Compare
Spray Foam vs Blown-In Insulation
The question is not which material is better, it is which one suits the space. In an open attic, blown-in usually wins on value. In a rim joist or a cathedral ceiling, it is not even a contest.
Side by side
| Criterion | Spray foam | Blown-in |
|---|---|---|
| Cost per sq ft | $1.50 – $5.00 | $2.00 – $3.50 including labour |
| Seals air on its own | Yes | No — needs separate air sealing |
| Best for | Rim joists, crawl spaces, knee walls, cathedral ceilings | Open attic floors |
| Settling over time | Does not settle | Cellulose settles; fibreglass largely does not |
| Fills around obstructions | Excellent | Good |
| Can go over existing material | No — surface must be clean | Yes, if the existing material is dry and clean |
| Install time, typical attic | 1 – 2 days | Often 1 day |
Spray foam makes sense when
- The assembly is irregular or hard to reach
- Air sealing and insulating need to happen in one step
- Depth is limited and R-value per inch matters
- The space touches unconditioned or damp areas
Blown-in makes sense when
- It is an open attic floor with room for depth
- You want the most R-value per dollar
- Existing material is sound and can be topped up
- The work should be done in a single day
Questions
Can I use both?
Most of our attic jobs do: foam to air seal the penetrations and transitions, blown-in for the field of the attic.
Is blown-in insulation a compromise?
Not in an open attic. Paired with proper air sealing it reaches R-60 at a fraction of the cost of foam.
Still not sure?
You do not have to decide. Tell us what the space is and what you want it to do — the recommendation is part of the free assessment, in writing, with the reasoning.
