Spray Foam vs. Fiberglass Insulation: A Quick Comparison

Researched & Written by Craig

You’re taking the plunge and have decided: It’s time to insulate your home.

Whether due to loathsomely high energy bills, uncomfortable temperature fluctuations, mold growth, pest infestation, damage to the structure of your home ﹣ or all of the above ﹣adding or replacing your insulation can go a long way for your peace of mind and the integrity of your property.

But here comes a common dilemma that can arise for many homeowners:

Spray foam vs. fiberglass insulation… Which is the better choice?

Of course, both options have their pros and cons when it comes to installation, energy efficiency, cost, and return on investment (ROI). You may even have a few suggestions you’re considering; but what may work in your neighbor or friend’s home may not be suitable for your home’s unique needs.

To help you make the best choice, we’re hashing out the debate, once and for all:

So, spray foam or fiberglass insulation? You decide!

What Is Fiberglass Insulation?

You’ve probably seen it before; pink fluff sticking out of an unfinished wall or attic ceiling.

That wasn’t cotton candy. Rather, it was fiberglass insulation, and its delicate fibers come from melted down glass, rock wool, and other recycled particles.

These fibers work by trapping air and slowing down the movement of cold and hot air flow, as well as the sounds of creaky floors, vibrating walls, and overhead steps.

How much does it cost to install fiberglass insulation? The average cost can range anywhere from $1,000 to over $2,300, but can be higher when insulating a larger property.

How Is Fiberglass Insulation Installed?

Fiberglass insulation comes packaged as either pre-cut batts (or rolls) or loose-fill ﹣ and they are not quite the same.

Batt Insulation (Rolls/Blankets)

Fiberglass insulation typically comes as rolls or blankets; in layman’s terms, these are known as batts.

Pre-measured batt insulation is readily available and cut to fit between standard attic joists and wall studs. This is one of its greatest appeals; homeowners can simply roll it out and place it in their walls, attic, or crawlspace.

Fiberglass installation
When installing fiberglass ensure to wear gloves to prevent irritation

But there is one other factor when it comes to choosing the right batt insulation: Should you go faced or unfaced?

Faced insulation refers to a vapor barrier, which is essentially a sheet of paper or plastic that attaches and faces one side of the batt.

Why does the vapor barrier matter? What are the benefits? The vapor barrier prevents moisture from traveling through the insulation and further seeping into the walls or surface of your home. It can prevent condensation, mold growth, and other structural problems.

Faced insulation is generally recommended for exterior walls, ceilings, floors, and crawl spaces where there is no existing insulation.

**A quick word of precaution: Fiberglass insulation can irritate the eyes and skin if not handled properly. If you plan to handle batt insulation, wear safety work gloves, loose-fitting clothing, goggles, and a dust mask**

Blown-In, Loose-Fill

Loose-filled, pellet-like fiberglass insulation comes in bags, ready to make their way into the walls, attic, and nooks and crannies of a house with the help of a specialized electric blower.

You may be wondering, “Why go through all the trouble to install loose-fill when you can lay out the rolls of insulation yourself?”

For starters, not all attics and crawl spaces have enough headroom for a seamless installation. Some attics and crawl spaces also have problematic, tough-to-reach areas, or obstructions that make it difficult to lay out batt insulation.

Loose-fill is also a viable option for those who are looking to add to existing insulation or target specific sources of air leaks and moisture. Because loose-fill insulation is a job for the professionals, you can guarantee your attic, crawl space, or basement receives the correct density and amount of loose-fill, as well.

Many contractors, home improvement gurus, and DIY homeowners will even argue that blown-in insulation is more effective than traditional batt insulation. While it may cost more to hire a professional installer, the flexibility of the blown-in, loose-fill variety may work better against certain installation challenges.

Now that we understand some of the advantages and disadvantages of fiberglass insulation, let’s explore another important area.

Breaking Down R-Value & What It Means

Not all fiberglass insulation has equal thermal resistance. Fiberglass insulation comes in a range of densities, and every individual fiberglass insulation material﹣batt or loose-fill﹣has an R-value.

R-value measures performance and resistance to thermal energy. Fiberglass insulation with a higher R-value has greater insulating capacity.

In climates where harsh winters and blazing hot summer climates are the norm, most homes contain the thickest fiberglass insulation with the higher R-value. In the image below, you’ll see how the US Department of Energy has divided different regions of the United States into zones with respective R-value recommendations.

R-value recommendations map
R-value recommendations from the US Department of Energy

Knowing which R-value your region calls for is a good place to start; but R-value should not be the single deciding factor.

The bottom line? Your fiberglass insulation should better accommodate your home’s specific needs. If you don’t insulate the right areas, it won’t make the difference you’re seeking.

It also won’t make a difference if you’re not installing the right type of insulation, and that’s where spray foam insulation can come into play.

What Is Spray Foam Insulation?

Have you ever gone up inside an attic and discovered what looked like the inside of an igloo?

This surely was no igloo. Spray foam, made from a combination of isocyanate, polyol resin, and polyurethane, is a popular insulation material you can find in most new homes and buildings today.

Spray foam’s air-tight seal is its greatest appeal. As a result of this air-tight seal, the spray foam insulation substantially reduces the flow and infiltration of hot and cold air into a home. Compared to fiberglass insulation, spray foam insulation also provides a tougher and more effective sound and moisture barrier.

Spray foam insulation didn’t emerge in houses and buildings until the 1980s, but polyurethane has been around since the days of World War II. The military used polyurethane in their airplanes for its durability, tight seal, and strong resistance to heat, chemicals, corrosion, and noise.

The majority of newer homes and buildings today contain spray foam insulation, and even existing homeowners are opting to insulate their older houses with it. Spray foam comes in a variety of R-values, some of which are the highest on the market today. And on average, the cost ranges from $1200 to over $3500, which is subject to fluctuate depending on how large the space is.

So, how does it work exactly, and are there different kinds of spray foam insulation? Let’s find out.

How Does Spray Foam Insulation Work?

Often applied in open cavities, like attics, crawl spaces, and newly constructed homes, spray foam insulation takes about 24 hours to cure. During this curing time, the foam expands and dries between the structure and building materials of the open cavity, providing an air-tight seal in even the toughest-to-reach nooks and crannies.

There are two types of spray foam insulation to keep in mind when deciding between fiberglass insulation vs spray foam insulation.

Open-Cell Insulation

Open-cell spray foam is a very lightweight material with considerable sound-absorbing qualities. Applied with a hose and water as the blowing agent, open-cell foam fills in gaps and cavities where air leaks can occur. As it expands, it can better regulate temperatures, block moisture, and prevent condensation.

Open-cell spray can prevent minor water leaks, but it is not an effective deterrent against flooding and mold growth. Yet, in most standard homes, open-cell spray foam insulation can significantly improve energy efficiency as effective as fiberglass insulation﹣if not better.

Closed-Cell Insulation

Do you live in an area that’s prone to stormy weather and flooding? Do you own a warehouse or commercial space?

Closed-cell insulation works similarly to open-cell foam, but because it has a lower expansion rate and higher R-value, it makes for a better temperature controller. Tough, durable, and water-resistant, closed-cell foam provides a near-perfect air-tight seal and can endure extreme weather, deter mold growth, and block out moisture completely.

Closed-cell insulation also utilizes water in the installation process; however, closed-cell foam contains chemical components, and this can be one of its drawbacks for chemical-conscious homeowners. And because closed-cell foam involves chemicals, the installation requires the help of professional installers.

Is Spray Foam Insulation Right for Your Home?

Spray foam’s ability to expand and insulate the tightest of spaces makes it a superior option to other types of insulation. Though it is on the pricier side and may not appeal to budget-conscious owners, it can provide the biggest bang for your buck﹣and even improve the value of your property should you decide to sell.

Spray foam used in the attic
Spray foam is well suited to tight spaces like the attic because it can expand to fill small gaps

If you own commercial or industrial property, spray foam insulation can better protect your investment for the long-term. For homeowners, spray foam is also a viable option if the costs of materials and installation fits within your budget.

Spray Foam vs. Fiberglass Insulation: Which Is Better?

Affordable and energy-efficient, fiberglass insulation has long been a popular insulation material since the early 20th century… and it’s also one of the easiest insulation materials to install, for all you DIY-ers.

Though on the pricier side, spray foam is a newer type of insulation that performs higher and insulates home more efficiently than traditional fiberglass.

If you’re planning an insulation project on a budget, fiberglass insulation may be the more cost-effective option; but if you’re willing to spend a little more and extend the lifetime of your investment, spray foam insulation is the stronger option.

So there you have it! For more insight and tips on home improvement, check out our blog!