Fiberglass insulation is made from glass, much of it recycled, melted and spun into fine fibers. Those fibers trap pockets of still air, and still air is what slows heat moving out of your house in winter and into it in summer.
It comes in two forms. Batts are pre-cut blankets sized to fit between studs, joists and rafters. Loose-fill fiberglass, also called blown-in fiberglass, is the same material chopped into small tufts and blown into place by machine. Same material, different jobs. Batts suit open walls and framing you can reach. Blown-in suits attic floors, where it fills around joists, wiring and odd-shaped gaps that batts leave open.
Our crews in Falconer, NY and Cochranton, PA install both, along with spray foam and cellulose. That means we’ll recommend fiberglass when it’s the right material for the space, not because it’s the only thing on the truck.
That matters, because fiberglass isn’t the answer everywhere. In a rim joist or a crawl space that gets damp, spray foam does a better job. In an attic floor or an open wall, fiberglass is hard to beat on cost.
Fiberglass is spun from glass and sand, so it isn’t combustible. That makes it a safe choice around attic framing, recessed lights and chimneys, as long as the required clearances are kept.
The glass fibers don’t absorb water or give mold anything to eat. If a roof leak wets it, it dries out and keeps working once the leak is fixed.
Per dollar, blown-in fiberglass is one of the cheapest ways to get an attic up to the R-49 to R-60 recommended for homes in New York and Pennsylvania.
Most homes we see in Western New York and Northwest Pennsylvania are badly under-insulated in the attic. Typically that’s 4 to 6 inches of old, compressed material where there should be 16 inches or more. The attic is where most heat escapes, so it’s where an upgrade pays back fastest.
Blown-in fiberglass is our go-to for open attic floors. It goes on quickly, fills around joists and wiring without the gaps you get from cut batts, and settles very little once it’s down. We blow it to a measured depth and leave depth rulers in the attic so you can see what you paid for.
Before anything is blown in, the attic gets checked. Bathroom fans that vent into the attic, missing baffles at the eaves and old insulation that’s wet, moldy or rodent-damaged all need dealing with first. If the old material has to come out, our insulation removal crew clears it before the new fiberglass goes in.
Air leaks matter as much as depth. Gaps around plumbing stacks, wiring holes through the top plates and unsealed attic hatches let warm, moist air straight into the attic. Fiberglass slows heat moving through it, but it doesn’t stop air pushing past it, so the big leaks should be sealed before the fiberglass goes on top.
Walls are a different job from attics, and the right material depends on whether the wall is open or closed.
In open walls, such as new construction, additions, gut renovations and finished basements, we install fiberglass batts sized to the framing. That usually means R-13 or R-15 in 2×4 walls and R-19 or R-21 in 2×6 walls. The batts have to be cut tight around outlets, wiring and pipes. A batt jammed in or left short loses a surprising amount of its rated R-value, and it’s one of the most common faults in walls that were insulated in a hurry.
Closed walls in older homes need a different approach. Where the walls aren’t being opened up, we dense-pack them, usually with cellulose rather than fiberglass. We remove siding, drill a 2-inch hole into each cavity and blow the material in with air until the cavity is packed tight. See our blow-in insulation page for more.
R-value measures how well insulation resists heat flow, and the higher the number, the better. Blown-in fiberglass runs at roughly R-2.2 to R-2.9 per inch depending on the product. Batts carry their rating on the label.
For attics in New York and Pennsylvania, the US Department of Energy recommends R-49 to R-60. With blown-in fiberglass, that works out at roughly 16 to 22 inches of depth. If you can see the tops of your ceiling joists when you look into the attic, you’re well short of that.
Depth only counts if it’s installed properly. Compressed, gappy or wind-washed fiberglass at the eaves performs well below its label, which is why we install baffles and blow to a measured depth.
For walls, the code minimum for new homes in this climate is R-20 in a 2×6 wall, or R-13 with continuous insulation on the outside. That’s another reason walls are a design decision rather than a quick upgrade, and why we look at them case by case.
We price every job after seeing it, because a few things move the number. The biggest is the area and the depth you’re going to: topping up an attic from R-19 to R-49 is a different job from starting at bare joists. After that it’s prep. Air sealing, baffles, venting bathroom fans properly and removing old insulation all add time, and skipping them is how cheap insulation jobs end up failing.
Access matters too. A big, walkable attic is quicker than a low one with tight eaves. And batts in open walls are priced on the wall area and the framing size.
What we can say is that blown-in fiberglass is one of the most cost-effective upgrades you can make to an older home. Check our incentives page too, as rebates can take a real chunk off the cost.
Both are fiberglass. The difference is fit.
Batts are the right call where the framing is open and regular: new walls, basement walls, rafters in a finished attic, and floors over unheated spaces. Installed carefully, they’re tidy, predictable and easy to inspect. For batt installs, see our batt insulation services.
Blown-in is better on attic floors, especially older ones with uneven joists, wiring runs and lots of obstructions, because it fills every gap rather than leaving the slivers batts can’t reach. It’s also the easiest way to add depth over existing insulation.
Wondering about cellulose instead? It’s the other common blown-in material, and we install both. Our blow-in insulation page covers how the two compare.
Our New York crew works out of Falconer and covers Jamestown, Ellicottville, Gowanda, Hamburg, Olean, Mayville and Fredonia. See fiberglass insulation in New York.
Our Pennsylvania crew is based in Cochranton and covers Meadville, Erie, Franklin, Grove City, Hermitage, New Castle, Slippery Rock and Titusville. See fiberglass insulation in Pennsylvania.
We’ll look at your attic and walls, measure what’s there now and tell you what it would take to get to the right R-value. You’ll get a written quote with the material, depth and prep work spelled out. If fiberglass isn’t the best fit for the space, we’ll say so and explain why. Call the branch nearest you to book your free assessment.
