The short version
Spray foam is best when you need insulation and air sealing. Fiberglass is often a good choice when you need a more budget-friendly way to add thermal resistance.
Neither material is automatically better. The right choice depends on the space.
Side-by-side comparison
| Factor | Spray foam | Fiberglass |
|---|---|---|
| Air sealing | Strong, because it expands into gaps | Limited, air sealing must be done separately |
| Upfront cost | Usually higher | Usually lower |
| Moisture resistance | Better in many applications when installed correctly | Can lose performance if wet or compressed |
| Best uses | Attics, crawl spaces, rooflines, gaps, hard-to-seal areas | Attics, walls, floors, accessible spaces |
| Installation | Requires trained installers and proper equipment | More common and simpler in many applications |
| Comfort impact | Strong when air leakage is the issue | Strong when the main issue is insulation depth |
When fiberglass makes sense
Fiberglass can be a practical option when the space is accessible and the goal is to improve insulation levels without a more complex install.
It may be a good fit for attic floors, wall cavities, floors over unconditioned spaces, or areas where air sealing is already handled.
When spray foam makes sense
Spray foam may be the better choice when gaps and air movement are part of the problem.
That includes crawl spaces, rooflines, metal buildings, renovation areas, and attics where air leakage is making the home harder to cool or heat.
Do not choose by material alone
The biggest mistake is picking a material before understanding the building. A home with moisture issues, pest damage, poor ventilation, or old insulation may need prep work before any new insulation goes in.
A professional inspection can prevent wasted money.
Bottom line
Spray foam and fiberglass both have a place. Southern Insulation Company can inspect your home or business and recommend the material that fits the actual problem.
