Cost-benefit of insulation measures


It’s getting to that time of year when we start thinking of draught-proofing and insulating our homes against the onslaught of winter. There are a host of measures that can be implemented, from small cheap and easy DIY measures, to work that involves more expensive upheaval. But the more you pay, the more you expect to save off your heating bill, right?

Not necessarily!

We had a look at the range of measures recommended by the Energy Savings Trust, and worked out what the payback and cost-benefit was – and the results were surprising:

Payback and cost-benefit of insulation measures

Measure Cost to fit Cost saving per year Payback time
Hot water tank lagging £15 £130 1.5 months
Chimney draught exclusion £30
(Chimney Sheep)
(Chimney Sheep)
6 months
Loft insulation
(where there hasn’t been any at all)
£340 £180 23 months
Pipe lagging £20 £10 24 months
Cavity wall insulation £465 £150 37 months
Suspended timber floor insulation £525 £60 105 months
Loft insulation top up £275 £20 165 months
Internal wall insulation £8,750 £245 429 months
External wall insulation £15,000 £245 735 months
Double glazing £11,420
(The Eco Experts)
£80 1713 months

All data is taken from the Energy Savings Trust website except where stated otherwise. Figures are averaged over the various house types given.

Hot water tank lagging

If you haven’t got your tank lagged then tut tut! These are easy to buy and easy to fit. Like putting a cardigan on a baby. Hot water tank jackets are available in most DIY shops. You can also get more environmentally-friendly ones filled with sheep wool, from

Chimney draught excluder

Most of us are unaware of how much warm air is lost up chimneys. This is mostly because we can’t see or feel it, but we certainly notice the cold draughts from air pulled in to replace the warm air travelling up the chimney. The EST recommends various draught-proofing measures but it is difficult to find data on how much these save you. Chimney Sheep Ltd have had the product tested by BSRIA to determine their cost savings.

Virgin loft insulation

You definitely should have this! Up to 25% of heat loss can be through un-insulated lofts.

Pipe lagging

Unless you regard the exposed pipes as a way of heating your home before it reaches the radiators / taps, then get your pipes lagged. It’s so easy it’s almost fun, and so cheap you hardly need worry about the payback, but well worth it nonetheless.

Cavity wall insulation

One of the “bigger” measures, that is the cheapest and easiest to do.

Suspended timber floor insulation

Up to 15% of household heat is lost through the floor and although it would take nearly nine years to recoup the cost, it will make your home more comfortable.

Loft insulation top-up

Although it’s not going to save nearly as much as putting insulation into a loft that has never been insulated before, it’s still going to make your home a lot cosier for a relatively low out-lay.

Internal wall insulation (wall lining)

This is getting expensive. Don’t think about payback, just think about how much cosier your home is going to feel. Up to 35% of household heat is lost through uninsulated walls.

External wall insulation (over-cladding)

As internal wall insulation.

Double glazing

I don’t think we should think about fitting double glazing as a money-off-your-bill exercise. The maths doesn’t add up. It was hard to get figures for what it would cost to fit double glazing to the average home. The EST had figures for how much it could save, but no estimates for fitting it (which they did for the other products, except for draught excluders). Double glazing will save you some money off your bills, but never pay for itself. They will make your home more comfortable, reduce draughts, and look nice if you get the right sort.