How to insulate a loft

Before you start, you’ll need to find out how much insulation your loft has (if any). Your loft might already have some insulation.

Check first that this is in good condition. If it’s very old and/or has become damaged by weather, vermin or has become compressed, it’s best to remove it and start the job with new insulation. But if it’s in good condition you can just add a layer on top.

To find out how much insulation is installed, use a tape measure to:

1. Measure the depth of the insulation
2. Measure the space between the joists: this will tell you what width of insulation roll you need

When it comes to depth, we recommend a minimum insulation depth of 270mm for your loft.

For example: if you have 120mm of loft insulation already installed, you’ll need to top it up by at least 150mm. Or, if you’re starting from 0mm, you’ll need at least 270mm.

For width: the most common width between joists is 400mm or 600mm. You’ll need insulation rolls that will fit into the space between joists. Most rolls are wider than this but are pre-cut, so they can easily be separated into suitably sized strips.