Wall Insulation

Wall Insulation

Extensive renovations provide an opportunity to install insulation not only in external walls but also internal walls.


Extensive renovations provide an opportunity to install insulation not only in external walls but also internal walls.

Glasswool insulation comes in all sizes to fit the void between the framework and will provide both thermal and acoustic performance. Installing insulation in internal walls will prevent noise from transferring between adjoining rooms to improve the comfort of the home.

There is a range of methods and products to improve acoustic performance in walls, the introduction of insulation into the wall will substantially increase the wall’s acoustic performance. We recommend completely filling the cavity with insulation, selecting a product with the highest density for your cavity will achieve the best results.

Wall insulation is easy to install and can be done as a DIY project. For guidance on installation in New Zealand reference NZS 4246:2006 and our installation instructions before carrying out any work.

Installation Instructions
DIY Installation Video

Installation Instructions

Earthwool® glasswool insulation: Wall insulation

These instructions should be read in conjunction with local standards NZS 4246 and all applicable local, state and federal building regulations. Before you start installing, please make sure you are familiar with our safety instructions and precautions. Ensure that you use tools and equipment that are suitable for the intended application. This will include suitable safety equipment.

Do not start work until the site is safe!

Assess the wall 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: NZS 4246:2006.


  • Sharp knife for trimming insulation

  • Ladder

  • Suitable clothing (see our safety instructions and precautions)

  • Tape measure.


  • Determine the most suitable product for your project. Walls can be insulated using rolls or batts.

  • Insulation is available in varying widths and thicknesses to suit most framing spaces. Please check Knauf Insulation’s product guide for the most suitable product for your application.

  • To calculate the number of packs needed, determine the area (m²) to be insulated by multiplying the length by the width or wall height. 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.


  • Don’t take the insulation out of the packages until you’re in position and ready to install.

  • Before installation check that the product selected matches the specification.

  • Ensure that the insulation has lofted to the nominal thickness, if required, gently agitate the insulation by ‘bouncing’ it on its side until it recovers to thickness stated on the label.

  • Where installing around wall lights or heat sources consult the appliance manufacturer’s instructions for appropriate clearances. Additional guidance is provided in NZS4246.


  • When installing insulation between framing members, ensure that you achieve a snug fit avoiding any gaps, tucks and folds.

  • It is recommended that you select products that have the same thickness as the cavity. In circumstances where the cavity is deeper than the product selected, adequate support must be provided.

  • Make sure insulation fits snugly against top and bottom wall plates. The front face of the batt should be flush with the inside face of the framing.

  • For metal frame walls, install insulation according to the relevant Building Code. Friction fit one side of the batt into the metal C-channel and butt the other edge against the metal stud.

  • Install insulation to cover the full height of the wall including spandrel areas.

  • Use off cuts to insulate small and hard to fit areas.


  • Attention to detail is very important. Make sure all areas are insulated, behind electrical outlets, plumbing and services.

  • Seal all penetrations in exterior walls with insulation or foam sealants.


  • Complete a final check of the installation ensuring all areas have been insulated and that you have an even and consistent layer of insulation.

  • Finish your project by removing all packaging and disposing of all rubbish and excess insulation responsibly.

For more installation advice watch our wall install video and read our electrical safety information before doing any work in the walls.