Fiberglass insulation is made from molten glass spun into fine fibers that trap air. That trapped air is what gives it its R-value — typically R-3.0 to R-4.3 per inch depending on density. It's non-combustible, doesn't settle when installed correctly, and costs roughly a third of spray foam per square foot of coverage.
The most important consideration with fiberglass is installation quality. Compressed, gappy, or improperly fitted batts can lose 20% or more of their rated R-value. That's why our crews are trained to inspect and grade installations to Grade I standards — the highest level recognized by ENERGY STAR and BPI.
For Chicagoland multifamily buildings, fiberglass is the right choice for new construction wall cavities, open attic floors, and any application where cavity depth is generous and moisture is well-managed.