Loft insulation is one of the simplest and most cost-effective ways to reduce heat loss in a UK property. The Energy Saving Trust estimates that a properly insulated loft can save up to £150 per year on energy bills — and installation is well within DIY capability.
Choosing the Right Loft Insulation Roll
The two most common materials for loft insulation rolls are:
- Rockwool (mineral wool) — non-combustible, excellent thermal and acoustic performance, easy to cut and fit, recommended for most UK lofts
- Knauf Earthwool — glass mineral wool, lighter weight, good thermal performance, slightly easier to handle
Both are available in rolls sized to fit standard UK joist spacings (400mm and 600mm centres).
How Much Insulation Do You Need?
UK Building Regulations and the Energy Saving Trust recommend a total depth of 270mm for loft insulation:
- 100mm between the joists (first layer)
- 170mm across the joists at 90° (second layer)
If you already have some insulation, top it up to reach 270mm total.
Step-by-Step Installation
- Clear the loft and check for any roof leaks or damp before starting
- Ensure the loft is ventilated — do not block eaves
- Lay the first layer between the joists, pushing it to the eaves but leaving a 25mm ventilation gap
- Lay the second layer across the joists at 90° to the first
- Cut rolls with a sharp knife or scissors — compress slightly to fit tight spaces
- Do not insulate under the cold water tank — it needs warmth from below to prevent freezing
Protecting Loft Pipes
This is the step most DIYers miss. Once you insulate the loft floor, the space above becomes significantly colder — any pipes running above the insulation level are now at serious risk of freezing.
Before completing your loft insulation:
- Insulate all water pipes in the loft with pipe lagging — minimum 25mm wall thickness for frost protection
- Insulate the cold water tank on the sides and top (not the bottom)
- Use Armaflex self-seal pipe insulation for easy installation in tight loft spaces
Building Regulations
Loft insulation in existing dwellings is covered by Part L of the Building Regulations. For most domestic properties, 270mm mineral wool meets the required U-value of 0.16 W/m²K.
New builds and extensions may have stricter requirements — check with your local authority or building control.
Products We Recommend
- Rockwool Roll loft insulation
- Armaflex Self-Seal Pipe Insulation for loft pipes
- Armaflex Pipe Insulation for cold water tanks
Shop the full range at pipelagging.com
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