My house already has some ceiling insulation which looks quite old. Can I place new insulation over the top?

The simple answer is Yes. The existing insulation does have some thermal performance (even though it may be low) so it is best practice to ‘top-up’ the existing by adding new insulation on top of it.

There are some reasons you may want to consider removing existing insulation first:

  • If it has been damaged by vermin,
  • It has been covered in rats droppings,
  • Birds have made nests in it,
  • Or if it is wet.

If the existing insulation is wet it can lead to mould, mildew and sometimes the rotting of ceilings or roof rafters. Find the source of the water, such as roof leaks or leaking pipes/header tanks, and fix it. Wet insulation should be removed before any fresh insulation is installed.


Although insulation professionals such as Enstall will handle the installation for you, here are some things you should keep in mind:

  • Segment or blanket insulation can be installed over existing insulation.
  • If using a blanket, the existing insulation should be at least the same height as the joists/truss chords.
  • In this instance, installing perpendicular to and on top of the timbers creates an excellent thermal envelope, minimising thermal bridges.
  • If the existing insulation is below the level of the timber, segment insulation should be installed between the timbers.
  • Alternatively, the best solution may be blow-in loose-fill glasswool insulation.

Blow-in insulation ensures that weak points are minimised by filling gaps in the existing insulation. It gets into all the nooks and crannies and covers all the timber joists. This results in a cosy thermal envelope.

The most important thing to keep in mind is that you don’t have to worry about all this. Our team can answer any questions you have about upgrading your ceiling insulation, and handle your entire home insulation project!


The team at Enstall