How to Insulate a Cathedral Ceiling with Blown Insulation

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  • 8-12 hours
  • Intermediate
  • 450-2,000
What You'll Need
Caulking gun
Cellulose insulation
Dust mask
Protective clothing
Hopper and blowing machine for insulation
Drill and hole cutting bit

Considering the height of a cathedral ceiling along with the lack of attic space, insulation becomes an important issue. Given that homes with cathedral ceilings are prone to high energy costs both in the summer and the winter the homeowner should make use of the most effective insulation products and techniques. Of course, it is also wise to pay a visit to your building code office to find out if there are any material or procedure requirements. Another good resource is the Department of Energy for fact sheets and potential tax credit programs relating to insulating your home. This job will also require a helper.

Seal Air Leaks and Install Vent Chutes

Starting at the top of the house, seal around electrical lights, pipes, wires, wall plates, duct connections, and exits where components and vents enter the house. Move to the basement and do the same paying particular attention to plumbing entry points. The primary places will be in the attic and the basement of the house. To prevent blocking soffit vents into the attic, install baffles or vent chutes in each rafter to allow air to pass to the ridge vent.

Calculate the Quantity of Insulation

Measure the height, length, and width of your attic space and multiply the three measurements to determine the cubic feet of insulation. The chart on the bags of insulation will have a reference chart to tell you how many bags you will need. Dense pack cellulose insulation, made primarily of recycled newsprint, is a non-toxic safe, affordable insulation with a stated R-value of about 3.5. Tightly packed cellulose is also effective in impeding air loss through cracks and gaps which are responsible for about one-third of heat loss in homes.

Rent and Assemble Blower

You will likely be renting a hopper and blower. Be sure to get the small 1 to 2-inch diameter fill tube for filling cathedral ceilings.

Drill Holes in Roof

Typically cathedral ceiling insulation is blown in from the roof. In order to do this, you will have to remove pieces of the roofing material and drill a series of 2-inch holes across the structure in each framing cavity.

Blow the Insulation

You will need a helper for this step to keep your hopper full and break up clumps as the insulation feeds through the hose. Insert the hose in the drilled hole and shove it into the enclosed cavity and begin blowing in the insulation. When the blower begins to stall back out the hose bit by bit and continue the process until the cavity is entirely filled. Your helper should be continually filling the hopper as you are blowing the insulation.

Repair Roof

Replace any trim that you have removed, and patch the holes in your roof. Reinstall all roofing materials.