Blown-In Insulation

Radiant barrier and blown-in insulation do different jobs. A radiant barrier helps reflect radiant heat (mainly summer attic heat), while traditional insulation (like blown-in) slows conductive heat flow year-round. Most homes get the best comfort and efficiency when radiant barrier is paired with proper attic insulation.

Blown-in insulation (also called loose-fill) is fiberglass or cellulose that’s installed with a blower to create an even, continuous blanket, most commonly across an attic floor. Homeowners like it because it fills gaps and irregular areas better than many older batt installs. It’s a popular upgrade when rooms feel uneven, the home is drafty, or energy bills are rising.

If you have hot/cold rooms, drafty ceilings, or high heating and cooling bills, blown-in insulation is often one of the best “comfort per dollar” upgrades, especially in an under-insulated attic. It helps create a more continuous thermal blanket, which can reduce HVAC run time and improve indoor comfort.

Cellulose is typically made from recycled paper treated for fire resistance, while fiberglass is made from spun glass fibers. Both can perform well when installed to the right depth and density, but the “best” choice usually comes down to your goals (budget, sound control, air-leak reduction) and the specific area being insulated.

In Florida this is simpler than most R value charts make it look, because we only deal with the warm end of the scale. Nearly all of the state sits in climate zone 2, with the far south in zone 1, so the Department of Energy puts our attics somewhere in the R30 to R60 range. For Central Florida, the target most homes should hit is R38, which is also the ceiling level Florida’s energy code calls for in new construction here.

What that means in inches depends on the material. Blown in fiberglass adds about R2.5 per inch, so reaching R38 takes roughly 14 to 16 inches. We blow slightly past the target on purpose, since loose fill settles over the first year, and we keep the depth even across the whole attic so there are no thin spots.

Blown-in insulation is one of those projects that looks simple, but getting good results depends on getting a lot of details right, including proper depth and coverage, and keeping ventilation paths clear. DIY can also get risky fast in attics because of heat, low clearance, exposed wiring, and the chance of stepping through the ceiling. A professional crew can handle baffles, recessed light clearances, and tricky areas so you do not end up with uneven coverage or hidden problems. For most homeowners, hiring a pro is the safer, cleaner way to get the performance you are paying for.

Some materials can settle over time if they’re not installed to the right depth/density, which is why proper installation (and hitting the marked depth) matters. Moisture problems usually come from roof leaks, bathroom fan venting issues, or poor attic ventilation, so you want those fixed before insulating. Blown-in insulation isn’t a “mold maker,” but it can hide problems if the attic isn’t dry and well-vented.

Not always. If the existing insulation is dry, clean, and not moldy or contaminated, many homeowners simply “top off” with blown-in insulation to reach the right depth. If there’s rodent damage, moisture issues, or you’re doing major repairs, removal can make sense.

Most attics perform best by adding enough insulation to hit an appropriate R-value for your climate zone. Blown-in insulation is common because it covers evenly and tops off older insulation well. The “right” recommendation depends on whether you’re insulating the attic floor or the roofline, plus ventilation and moisture conditions.