Insulation Savings Calculator

Why Insulation Saves More Than Anything Else

A heat pump, smart thermostat, or solar panels are all great, but none of them matter if your heat is escaping through the roof, walls, and gaps around the doors. Insulation is the foundation of an energy-efficient home. Every other upgrade works better when the building envelope is properly sealed.

The Energy Saving Trust estimates that an uninsulated home loses:

• 25% of heat through the roof: loft insulation fixes this
• 35% through the walls: cavity or solid wall insulation
• 15% through the floor: floor insulation or just sealing gaps
• 10% through windows: double glazing or window film
• 15% through draughts: draught proofing doors, chimneys, letterboxes

The calculator above shows you which measures will save the most for your house type, and how quickly each one pays for itself.

The Cheap Wins Most People Miss

Before spending thousands on cavity wall insulation or glazing, check these first:

Pipe and hot water cylinder insulation (under £80)

If you can see unlagged pipes in your loft or airing cupboard, you're literally watching money evaporate. Foam pipe lagging costs £4–£7 per metre and takes 5 minutes to fit. Just push it over the pipe. A hot water cylinder jacket (£25–£30) saves £25–£50 per year. These are the best payback of any home improvement.

Loft hatch insulation (under £25)

Your loft hatch is almost certainly uninsulated and poorly sealed. It's like having a small hole in your ceiling. A foldable insulation cover (£23) sits on top of the hatch and takes 5 minutes to fit. Read our loft insulation guide for the full DIY walkthrough.

Draught proofing (£100–£300)

Run your hand around your front door on a cold day. Feel that? A door seal costs £25, a chimney sheep costs £33, and a letterbox excluder costs £14. The whole house can be done in an afternoon for under £100, saving £50–£120 per year.

The Big Ticket Measures

Loft insulation (£300–£1,000)

If your loft has less than 270mm of insulation (check with a ruler), topping it up is the single best-value professional measure. Many households qualify for free loft insulation through ECO4 or GBIS. Check our grant eligibility checker before paying.

Cavity wall insulation (£800–£2,500)

If your home was built between the 1930s and 1990s, you probably have cavity walls. A professional injects insulation into the gap: it takes a day, is minimally disruptive, and saves £250–£500 per year. Again, ECO4/GBIS may cover the full cost. Read our cavity wall insulation guide.

Double glazing (£3,000–£12,000)

The most expensive measure and the slowest payback. If you have single glazing, it's worth doing, but window insulation film (£13) is a much cheaper interim solution that gives you 60–70% of the benefit.

Grants That Can Cover the Cost

Two main schemes fund insulation in the UK:

• ECO4: fully funds insulation for qualifying households (low income, EPC D or below). Covers loft, cavity wall, floor, and solid wall insulation.
• Great British Insulation Scheme (GBIS): covers insulation for homes in council tax bands A–D (England) or A–E (Scotland/Wales). Not means-tested. You just need to be in the right council tax band.

Check your eligibility with our grant checker before spending anything. Many households are eligible and don't realise it.

The Order That Matters

If you're doing multiple measures, the order matters. This is the sequence most energy assessors recommend:

1. Draught proofing: cheapest, fastest payback, DIY
2. Pipe and cylinder insulation: cheap, fast payback, DIY
3. Loft insulation: high impact, often free via grants
4. Cavity wall insulation: highest saving, needs professional, often grant-funded
5. Floor insulation: moderate saving, more disruptive
6. Glazing: expensive, slow payback, do last

For the full picture, see our home insulation costs guide or use our EPC improvement calculator to see how each measure affects your energy rating.