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How to Insulate a Roof Without an Attic

Not every roof insulation job involves an attic space. A cathedral ceiling is the most common example in homes. If you’d like to learn how to insulate a roof without an attic first you’ll need to decide what type of insulation you’d like to utilize. In many ways, insulating the roof will be similar to insulating a wall, except you’re working over your head. You must also be mindful not to block eave vents if they are present. When working with most insulation products, you should wear a mask to avoid breathing in harmful materials. Putting on a protective suit and eye protection is also recommended.

Directions for How to Insulate a Roof Without an Attic

  1. Set up a scaffold or ladder so that you can reach the exposed roof joists.
  2. Measure the length, width, and depth of all areas between the roof joists.
  3. Use the dimensions to calculate how much insulation material to buy.
  4. Decide what kind of insulation that you want to use. Popular and affordable options are fiberglass batts, wool batts, and spray foam.
  5. Check to see if eave vents are present because you must not cover these with insulation.
  6. If eave vents are present, install baffles to the underside of the roof decking between all joists.
  7. Position the baffles end to end and staple them to the roof.
  8. Install baffles all the way up to the ridge vent.

Insulating with fiberglass batts:

  1. After installing baffles if needed, start at the bottom of a ceiling corner.
  2. Position your first batt with the craft paper side facing the interior of the room.
  3. Staple through the paper into the joists about every 8 inches.
  4. Fit the next batt snugly against the end of the first batt and staple into place.
  5. Use an insulation knife to cut pieces to fit as you work.
  6. Follow this procedure when learning how to insulate a roof without an attic until all joist spaces are filled.
  7. Leave space around recessed lighting fixtures that are not rated for contact with insulation.
  8. Cut off about 3 inches of craft paper near any fixtures, chimneys, or flues to prevent fire hazards.

Insulating with wool batts:

  1. Cut wool batts with heavy-duty scissors as you work.
  2. Leave a 50mm gap between the roof and the wool batts as you insert them between the joists.
  3. Staple the wool batts to the joists.
  4. Fit each piece snugly against the preceding piece.
  5. Leave gaps around hot light fixtures, flues, and chimneys.
  6. Spread plastic sheeting over the insulation after all pieces are installed.
  7. Staple plastic barrier to joists.

Insulating with spray foam:

  1. Spray foam insulation products work best if the application surface is about 70 degrees.
  2. Consult the directions on the spray foam insulation product that you bought for precise instructions.
  3. Set up the tank and hose and fit on a nozzle.
  4. Spread drop cloths on the floor or other nearby objects to protect them from drips.
  5. Put on your protective gear.
  6. Spray an even layer between the joists, working back and forth perpendicular to the joists.
  7. Start with a thin layer because the foam expands.
  8. Continue this process until all the surface area between the joists has been sealed with foam.

Tools & Materials

  • Safety goggles
  • Protective suit
  • Gloves
  • Dust mask
  • Measuring tape
  • Insulation knife
  • Heavy-duty scissors
  • Heavy-duty stapler
  • Ladders or scaffolds
  • Ventilation baffles, if needed
  • Insulation

Request Professional Insulation Services From PJ Fitzpatrick

The experts at PJ Fitzpatrick can assess your roof to determine your insulation and ventilation needs. We have been improving homes in Delaware, Maryland, Pennsylvania, and New Jersey for over 40 years. Let us provide recommendations on the best way to insulate your roof. Contact our home improvement company for an insulation estimate today.

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