Technical comparison: Spray foam vs. Cellulose vs. Fiberglass – Which insulates better?

When it comes to choosing the best material for thermal and acoustic insulation, three options dominate the market: spray foam, cellulose, and fiberglass. Each has its advantages, disadvantages, and ideal applications.

In this technical comparison, we’ll analyze which one insulates better, considering thermal performance (R-value), air sealing, moisture resistance, sustainability, cost, and application method.

What is each type of insulation?

Did you know that up to 30% of the energy used to heat or cool a space could be leaking out through poorly insulated walls, windows, roofs, and 🔹Spray Foam
Applied by spraying and expands upon contact with air, sealing all gaps. There are two types: open-cell and closed-cell.

🔹 Cellulose
Made from recycled paper treated with fire retardants and fungicides. It is applied by blowing it into wall and ceiling cavities.

🔹 Fiberglass
Composed of fine glass fibers, available in batts or panels. It is the most traditional type of residential insulation.

Technical comparison

Which insulates better thermally?

If we consider thermal performance alone (R-value), closed-cell spray foam clearly leads. It offers up to twice the thermal efficiency per inch compared to fiberglass or cellulose. Plus, its superior air-sealing ability boosts performance even further.

Air and moisture sealing: Spray foam’s key advantage

Another major advantage of spray foam is its ability to completely seal cracks and gaps—something cellulose and fiberglass can’t achieve on their own. This means less heat loss in winter and reduced hot air infiltration in summer, potentially cutting energy bills by up to 50%.

Sustainability: A win for cellulose

Cellulose stands out in terms of sustainability. Made from recycled materials (typically newspapers and cardboard), it has a lower carbon footprint and reduced environmental impact during manufacturing.

Cost-effectiveness: Depends on your priorities

• If you want maximum thermal efficiency and airtight sealing, even at a higher cost: spray foam is ideal.
  
• If you want good performance with environmental focus and a mid-range budget: choose cellulose.
  
• If your budget is tight and you plan to do it yourself: go with fiberglass, but be sure to install it correctly to avoid performance losses.

Conclusion: Which one should you choose?

There’s no one-size-fits-all answer—it depends on your project type, local climate, budget, and priorities.

Final tip: Combine materials

In some projects, combining materials may offer the best cost-benefit ratio. For example, use spray foam to seal gaps and cellulose or fiberglass to fill the rest.

Before deciding, consider a thermal assessment of your home. A professional can recommend the most efficient and cost-effective solution for your case.