- Insulation Guide

DIY Instructions: Insulating a Loft

DIY difficulty: Medium

Insulating your loft has two key benefits: you will pay less on your heating bill, and you will have a smaller carbon footprint.  The average household installing insulation will save more than £200 per year on their heating bill, and will reduce their annual carbon footprint by around one tonne.

As with all DIY, preparation is key. Loft insulation is simple to install as long as you prepare well and have the right tools available.

  • Your loft must be accessible with adequate ventilation. If your loft is difficult to access, you'll need to call in a professional to install blown insulation.
  • When buying insulation, make sure you have enough to cover the whole area of your loft with two layers. With mineral wool (the most common form of insulation) the total thickness of the two layers should be at least 270mm.
  • Wear protective clothing including DIY gloves and a mask. The mask is essential as it stops you from inhaling insulation fibres. Gloves and protective clothing prevent skin irritation.
  • You need secure moveable supports to enable you to move safely around your loft. These are vital as the main difficulty with installing loft insulation is the risk of falling through the ceiling.
  • You also need good light. If possible, turn off the mains electricity in your house whilst installing insulation and use a bright battery powered lamp.
  • Examine your loft for mould and mildew. If the loft is damp, the cause of the damp must be dealt with before you install insulation. Check for pests such as wasps and mice. Again, these need to be dealt with before you install insulation.
  • For each step, start in the corner of your loft furthest from the loft hatch, and work backwards toward the hatch.
  • Roll out the insulation blankets between the joists on the loft floor. The blankets should fit snugly between the joists.  If there are any large lumps or swirls in the insulation, carefully smooth them out.
  • Roll out a second layer of insulation at right angles to the loft joists.
  • Don't insulate underneath a cold water tank or pipe work as this could cause them to freeze in cold weather.
  • Don't put insulation near electric wires or lighting as this is a fire hazard.
To comply with UK building regulations and Energy Saving Trust recommendations, the two layers of mineral wool insulation should make up a total thickness of 270mm.  For natural wool, the thickness you'll need varies depending on the product, although you'll usually need less than mineral wool. Thermafleece insulation, for example, should be installed to 250mm thickness.