam is a great insulating material that comes in various types. It can be used as a retrofit job, but it’s also great for new construction. When you’re adding additional insulation to that 1950s house, you know it’s a great investment when you choose it. 

With its high R-value and air barrier properties, you’re getting something that’s effective and easy to use. 

With other types of materials, it can be hard to seal everything off properly. Gaps in the wall may stay open and leave mice running around in the walls. Sealing walls properly isn’t just important to deter mice from running around. It’s also important for insulating purposes. 

The better you can fill the gaps and holes, and the lower your AC bill will be. As a consequence, you’ll also be able to go longer before having to replenish the refrigerant

Besides, properly insulating your home is also good for the environment. If you’re using other types of insulation, you might be missing out on 5,638kWh of energy savings per year that you could be getting. It’s the equivalent of a 33% reduction in your car’s annual emissions. 

Properly making sure that heating and cooling isn’t leaving your house unintentionally is the first way to reduce your carbon footprint. It could also help better soundproof your house, so you’re not getting annoyed when the neighbor is throwing loud barbeque parties.

Without further ado, here are the 3 types we’ll be getting into. 

house with SPF


Low density, open-cell insulation foam is the lightest of the 3 types we’ll get into. At 0.5 lbs per square foot, it’s not very heavy. It’s generally something you would put in unvented attics and interior wall cavities. 

It has R-values that start at 3.6 per inch. 

It can be used for continuous insulation and wall cavities. It provides a great air-sealing barrier and can close up holes that other materials may struggle with. However, it’s important to know that it also has certain limitations and isn’t ideal for exterior purposes. 

Low or high-pressure, two-component SPF is applied. While it provides continuous insulation, its cell structure gives it flexibility compared to other materials. 

Moisture and vapor can penetrate it, even if it provides an air barrier. For that reason, it’s often used in ducts and ceilings. However, it’s rarely used for exterior walls. 

It consists of resin and polyisocyanurate that are kept apart before being applied. They sit in separate drums until they are applied. At that point, both materials go through a heated hose where they are mixed. The foam that comes out hardens quickly. 

The cells of this material aren’t completely closed, and its structure has more of the property of a sponge. 


  • Its softer texture provides greater soundproofing. 
  • Structural strain isn’t an issue with the weight it adds to the walls.
  • Hard-to-reach places are easier to reach with open-cell insulation foam because it expands as much as it does. Closed-cell insulation expands only a third of the amount that open-cell does. For that reason, it’s more effective for cracks and crevices. 
  • Its flexibility provides certain advantages. When the temperatures change outside, the various materials are also affected by those temperature changes. Repeated hot and cold seasons make materials expand and contract, meaning they will settle after many seasons. The flexibility that open-cell provides makes it better at adjusting to those alternating seasons. 
  • It’s more environmentally friendly. Closed-cell products use chemicals as the spraying agent, whereas open-cell uses water. Those chemicals contribute to global warming, so open-cell is more environmentally-friendly. 
  • Commercial builds and theaters use it for its soundproofing properties. 
  • Open-cell is more affordable than closed-cell.


  • It dries very quickly. It shares that feature with epoxy grout, so you’ll have to work quickly. It expands quickly and dries quickly. For that reason, it’s easy to miss spots that should have been insulated. 
  • It may shrink over time. Exposed areas can arise if the material starts shrinking. Applying tape can help provide protection against the problem, but it’s still less than ideal. It’s yet another reason why it’s not ideal for exposed exterior walls. 
  • It provides no structural support.
  • It provides little protection in case of extreme temperatures. With its low R-value, it only works in moderate climates. Colder and hotter climates would do better not use this material in many situations. 
  • It may not meet building regulations if installed on the exterior walls. 

With its introduction in the 1980s, it is a material that serves a purpose. 


Medium density, closed-cell insulation foam is 4 times as heavy as low-density is. It weighs 2 lbs per cubic foot. With R-values starting at 5.7 per inch, you’re getting a material that is better suited for more demanding circumstances. 


SPF foam

High-density is a closed-cell foam that’s 6 times as heavy as the low-density material. It weighs a startling 3 lbs per cubic foot, and you get R–values that start at 5.5 per inch. 

This material will most commonly be used for exterior walls and roofing applications. With its greater insulating capabilities, it lends itself to other purposes. A blowing agent is used to fill the bubbles left open in open-cell foam. 

With the blowing agent comes a better thermal barrier that gives it its higher, insulating properties. It also doesn’t breathe the same way that open-cell insulation does. Once cured, you’ve got a much firmer and less flexible material. It doesn’t breathe the same way that open-cell foam does. 


  • Better insulating properties with R-values going as high as 7.14 per inch. 
  • Useful for subgrade foundation.
  • It doesn’t absorb water.
  • Its density adds strength to the structure, like roofs and ceilings. 
  • Drafts are prevented due to the material’s density.
  • Humidity is kept lower because temperature control is more easily done with this material. 
  • Once cured, it resembles solids. 
  • Compared to other insulating products, you’re getting something with a long lifespan. The cost benefits become obvious as the material is installed for several decades. 
  • As other types of insulation deteriorate over time, their R-values will fall. They’ll get less good at the job they were installed to do. Properly installed foam insulation will not fall out of place and will be able to keep its ability to keep your cooling bill low. In comparison, fiberglass has an R-value of 2.2 for non-aged material. As we mentioned, the same value for closed-cell foam is upward of 7.14. This number does not fall over time, whereas it does for fiberglass. Fiberglass usually needs to be replaced after 10 years, and that is assuming it manages to stay dry. 
  • Contaminants are kept out with the air barrier that is created. You will still need to take precautions and make sure that the air filter is changed as it should be, but the insulation helps. 
  • Your HVAC system won’t need the same capacity requirements due to a better-insulated home. Maintenance and wear on your HVAC system will be limited for that reason, which is an additional cost saving. 
  • Water damage will not affect the foam, which is known to happen with fiberglass.


  • Bacterial growth can happen because it’s unable to “breathe” excess moisture. Mold is a definite possibility. It can eat away at wood, leaving structural integrity vulnerable. 
  • The higher density makes it harder to remove excess afterward.
  • The cost is often higher than installing other types of products, although cost savings are achieved over the long haul
  • Water damage is a bigger possibility. With a breathing material, water can escape. However, improper installation can have various downsides. You’ll want to get a reputable insulation company to do the installation so that water pooling doesn’t happen. Air has a way of getting into places it shouldn’t be, and pressure can cause water to seep in as a consequence. Premature damage can happen to roofs and walls if water starts pooling. Unfortunately, it is very hard to determine if this occurred before water spots are obvious. It typically makes it hard to claim it to your insurance company for that reason, and you’re then left having to foot the bill. 
  • Other types of insulation are easier to install. With both types of foam insulation, you have a material that takes a short amount of time to cure. It means a contractor will have to act fast once the process is in motion. With its limited expansion, it is more of a problem for open-cell material. However, closed-cell insulation is harder to install than fiberglass. 
  • As it expands, unfilled areas can emerge. They can often be hard or impossible to see. Without attention to detail, whole sections may not get the material they were supposed to receive. 
  • It is significantly cheaper to install fiberglass throughout the United States. The material often costs many times what you would be paying for fiberglass.
  • Isocyanates can irritate the lungs and eyes if you get in contact with it. It is very important to wear the necessary safety gear to make sure you’re not getting in contact if you’re the installer. It includes a respirator, goggles, and gloves. Chemical bronchitis and asthma attacks are also known to occur with long-term exposure
  • You will want to avoid it as it’s curing. After it’s done curing, it’s not a problem at all. However, during the curing stage, a gas is emitted. Blurred vision and respiratory distress are known side effects. 
  • It doesn’t provide the same soundproofing properties provided by open-cell.
  • This material is even more expensive than open-cell material. 

Closed-cell spray foam kits

There are various closed-cell spray foam kits out there. If you are determined to do it on your own, you must take the time to familiarize yourself with the trade. 

The fast curing times give you very little time to remedy situations that have gone wrong. You will also know that it requires you to wear certain protective equipment to keep you from inhaling and getting in contact with gases that could be damaging to your health. 

In the following section, we elaborate on why we don’t think it’s worth it. 

However, it doesn’t change that there are kits out there that you can use to do it yourself. 

One popular DIY, closed-cell spray foam kit is the one from Froth-Pak that provides up to 650 board feet of insulation.

With the kit from Froth-Pak, you’ll get everything you need. There’s a container of isocyanate and a tank of polyol. There’s also a 15-feet hose, including everything to dispense the product. 


DIY closed-cell spray foam installation – is it worth it? 

No, DIY closed-cell spray foam installation is not worth it. 

Whereas it’s easy to see when you’re making a mistake when it comes to your DIY deck railing job, the nature of expanding foam makes it very hard to see when you’ve done an improper job. Without doing it properly, you won’t get the R-values you were promised. Your house will be leaking expensive, cold air!

Is closed-cell foam better than open-cell?

When it comes to exterior purposes, closed-cell foam is better than open-cell. When it comes to interior walls, the answer is the opposite. It all depends on the purpose it is being used for. 

Is open-cell foam insulation worth it?

Open-cell foam is great for keeping your hot air in the winter from going up into the attic while doing the same to the cold air in the summer. It’s worth insulating the attic to keep your energy bill low.

What is closed-cell foam good for?

Closed-cell foam is great for exterior surfaces and other places where building codes are stricter. It’s also great for harsher climates where the temperatures are more volatile. 

Hopefully, you can now understand the differences between the two products and when they’re right to be applied. In addition, we hope it helped shed some light on whether or not you should choose foam over other alternative products. 

We encourage you to get proper coveralls and the right respirator for the purpose as well.