Attic Air Sealing & Blown-In in Prosper, TX

Attic air sealing and blown-in insulation is the lower-cost way to fix a hot attic, and in many Prosper homes it is the right call. The idea is simple: keep the attic vented, but make the ceiling below it airtight and bury it under a deep, even layer of insulation. It works best when the ducts are short or mostly below the ceiling, but even in houses with equipment upstairs, sealing the attic floor and the duct boots makes a noticeable difference for less money than foam on the roof deck.

The leaks that matter in new homes

In two-story homes built in the last couple of decades, the worst leaks are usually:

• Kneewalls around bonus rooms and second-floor rooms, where batts have no backing and attic air moves right behind the drywall.
• Chases for flues, plumbing and ducts, left open to the attic.
• Duct boots where supply registers meet the ceiling, often unsealed.
• Recessed lights, bath fans and attic hatches or pull-down stairs.
• Top plates of interior walls, drilled for wiring and plumbing.

We seal each one with foam, caulk, rigid board or fire-rated material as the spot calls for. HomeGuide lists air sealing at $350 to $3,000.

Getting the depth right

Builder-installed blown-in is often uneven: deep in the middle, thin at the eaves, crushed around the air handler platform and along the walkways trades used. We measure in several spots and blow to the target depth everywhere. The 2015 Texas code lists R-38 for Zone 3 ceilings and the 2021 IECC, which Prosper adopted for permits from May 1, 2023, lists R-49. For an existing attic, ENERGY STAR recommends R-49 when starting from nothing and R-38 when topping up three to four inches. HomeGuide's attic guide puts blown-in at $0.90 to $2.40 per square foot.

Cellulose or fiberglass

Both work. Cellulose is denser and resists air movement a bit better; fiberglass is lighter, does not absorb water and settles less. Fixr lists blown fiberglass at $1.65 to $2.60 per square foot and cellulose at $1.75 to $3.80. The quote names the product and the depth needed for its R-value, and we leave rulers in the attic so you can check.

Things we keep clear

Insulation stays back from flues and other heat sources by the required clearance, eave baffles keep the soffit vents open, and service paths to the air handlers and water heaters stay usable. If we find disconnected ducts or bath fans venting into the attic, they go on the list.

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