What is blow-in insulation?
Blow-in insulation is loose material — either fiberglass or cellulose — that gets fed through a machine and blown into your attic through a long hose. It lands as an even blanket across the attic floor and fills in around joists, wires, light boxes, and all the other stuff that makes batt insulation hard to fit cleanly.
It works by trapping air in millions of tiny pockets. More pockets means more resistance to heat moving through. Fiberglass blow-in gives you about R-2.5 per inch. Cellulose (made from recycled paper treated with fire retardant) gives you about R-3.5 per inch and is heavier, which helps it resist air sneaking through the layer.
The biggest factor is how deep it goes. Most older homes around here have 4 to 6 inches of insulation in the attic — that is only R-11 to R-19. The Department of Energy says attics in our part of Alabama (Climate Zone 2) should be at R-38 to R-60. Blow-in is the fastest and cheapest way to get from where you are to where you should be.
When does blow-in make sense?
Blow-in is a good fit when:
- Your attic is not a living space — If nobody is up there and there is no important ductwork in the attic, insulating the floor is cheaper and easier than foaming the roof deck.
- Your current insulation is thin but still in good shape — If what you have is dry and not falling apart, we can blow new material right on top of it.
- You want a noticeable improvement without a big price tag — Blow-in costs a lot less per square foot than spray foam. For a basic attic floor job, it is one of the best values in home improvement.
- You are fixing up a rental or investment property — Blow-in gives you a real comfort boost at a price that makes sense for the return.
Blow-in is usually not the best first step when the attic has a lot of air leaks — things like can lights without covers, unsealed plumbing pipes, or open gaps where interior walls meet the attic floor. In those cases, we seal the leaks first, then blow insulation on top. We handle both parts.
How do we measure and install it?
We do not guess from the attic hatch. Before we quote anything, we go up and check:
- How deep the current insulation is at several spots across the attic
- Whether the existing material is still in good shape or damaged (wet, crushed, chewed up by rodents)
- Where the air leaks are — can lights, plumbing pipes, duct connections, and the top edges of walls
- How the attic vents — soffit vents, ridge vents, and whether they are open or blocked
When we install, we cover the attic access to keep material from falling into the house, set depth markers across the floor, and blow to the target depth we agreed on. When we are done, you can look at the markers and see that the coverage is even.
Should I pick fiberglass or cellulose?
Both do the job well. Here is how they compare:
- Fiberglass — Lighter, does not soak up water, and does not settle as much over the years. It is the go-to choice for most attic floors.
- Cellulose — Heavier, slightly better R-value per inch, and does a better job blocking air from moving through the insulation layer. The extra weight means it can put stress on older ceilings if blown too deep. It is also treated with borate, which helps with fire resistance and keeps bugs away.
We will tell you which one fits your attic better. The installation process is the same either way.