The Difference Between Blown-In Insulation vs. Spray Foam

If you’re researching insulation options for your home, you’ve likely come across one of many product debates in today’s insulation industry—blown in insulation vs spray foam. 

Both products have merits and drawbacks, but how do you know which is best for your home? This guide breaks down everything you need to know about both products to help you choose the best option for your upcoming project. 

We’ll explore each type, describe what they’re made from, and discuss their advantages and disadvantages. We’ll also briefly examine cellulose insulation vs. spray foam and note other attic insulation options to consider for your project. 

Insulation 101

Before we get into the blown-in insulation vs. spray foam debate, let’s break down a few insulation essentials you should know while you shop.

Insulation is designed to prevent one or more types of heat transfer, which include:1

  • Conduction, or heat transfer between solids
  • Convection, the transfer of heat between liquids and gasses
  • Radiation, which travels in a straight line until it’s absorbed by a solid (like heat from the sun)

Insulation provides resistance against these types of heat—and its ability to do so is measured in resistance value, or R-value. The higher the R-value of an insulation product, the more effectively it can prevent heat transfer.

Why is it important to mitigate heat transfer in your home? Insulation plays two critical roles in your home HVAC system:

  1. It keeps hot air from leaking into your air-conditioned spaces during warm weather
  2. It prevents heated air from escaping into the attic during cold weather

While you can control your home’s temperature without it, insulation helps you manage your home climate efficiently—instead of overworking your HVAC system and racking up a large energy bill. 

Spray Foam Insulation

First, let’s dive into spray foam insulation—one of many insulation materials on the market today. Spray foam is available in various material types, each with its own set of pros and cons. 

Spray Foam Insulation Materials

Foam insulation can be applied in a few different ways—it can be:2

  • Sprayed
  • Poured
  • Injected
  • Foamed-in-place

In this section, we’ll focus on spray applications. While insulation installers can spray a variety of materials, two kinds of foam are the most common:

  • Closed-cell foam – is made of high-density cells and filled with gasses that help the cells expand, fill small spaces, and harden into a durable coating. 
  • Open-cell foam – isn’t as dense, and it doesn’t feature the expansion and hardening gasses that are found in closed-cell foam. Instead, the expanding cells fill with air, creating a sponger insulation texture. 

Both open- and closed-cell spray foams are typically made from polyurethane, but less common materials include Icynene and Tripolymer foams. 

Benefits of Spray Foam

Spray foam offers many benefits:

  • Spray foam is an air barrier. Since it can expand even into small spaces, it can completely block air flow where it’s applied. 
  • You can use it in small, canned quantities for a variety of home improvement applications, like filling gaps in window and door frames. 
  • It generally offers a higher R-value than batt or blown-in insulation, even at the same thickness or less. 
  • Like blown insulation, it can fill tight spaces or obstructed areas, like joists near an air handler or other HVAC equipment.
  • Some spray foam products (but not all) feature fire retardant properties that can help reduce or prevent fire damage. 

Drawbacks of Spray Foam

But, there’s no perfect insulation product—spray foam insulation certainly has drawbacks:

  • Applications – While closed-cell foam can be used in various locations, open-cell foam isn’t always appropriate for humid climates or applications below ground level. The air-filled cells easily absorb water, which can drastically degrade the insulation’s effectiveness. 
  • Cost – Both open- and closed-cell spray foam insulation are some of the most expensive insulation options on the market today. It requires specialized equipment to install and sometimes special installer certifications (depending on the specific product).
  • Building code recognition – While most building codes in the US recognize spray foam insulation as an insulation product, many don’t recognize it as a vapor or fire barrier. In these jurisdictions, builders must also install additional flame retardant and/or vapor barriers to pass inspection.

Depending on your budget, intended applications, and local building codes, spray foam insulation might not be the right fit for your next project. 

Blown-In Insulation

Now that we’ve broken down spray foam insulation, let’s jump into blown-in insulation. Like its competitor, it’s available in various materials and has its own set of benefits and drawbacks.

Blown-In Insulation Materials

Blown-in insulation (sometimes called loose-fill insulation), must be applied using specialized insulation technology, just like spray foam. An insulation installer uses advanced blower technology to apply small insulation particles to a space in a full-coverage layer that’s a consistent thickness throughout. 

Three different materials can be used in blown-in insulation applications, and they all feature some level of eco-friendliness:

  • Fiberglass is the most common insulation material on the market today, and it’s typically made from 40-60% recycled glass.
  • Mineral wool is losing traction in the insulation industry, and it’s not used as often today as it was in the past. It’s typically made from rock or slag recycled from industrial operations.
  • Cellulose is made from tiny paper fibers—usually recycled newsprint. While the performance of cellulose vs fiberglass insulation are comparable, installing it is a dusty proposition. 

All About Cellulose

So, what is cellulose insulation and how does it compare to other insulation types? Let’s explore a more specific debate—cellulose insulation vs. spray foam. 

Cellulose insulation can seem like an attractive option for homeowners looking to decrease their home energy use. Cellulose is eco-friendly (since it’s made from recycled material like newsprint), it’s only available as a blown-in product (so it can fill small nooks and crannies), and it offers comparable R-values to fiberglass insulation.3

But, it has three major drawbacks:

  1. It’s typically more expensive than fiberglass despite offering a similar R-value.
  2. It’s incredibly dusty to install, creating a potential health hazard to installers.
  3. It’s more prone to mold growth and water absorption than fiberglass. 

In terms of performance alone, spray foam insulation exceeds cellulose r value per inch. But, cellulose is markedly cheaper than both open- and closed-cell foams, and both are more expensive than fiberglass, which performs well, is durable, and is simple to install.

Advantages of Blown-In

Blown-in insulation (in any of the three materials listed above) does offer a few advantages:

  • Since it’s blown in, it can fill small gaps and hard-to-reach areas, like spray foam.
  • It’s available in fiberglass, the most commonly used insulation material.
  • It’s more cost-effective than spray foam and (depending on the material used) can fulfill a wider range of applications.

Blown-in insulation is versatile, eco-friendly, and economical—especially compared to spray foam insulation. 

Disadvantages of Blown-In

But, like spray foam, blown-in insulation also has drawbacks:

  • Specialty equipment demands – Blown-in insulation requires specialized blower equipment and installers trained to use it. This can sometimes lead to increased labor costs or hamper DIY insulation installation efforts. 
  • Settling – Like many insulation products, blown-in insulation settles with time. When a product settles, the size of the air pockets between particles decreases, which can also decrease the R-value of a product. Some materials settle more dramatically than others—cellulose is particularly prone to settling issues. 
  • Compression – Compression is similar to settling, but it’s more avoidable. When you step on your insulation or store boxes on top of it, the weight can tamp down the insulation, reducing the size of air pockets (and, thus, the R-value). Since blown-in insulation can be applied to joists in an attic space (instead of between them, like batts), it’s harder to avoid stepping on them while walking in your attic.

Which Insulation Type is Right for Your Home?

If you’re unsatisfied with both sides of the blown-in insulation vs. spray foam debate, rest assured—they aren’t your only insulation product options. 

While we covered two of the three application methods (spraying and blowing in insulation), one remains—batts, also called blankets or rolls. 

Batts are available in a variety of material types, but fiberglass and mineral wool are the most common. And, with the decrease in mineral wool availability, you’re most likely to encounter fiberglass batts in residential applications. 

There’s a lot to think about when choosing an insulation product, but remember to consider:

  • Your home’s overall condition – If you’re replacing the insulation with no plans to fix the leaks in your HVAC system, roof, or windows, you may have bigger fish to fry in pursuit of lower energy use.
  • Your budget – Not every budget can accommodate the most expensive products with the highest R-values. Instead of going over budget, savvy homeowners should choose the best product in their price range and focus on installing it well. 
  • Your local climate – Some insulation products simply aren’t suited to wet or very cold environments. Ask an insulation expert for advice on choosing the best product based on your local conditions. 

Attic Construction: Meeting Your Insulation Needs since 2011

There are countless combinations of insulation types and materials available today—so, how can you pick the best one? 

Consult with insulation professionals from Attic Construction. For over a decade, we’ve been helping homeowners choose the best possible insulation products, prevent pests, and get their attics shipshape. When it comes to improved quality of life and reduced home energy use, we’re the brand of choice for insulation installation, air duct repair, rodent  proofing, and attic cleaning in Orange County, Phoenix, and San Diego. We can’t wait to help you transform your attic, improve your temperature regulation, and increase your home’s value. 



  1. US Environmental Protection Agency. Insulation. 
  2. US Department of Environmental Protection. Types of Insulation. 
  3. HomeAdvisor. Comparing the Pros and Cons of Cellulose and Fiberglass Insulation.