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How To Lay Attic Insulation

by Michael Boyle on June 12, 2019

Up to 35% of your home’s heat can be lost through your ceilings if your attic is not properly insulated, and this costs you hundreds of euro per year. It makes great sense then to make sure you have sufficient insulation material in your attic, to retain your heat.

What you’ll need:

  • Correct amount of insulation material (see Step 1)
  • Scissors/Stanley Knife
  • Suitable clothing and protective equipment – long-sleeved top, dust mask, gloves, goggles, etc.
  • Tape measure
  • Torch
  • Kneeling board to put between ceiling joists

In most homes, where the attic is not used as living space, laying rolls of insulation material is the best way to achieve that. We stock a number of options such as Knauf Earthwool, Knauf Omnifit and Rockwool Rollbatt rolls, but the basic method of laying them is the same.

Step 1 – Get Your Materials

Calculate the size of your attic in m2, and then come talk to us to find out which insulation material is best for you. The number of m2 of insulation material in each pack will be clearly marked, so divide the area of your attic by the amount in each pack, to calculate the number of packs you need. It is generally best to round up to the nearest whole number, although some allowances can be made for areas that are unable to be insulated.

Step 2 – Prepare for Installation

Knauf Earthwool and Knauf Omnifit products are a low dust and low itch products, but it is still advisable to wear suitable clothes and safety equipment – including a long-sleeved shirt and dust mask – and place your rolls of insulation material in your attic. However, do not take them out of the packaging until have the insulation in your attic and you’re ready to actually install them. And just before installation, as you remove it from the packaging, gently agitate the insulation by shaking it or bouncing it on its side, so that it recovers to its full thickness.

Step 3 – Begin Installation

Start installing your insulation at the further corners of your attic, and work back towards your attic access point. As you begin by installing in the eaves (i.e. where the roof joins the ceiling), be careful the insulation does not come in contact with the roof itself – leave a gap of approx 25mm (1 inch).

Step 4 – Work Smoothly

Continue to work your way smoothly and methodically through your attic, unpacking your insulation material one roll at a time. Whether installing between ceiling joists or in a truss roof, ensure a snug fit throughout, avoiding any gaps. Where required, a sharp knife can be used to cut the insulation material to fit.

Tip: Do not squeeze or compress the insulation as this will reduce its insulating ability. i.e. 200mm insulation squeezed down to 150mm will only have the insulating ability of 150mm of Insulation.

Step 5 – Review the Work

Carry out a final check of the insulation, making sure all areas have been covered with an even layer. Don’t forget to also insulate the rear of your attic access panel. Then remove all packaging and excess insulation material from the attic, dispose of it responsibly.

Tip: Do not insulate under your cold water storage tank, as the heat rising at this point will help to prevent the water in the tank from freezing in winter. Invest in a water tank jacket to help reduce the chances of your tank freezing.


Safety measures to be aware of while laying attic insulation material include:

  • Be careful of electrical cables – turn your mains power to ‘OFF’ before starting work, if possible
  • Wear appropriate clothing such as long-sleeved top and rubber-soled shoes, and protective equipment such as dust mask, gloves, and goggles
  • Stand and kneel only on ceiling joists, or on a board you lay across them – never on the space between them
  • Only open packaging as required
  • Avoid all eye contact with dust or fibres, and minimise any skin contact during installation
  • Take extra precautions around electrical equipment in older homes – consult an electrician for expert advice where necessary