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Spray foam and fiberglass insulation side by side.

Insulation plays a pivotal role in the energy efficiency and comfort of buildings, be it residential or commercial. The right insulation can significantly reduce energy costs, enhance indoor air quality, and increase the overall comfort of the building’s occupants.

With several insulation options available in the market, this article will walk you through a comparative analysis of two popular choices: spray foam and fiberglass insulation. Understanding their characteristics, applications, and benefits will guide homeowners, builders, and contractors in making informed decisions.

Understanding Insulation Materials

What is Spray Foam Insulation?

A new home with spray foam insulation in progress.

Spray foam insulation is a chemical product created by mixing and reacting two materials that expand on contact to form a foam. This expansion allows it to fill gaps and crevices, providing an excellent air barrier. It comes in two primary types: open-cell and closed-cell, each with distinct properties and applications.

Types of Spray Foam Insulation

Open-Cell Spray Foam: Lighter, less dense, and more flexible, open-cell foam is ideal for interior applications, offering superior sound absorption.

Closed-Cell Spray Foam: Denser and more rigid, closed-cell foam provides added structural strength and better moisture resistance, suitable for both interior and exterior applications.

What is Fiberglass Insulation?

a wall being insulated using fiberglass batts.

Fiberglass insulation, made from fine glass fibers, is one of the most common and widely used insulation materials. It’s available in batts, rolls, or loose-fill, making it versatile for various applications.

Forms of Fiberglass Insulation

Batts and Rolls: Pre-cut or rolled sections fit between studs, joists, and beams, ideal for new construction.

Loose-Fill or (Blown-in Insulation): Small chunks of fiberglass blown into spaces, perfect for retrofitting areas with irregular shapes.


Comparative Analysis: Spray Foam vs. Fiberglass Insulation

1. Cost Comparison

Spray foam insulation cost might seem a bit high at first glance. Yes, it does require a specialized team to install, and the materials themselves aren’t cheap. But here’s the kicker: this type of insulation can be a real money-saver over time. Thanks to its high R-value and ability to snugly fit into tight spaces, spray foam keeps your energy bills lower by doing an ace job of keeping your indoor temperature steady.

On the flip side, fiberglass insulation is the go-to for a more budget-friendly upfront cost. Installing fiberglass insulation is also easier (you might even DIY it), and it doesn’t hit your initial budget as hard. But, and it’s a big but, fiberglass might not be the champion in the long run.

It needs to be thicker to match the insulating power of spray foam, and if it gets squished or develops gaps, you could be looking at rising energy bills.

An attic being insulated with blown-in fiberglass

2. Thermal Performance and R-Value

The thermal performance of insulation is crucial for maintaining a building’s temperature, with the R-value—a measure indicating resistance to heat flow—playing a pivotal role.

Spray foam insulation stands out for its superior R-value per inch, typically ranging between R-6 to R-7.1, offering better thermal resistance than fiberglass batts insulation, which generally falls between R-2.2 to R-4.3 per inch. This higher R-value of spray foam allows for thinner applications and provides flexibility in tight spaces.

Loose-fill fiberglass, used for attic insulation and other spaces, offers R-values ranging from R-2.2 to R-2.7 per inch. The performance of loose-fill fiberglass can be compromised over time by settling and compaction, which can reduce its thickness and, consequently, its R-value, requiring insulation top-up to sustain the insulation effectiveness.

2. Air Leakage and Moisture Control

Spray foam insulation is your go-to for sealing up those pesky air leaks and locking out moisture, expanding to fill every nook and cranny for a snug seal.

It’s especially great when you opt for the closed-cell type, which is a real powerhouse against moisture, doubling as insulation and a vapor barrier. This means you’re less likely to face issues with mold or mildew, and it helps keep your building solid and the air inside clean, making your space comfortable and energy-efficient.

On the other side, fiberglass insulation is a bit more traditional, doing a decent job at keeping the warmth in but not quite stepping up when it comes to blocking air and moisture.

Without adding extras like vapor barriers or house wraps, it might let in drafts and dampness, which could lead to higher energy bills and potential moisture woes. If you’re leaning towards fiberglass, be prepared for some additional steps to ensure it’s performing at its best, keeping your space cozy and dry.

3. Installation Process and Ease of Application

A man installing pink fiberglass insulation batts.

The installation process of fiberglass batt insulation is generally straightforward, particularly with batts that are designed to fit standard wall cavities. This ease of installation makes it a popular choice for DIY projects and reduces labor costs for professional installations. However, achieving optimal performance with fiberglass requires careful placement to avoid gaps and compression, which can compromise its insulative properties.

Spray foam insulation requires a more meticulous and controlled application process, typically performed by skilled professionals. The installation involves mixing and spraying chemicals on-site, which expand to form the insulative barrier. This process allows for a custom fit to the building structure, sealing off irregular shapes and sizes but at the cost of higher labor and material expenses.

4. Durability and Lifespan

Spray foam insulation’s resilience is one of its standout features, maintaining its shape and insulative properties without sagging or settling over time.

This enduring performance ensures long-term energy savings and minimal maintenance, making it an attractive investment for property owners seeking durability. Furthermore, the resistance of closed-cell spray foam to water absorption contributes to its longevity and structural support, enhancing the overall lifespan of the building components it insulates.

Fiberglass insulation can experience degradation over time, such as settling or sagging, particularly if not installed meticulously. These changes can diminish its insulative effectiveness and may necessitate additional insulation or repairs, impacting the overall cost-effectiveness and efficiency of the insulation over its lifespan.

While fiberglass is inherently durable, its performance is contingent on proper installation and environmental conditions, which can influence its longevity and effectiveness.

5. Environmental Impact and Sustainability

A technician is professionally spraying spray foam insulation to the walls.

Environmental considerations are integral when evaluating insulation materials.

Fiberglass insulation is notable for including recycled content and being recyclable at the end of its life, which contributes to resource conservation and waste reduction. However, the energy-intensive manufacturing process of fiberglass and the potential for fiber release into the environment during installation or removal pose environmental challenges.

Spray foam, while offering significant energy efficiency benefits, has its environmental drawbacks, particularly concerning its production and application processes. The chemicals used in spray foam can emit VOCs during application, impacting indoor air quality and posing health risks.

Moreover, the longevity of spray foam can be a double-edged sword, as its durability makes it less susceptible to recycling or decomposition, raising concerns about its long-term environmental footprint.

6. Health and Safety Considerations

The installation of fiberglass insulation necessitates protective gear, such as gloves, masks, and long-sleeved clothing, to prevent skin, eye, and respiratory irritation from glass fibers. Proper safety measures during installation and handling can mitigate these risks, but they remain a concern for installers and occupants if fibers are disturbed.

Spray foam insulation’s chemical components necessitate strict adherence to safety protocols during application to avoid exposure to toxic substances. Professional installers typically wear full protective gear and use

Application Scenarios

Best Uses for Spray Foam Insulation

Complex Architectures: Spray foam insulation offers the ability to conform to any shape making it ideal for buildings with irregular spaces or intricate designs.

High Moisture Areas: Closed-cell spray foam’s moisture resistance is beneficial in regions with high humidity or buildings prone to water intrusion.

Energy-Efficient Constructions: For projects where energy efficiency is a top priority, the higher R-value of spray foam can contribute to lower heating and cooling costs.

Best Uses for Fiberglass Insulation

Cost-Effective Projects: When budget constraints are a concern, fiberglass insulation offers a more affordable solution.

Standard Construction Projects: In structures with standard spacing between studs and joists, fiberglass batts and rolls can be quickly and easily installed.

DIY Projects: Homeowners looking to undertake insulation projects themselves may find fiberglass more manageable than spray foam.


Choosing between spray foam and fiberglass insulation involves considering multiple factors, including thermal performance, cost, application, and environmental impact.

While spray foam offers superior insulation and air sealing capabilities, its higher cost and need for professional installation may not suit every project.

Conversely, fiberglass provides a cost-effective, user-friendly option, especially for standard building designs and DIY projects.

Ultimately, the decision should align with the specific needs of the building, the project’s budget, and the long-term goals of energy efficiency and comfort. By weighing the advantages and disadvantages of each insulation type, builders, insulation contractors, and homeowners can select the most appropriate material for their needs, ensuring a comfortable, energy-efficient, and sustainable environment.