Simple tips for installing attic insulation

July 27, 2015

Most homeowners can install insulation in their attics on their own, saving them money. Here's how you can insulate your attic.

Simple tips for installing attic insulation

Make a safe work environment

  • Hang safety lights from the attic ceiling so you can see clearly while you work.
  • If you step into the space between joists on an attic floor, your foot may break through the ceiling of the room below. That can mean an expensive repair, as well as a possible injury.
  • Don't try to crawl around the attic with your knees on top of the joists.
  • Set boards or pieces of plywood perpendicular to the joists to make a working platform, and move them around as you work.
  • Make sure each board end is supported by a joist.
  • Before you get started, make sure you have a solid flat surface for cutting insulation, a high-quality utility knife and a straight piece of wood for a cutting guide.

Get the necessary gear

Because fibreglass is made of bits of spun glass, the fibres can irritate nasal passages and cause skin rashes. Always wear the following equipment to protect yourself:

  • Wear head protection because you may bump your head on the roof joists.
  • Always wear long-sleeved shirts and pants when working with fibreglass, and secure them at the cuffs and legs.
  • Shield your eyes with protective goggles and wear a face mask to prevent inhaling the tiny bits of glass.
  • Note that people with sensitive skin may develop a rash or have trouble breathing even after taking these precautions.

Choose the right insulation

Consider the type of insulation and thickness that's best for your attic. If you plan to make a floor in the attic, so that you can use the area for storage, make sure the insulation will not rise above the top of the joists. Buy insulation of the correct width to fit snugly.

Protect against water vapour

  • On one side of rolled batts of insulation is a vapour retarder, designed to reduce the passage of water vapour into the insulated space.
  • The vapour retarder goes toward the hot side of the surface being insulated (the ceiling of the room below the attic floor, for example).
  • If you're installing insulation on an attic floor where there has been none before, place the vapour retarder down.
  • If you're adding extra insulation to the floor, use unfaced batts. A vapour retarder is already in place below the old insulation.

Lay the insulation correctly

  • Open each roll of insulation by slicing the tape holding it together.
  • Install the batts with the vapour retarder facing down.
  • Start at a corner where the floor meets the roof rafters and roll toward the middle of the room. Don't cover any soffit vents.
  • Take the time to cut your insulation precisely, since heat will be lost wherever there's a gap.
  • Measure with a tape measure and mark the insulation for cutting by giving it a quick, short slice with a utility knife.
  • Position the insulation on a scrap of plywood a bit longer than the batt is wide. Place a piece of wood across the insulation. Then press down to compress it and slice through, using the edge of the wood as a cutting guide.


Fibreglass roll-type or batt-type insulation is the easiest kind to install yourself. You simply roll it out and place it between the joists. Equipment for blowing in loose-fill insulation can be rented. But for most homeowners, this job is best left to a professional.

Installing attic insulation isn't as difficult as it may seem, as long as you work safely and efficiently. If you do, you can have a well-insulated attic for less.

The material on this website is provided for entertainment, informational and educational purposes only and should never act as a substitute to the advice of an applicable professional. Use of this website is subject to our terms of use and privacy policy.
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