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Roof vs ceiling insulation—what’s the difference?

You might be surprised to find out, there are big differences between roof insulation and ceiling insulation. Ceiling insulation sits on top of your ceiling plasterboard whereas roof insulation (also known as roofing blanket) sits directly against the underside of your metal roof.

While ceiling insulation is a simple job for a DIY-er’s new or existing build, roof insulation can only be installed during the construction of a new roof. Due to this, we recommend reaching out to a trusted roofing company for installation of your roof insulation. There are a number of great roofers we work with and recommend in Queensland, New South Wales and the ACT. Please feel free to contact us directly for a list of companies.

Read on for DIY ceiling insulation instructions.

DIY ceiling insulation INSTRUCTIONS

Written DIY Instructions


  • Determine the most suitable product for your project. Ceilings can be insulated using rolls or batts. Insulation is available in varying widths and thicknesses to suit most framing spaces. Determine the most suitable product for your project.
  • Where you have existing insulation that is level with the ceiling joists, you can install additional insulation over the top. It is recommended that this is installed at right angles to the existing insulation.
  • To calculate the number of packs needed, determine the area (m2 ) to be insulated by multiplying the length by the width. The number of m2 of insulation material is clearly marked on each pack. Divide the total area to be insulated by the m2 in a pack to determine the number of packs required (don’t forget to round up to the nearest whole pack). Allowances should be made for areas that are unable to be insulated. You can also use the Ecolife Solutions online insulation calculator.


  • Don’t take the insulation out of the packaging until you’re in a position and ready to install.
  • Before installation, gently agitate the insulation by gently shaking or bouncing it on its side until it recovers to the thickness stated on the label.
  • Do not block ceiling vents and take care around downlights and other sources of heat. Consult the manufacturer’s instructions for appropriate clearances. Additional guidance is provided in AS 3999 and NZS 4246.


  • Start installing the insulation at the far corners of the ceiling and work your way back towards the ceiling access.
  • When installing insulation between ceiling joists, ensure that you achieve a snug fit avoiding any gaps.
  • When installing insulation in truss roofs, ensure that insulation is firmly butted together to achieve a consistent layer of insulation without any gaps.
  • Where required, use a sharp knife to cut the insulation to fit. It is important that when you cut the insulation that you avoid coming into contact with any electrical services.
  • When installing insulation in a roof eave (i.e. where the roof joins the ceiling), make sure the insulation covers the top plate but is not in contact with the roof. It is important to maintain a 20mm gap between the roofing substrate and the insulation.


  • Complete the final check of the insulation ensuring all areas have been insulated and that you have an even and consistent layer of insulation.
  • Finish your project by removing all packaging from the ceiling and disposing of all rubbish and excess insulation responsibly.


  • Once you have worked your way back to the ceiling access, make sure you insulate the ceiling access panel before exiting the roof space. We recommend that once completed another person checks the work to ensure it has been installed according to required standards.


Install Tips

  • Work with another person and maintain contact throughout both the assessment and installation process
  • Complete a pre-work assessment before installation to identify safety hazards
  • Install insulation during the coolest part of the day
  • Drink plenty of water
  • Wear appropriate clothing for the job

Tools Required

  • Sharp knife for trimming insulation
  • Ladder
  • Suitable clothing (see our Health and Safety Information)
  • Tape measure
  • Non-conductive insulation stick for positioning insulation in hard to reach areas
  • Kneeling board to span ceiling framing

MUST READ: Do not start work until the site is safe!

Assess the ceiling condition and structure together with the method of installation you are to use based on the appropriate requirements established in the building code, site assessment and or plans provided. Installation must be completed to the requirements of relevant standard: AS 3999:1992 or NZS 4246:2006.

Important DIY Note:
These instructions should be read in conjunction with local standards AS 3999 or NZS 4246 and all applicable local, state and federal building regulations. Before you start installing, please make sure you are familiar with the Earthwool® Health and Safety Information. Ensure that you use tools and equipment that are suitable for the intended application. This will include suitable safety equipment.


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