Energy & efficiency
Insulation: start where the heat leaves
Heat rises, and in most houses it keeps going: up through a thin loft, out through gappy floors, sideways through unfilled walls. Insulation pays best when you follow the heat. So this is the order: loft first, the forgotten details second, walls last and with your eyes open.
By the Tickover team · Published 29 April 2026 · 5 min read
Loft first, always
The target is 270mm of mineral wool, and plenty of homes are still sitting on the 100mm that counted as generous decades ago. Topping up is the king of paybacks: cheap materials, an afternoon of unglamorous work, and a saving that often clears the cost within one to three winters. A careful DIYer can do it; so can an installer for not much more.
At the time of writing, energy-saving materials carry 0% VAT, which keeps the rolls cheap whoever lays them. About a quarter of an uninsulated home’s heat leaves through the roof, so this is the leak to plug before any grander plans.
Topping up the loft, properly
Check what is up there first
Measure the current depth with a tape and look for damp stains on the felt; fix any leak before burying it. If an older loft holds loose granular fill rather than wool, have it identified before disturbing it, as some old loose fills contain asbestos.
Keep the eaves breathing
Do not stuff wool into the eaves. The airflow there dries the roof timbers; use vent trays if the gap is tight.
Fill between the joists
First layer sits level with the joist tops, tucked in without cramming.
Cross-lay the second layer
Run it at right angles over the joists up to 270mm. Never compress it; squashed insulation stops insulating.
Mind cables and downlights
Clip cables above the wool where you can, and give recessed downlights proper covers with clearance rather than a blanket.
Dress the pipes and the hatch
The loft is colder now. Lag every pipe, jacket any tank, then insulate and draught-strip the hatch itself.
The details that punch above their weight
An uninsulated hatch is a hole in the middle of your new blanket, which is why it gets its own step above. Pipe lagging matters for the same reason: pipes that used to sit in escaping warmth now live in cold air, and a frozen, burst pipe refunds years of savings in one soggy evening.
Downstairs, suspended timber floors leak air at every skirting gap. A tube of sealant along the junctions, draught excluders on the doors, and rugs, which remain legitimate technology, sort the worst of it. Leave the airbricks in the outside walls clear though: the void under the floor needs its ventilation, or the joists pay for it.
Walls: the reality check
Homes built from roughly the 1930s onwards usually have cavity walls. If yours are unfilled, filling them is the next best value: £1,000–£3,000 as a guide, done in a day by a registered installer who should assess suitability first and leave you a guarantee. That suitability check is not a formality; exposed, rain-battered walls can suffer damp if the wrong cavity gets filled.
Solid walls, standard in older homes, are a different league: insulating them means internal or external works costing several times a cavity fill, with design decisions attached. Get two or three quotes and independent advice before committing. For most households the honest sequence is loft, details, cavity, and only then the solid-wall question, exactly as the bill-cutting order has it.
| Measure | Typical cost | Payback |
|---|---|---|
| Loft top-up to 270mm | £150–£600 as a guide | Often 1–3 years |
| Hatch and draught-proofing | Under £100 DIY | A winter or two |
| Floor gap sealing | A few tubes of sealant | Quick, plus comfort |
| Cavity wall fill | £1,000–£3,000 as a guide | A few years |
| Solid wall insulation | Several times cavity fill | Long haul; get 2–3 quotes |
The two headline jobs
Loft top-up to 270mm
DIY materials through to installed
Cavity wall insulation
Registered installer, with guarantee
Typical UK ranges, mid-2026, as a guide only. Your home, your area and the job itself all move the number — always compare real quotes.
~25%
of heat escapes through an uninsulated roof
270mm
the loft depth to aim for
0%
VAT on insulation at the time of writing
What insulation sets up next
Insulation is also the gateway drug to everything else on the energy list. A well-insulated home needs a smaller, cheaper heat pump, which is why the readiness check starts in the loft, and the same measures are among the most reliable ways to lift an EPC rating before a sale or a let. Do the boring layer first and every later project shrinks.
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Quick answers
How thick should loft insulation be?
The standard to aim for is 270mm of mineral wool. Many homes have 100mm or so from an earlier era, which is why a top-up layer laid at right angles over the joists is the usual job. Depth only works if it stays fluffy: compressing insulation under boards or boxes undoes it, so boarded storage needs raised legs.
Can I insulate my loft myself?
Usually, yes. It is an afternoon of dusty, itchy work: gloves, a mask, long sleeves and boards to kneel on. The judgement calls are keeping the eaves clear so the roof can breathe, covering downlights properly, and lagging pipes afterwards. Pause and get advice if you find damp, wildlife, or an old loose-fill material you cannot identify.
Is cavity wall insulation a good idea?
Where the wall suits it, yes: it is a one-day job costing £1,000–£3,000 as a guide, with a payback measured in a few years. The caveat is suitability. Exposed walls that take heavy driving rain can develop damp problems if filled, so use a registered installer who assesses the wall properly and backs the work with a guarantee.
Will insulating my house cause condensation?
It can, if ventilation gets sealed along with the heat. A tighter house holds more moisture from cooking, washing and breathing, and that moisture condenses on the coldest surfaces left. Keep trickle vents open, run extractor fans, dry clothes with airflow, and treat misty windows or corner mould as an early warning rather than a mystery.
This guide is general information for UK homes, not advice about your specific property. Anything involving gas must be done by a Gas Safe registered engineer, and notifiable electrical work by a qualified electrician. If you smell gas, call the National Gas Emergency line on 0800 111 999. If you’re ever unsure, stop and get a professional in — that’s exactly what Tickover is for.
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