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Loft insulation FAQs

Get answers to frequently asked questions with our loft insulation FAQs

How much heat escapes through the roof

On average, about 25% of household heat escapes through an uninsulated roof.

How much loft insulation should I use?
Felt Lap Adhesive

Building Regulations recommend a minimum of 270mm thickness, comprising of a 100mm bottom layer between ceiling joists and a 170mm top-up layer above. This should be laid at a 90º angle to the bottom layer to ensure coverage of the timber ceiling joists.

Should I replace existing loft insulation?

If well-fitted and in good condition, there is no need to replace your insulation. You can simply lay new insulation on top of it to reach the recommended 270mm thickness.

Do I need to maintain ventilation at the eaves?
Felt Lap Adhesive

You must ensure a 25mm air space is maintained at the eaves between the loft insulation and the roofing underlay. If you block ventilation to your loft space you may get problems with condensation.

Should I insulate my water tank and pipework

Yes, but don’t use loft insulation. Specific tank and pipe insulation will prevent them from freezing in the cold months of the year.