Choosing insulation is one of the most important decisions you can make for comfort and energy bills, especially with Massachusetts winters. The two most common options are spray foam and fiberglass. Here is how they compare.
How Each Material Works
Fiberglass is made of fine glass fibers and is installed as batts (pre-cut panels) or blown-in loose fill. It slows heat transfer by trapping air between the fibers.
Spray foam is applied as a liquid that expands and hardens in place. It insulates and seals air leaks at the same time, filling gaps, cracks and irregular cavities.
Comparison at a Glance
| Spray Foam | Fiberglass | |
|---|---|---|
| Upfront cost | Higher | Lower |
| R-value per inch | About R-3.5 (open-cell) to R-6.5 (closed-cell) | About R-2.2 to R-4.3 |
| Air sealing | Excellent | Limited (needs separate air sealing) |
| Moisture resistance | Closed-cell resists moisture | Can lose performance when wet |
| Best for | Rim joists, basements, crawl spaces, hard-to-reach areas | Open attics, standard wall cavities, budget projects |
When Spray Foam Makes Sense
- You have drafts and air leaks that make rooms uncomfortable.
- You are insulating a basement, crawl space or rim joist where moisture is a concern.
- Space is limited and you need the highest R-value per inch.
When Fiberglass Makes Sense
- You have an open, accessible attic that needs more depth.
- Budget is the main priority.
- Walls are already open during a renovation.
What About Massachusetts Winters?
Massachusetts falls in climate zone 5, where ENERGY STAR recommends attic insulation levels of R-49 to R-60. Many older homes in Lowell, Boston and Worcester fall well short of that. In many cases the best result combines both materials: spray foam to seal leaks in critical areas and fiberglass to add depth in the attic.
Get a Professional Recommendation
Every home is different. Greensource Insulation inspects your home and recommends the right material for each area. Request a free estimate or call (617) 388-7649.