Attic Insulation in Southfield, MI

Loose-fill fiberglass is blown through a hose from a machine in the truck. It fills around wiring, bracing and odd-shaped bays that batts leave gaps around. HomeGuide puts blown-in insulation at $0.90 to $2.40 per square foot, depending on the attic size, the target R-value, and how much damming and air sealing the job needs. It's the usual choice for topping up an existing attic floor. The installer should staple depth rulers to the joists so you can see the finished depth from the hatch.

Cellulose is a paper-based loose fill, blown the same way as fiberglass and priced in the same blown-in range. The bag label gives the depth needed for each R-value, and the installer should blow to that depth, not eyeball it. Fiberglass and cellulose both work. What matters more is that the attic floor is sealed first and the depth hits the target everywhere, including out at the eaves.

Spray foam on the underside of the roof deck moves the insulation from the attic floor to the roof itself. The attic then becomes part of the heated space, and the soffit and ridge vents are closed off. That suits an attic full of ductwork or a finished half-storey. Foaming the rafters and roof deck runs $1,500 to $9,000. It's a different design, not a stronger version of the vented attic, so it needs to be planned with the roofer, not added on its own.

Insulation slows heat. It doesn't stop air. ENERGY STAR's air sealing guide lists where warm house air gets into the attic: behind and under kneewalls, the attic hatch, wiring and plumbing holes, dropped soffits open to the attic, recessed lights, and the furnace flue or duct chase, where a metal dam keeps insulation away from the hot pipe. EPA recommends sealing before insulating, because once ten inches of fluff is on top, nobody finds those holes again. Air sealing an attic runs $350 to $3,000.

Most attics get topped up, not stripped. Removal makes sense when the old insulation is wet from a roof leak, contaminated by animals, or packed so thin that air sealing can't happen underneath it. Removal costs $1 to $2 per square foot. One material is a special case: vermiculite, the gray-brown pebbly fill found in some older attics. EPA says to assume it contains asbestos and not disturb it. Removal is a job for a professional asbestos contractor, not an insulation crew with a vacuum.

Baffles, also called rafter vents, are foam or cardboard chutes stapled between the rafters at the eaves. They hold an open path from the soffit vents into the attic, so new insulation can go all the way out to the wall without blocking airflow. Burying a soffit vent is the one mistake ENERGY STAR puts in capital letters, and the model residential code (IRC R806.3) wants a clear inch or more above the insulation where the vents are. Baffles cost $2 to $3 each, among the cheapest parts of the job, and they matter for the roof ventilation above.