- Loft insulation and draught-proofing pay back fastest by a wide margin.
- Expensive measures can take decades to repay — do the maths first.
- Grants exist and go widely unclaimed, particularly for low-income households.
Insulation is sold as an obvious win, but the payback varies enormously. Some measures repay themselves within a couple of years. Others take longer than most people stay in a house. The difference is worth understanding before you spend anything.
Start with the cheap wins
Draught-proofing
The cheapest measure available and usually the fastest payback. Materials cost very little, the work is a weekend job, and the effect is immediate. Seal around doors, windows, letterboxes, keyholes, floorboards and unused chimneys.
Do not seal air bricks, underfloor vents or extractor outlets. Those are deliberate, and blocking them causes damp and, with fuel-burning appliances, a genuine safety risk.
Loft insulation
If your loft has little or no insulation, this is the single highest-value upgrade in most homes. Heat rises, and an uninsulated loft loses a great deal of it. The recommended depth is around 270mm — many older homes have far less.
Topping up from a shallow existing layer is cheaper and still worthwhile, though the gain is smaller than going from nothing. It is a DIY job for a straightforward loft, but do not compress the material and do not block eaves ventilation.
Hot water cylinder jacket
If you have an older uninsulated cylinder, a jacket costs very little and pays for itself quickly. Also insulate the exposed pipework between the boiler and cylinder.
Reflective radiator panels
Cheap, and worth doing on radiators fixed to external walls in solid-wall homes. The benefit is modest but the cost is tiny.
The middle tier
Cavity wall insulation
If your home was built with a cavity between the outer and inner walls — broadly, most UK homes built from the 1930s onwards — and it has not been filled, this is usually a strong payback.
Two cautions. First, check whether it has already been done; a lot of homes were filled decades ago. Second, in a small number of exposed, wind-driven-rain locations, cavity fill has caused damp problems. Use an installer registered with a recognised guarantee scheme, and make sure the property is assessed as suitable first.
Floor insulation
Worth it for suspended timber floors with a void beneath, which are common in pre-war homes. Disruptive but effective. For solid concrete floors it is rarely economic unless you are already replacing the floor.
Double or secondary glazing
Replacing single glazing with double is a real improvement in comfort and noise, but the payback on energy alone is long. Secondary glazing — a second internal pane — is far cheaper and often the sensible choice, especially in listed buildings or conservation areas where replacement is restricted.
Replacing functioning double glazing with triple is almost never justified on energy savings alone.
The expensive tier
Solid wall insulation
Homes built before roughly 1920 usually have solid walls with no cavity. Insulating them — internally or externally — makes a large difference to heat loss, but it is expensive and disruptive.
Internal insulation reduces room size and means redecorating. External insulation changes the appearance of the building and may need planning permission. Both need doing properly: badly specified solid wall insulation can trap moisture and cause serious damp, particularly in older buildings that were designed to breathe.
Get advice specific to your property’s construction. This is not a DIY job and not one to buy from a cold call.
Do the payback sum
Before any measure, work out roughly: annual saving, divided into the cost, gives the years to break even. Then ask honestly how long you expect to live there.
Draught-proofing might repay in a year or two. Loft insulation from scratch, a few years. Solid wall insulation can take decades on energy savings alone — which does not make it wrong, but it means comfort, damp control and property value have to be part of the reason.
Check for grants before you pay
Schemes change frequently and vary between England, Scotland, Wales and Northern Ireland, but support is generally available for households on certain benefits, in low-income areas, or in properties with poor energy ratings.
Check GOV.UK, your local council, and your energy supplier — suppliers have obligations to fund efficiency measures and do not always advertise them prominently. A great deal of this funding goes unclaimed.
Be cautious of unsolicited calls and doorstep offers of “free” insulation. Genuine schemes exist, but so do poor installations sold hard. Verify the scheme independently before agreeing to anything.
Order of work
- Draught-proof.
- Insulate the loft and hot water cylinder.
- Fill cavity walls if suitable and not already done.
- Check eligibility for grants before considering anything expensive.
- Only then look at glazing, floors or solid walls.
