A plain-language comparison of the four insulation materials you'll actually see in a residential attic — and the situations each one fits best.
"Insulation" isn't one thing — it's a category of materials that all slow heat flow but do it differently. The four types you'll encounter in a residential attic are fiberglass batts, blown-in cellulose, spray foam, and rigid foam board. Each has a different R-value per inch, a different price point, a different installation method, and a different set of strengths.
This page is for homeowners who want a clean side-by-side of what those four materials actually are, how they behave in a real attic, and which one tends to make sense for which kind of home and budget. No sales pitch. No deep technical dive. Just what you need to know before scheduling a real inspection.
Pre-cut blankets of spun glass fiber, friction-fit between joists or studs. Cheap, familiar, and the default in many tract homes — but only performs well when installed perfectly with no gaps or compression.
Recycled paper fiber treated with boric acid, pneumatically blown into the attic to a target depth. Conforms to every gap and cavity, packs denser than batts, and resists pests and fire thanks to the treatment.
Liquid polyurethane that expands and hardens into a continuous air-sealing layer. Highest R-value per inch of the four and seals gaps as it insulates — but it costs significantly more and changes how the attic handles ventilation.
Flat panels of XPS, EPS, or polyiso foam cut to fit and sealed at the seams. Best where you need insulation in a thin profile — sloped ceilings, knee walls, garage ceilings, or exterior sheathing — rather than bulk coverage of an open attic floor.
There's no universal "best" — just the right material for your attic, your climate, your budget, and what your existing insulation is doing today. A few practical guidelines a Stravix inspector uses during a real walk-through:
The attic is open, accessible, and you're topping up what exists or replacing worn batts. Cellulose handles Virginia attic conditions well, gets into the corners batts miss, and the boric acid treatment deters pests and slows fire spread. This is the default for most Stravix residential attic upgrades.
You need a DIY-friendly, low-cost material for a small, regular-cavity space — interior walls, floor joists that are uniformly spaced, or a garage ceiling. The trade-off: every compressed batt, every gap around a junction box, and every missing fold is a thermal shortcut the batts cannot recover from.
You need insulation and air sealing in one step — around complex attic penetrations, cathedral ceilings, knee walls, or where the existing enclosure has chronic bypasses. Just know that closed-cell spray foam turns the attic into a conditioned space, so soffit venting and HVAC strategy need to be re-thought alongside it.
You need a high R-value in a thin profile — a sloped attic ceiling, a tight knee wall, a garage ceiling below a conditioned room, or the exterior sheathing under new siding. Rigid foam is rarely the whole attic's insulation on its own; it's the right tool for the spots where batts and cellulose physically won't fit well.
Most real attic projects end up using two of these together — cellulose for the open attic floor plus rigid foam on a knee wall, or spray foam on the bypasses plus cellulose over the rest. A Stravix inspector will tell you which combination matches what's actually up there.
A free attic inspection takes about 45 minutes and gives you a real picture of your attic's condition, your current insulation type and R-value, and what (if anything) a Stravix upgrade would look like for your home. No obligation, no pressure — just information.