Looking to add loft insulation? Our guide outlines how much you can expect to pay

Installing the right amount of loft insulation will stem heat loss, saving on energy bills. But just how much does it cost to insulate a loft? Our expert reveals all.

Large numbers of homes in Britain are worryingly underendowed in the insulation department. Peek into a typical roof space and you’ll most likely be greeted by emaciated remnants of old loft quilt interspersed with random bald patches. The reason this matters is because the heat in our homes naturally rises to the top of the house so anything less than a full complement of loft insulation swiftly translates into sky-high energy bills. 

Where properties are suffering from pronounced thinning up top, insulating the loft is the single most effective thing you can do to stem heat loss, and is relatively inexpensive to carry out. But how much does it cost to insulate a loft? Not all lofts are plain sailing, and the sheer variety of insulation products on the market making competing claims can be a trifle puzzling. We look at the options… 

roll of loft insulation in roof of a houseCredit: Shutterstock / gcpics

How much does it cost to insulate a loft?

It depends how much you need and the type you want to install

The recommended depth of standard loft quilt applied above top floor ceilings is 270mm (about 10in). How much loft insulation will cost will depend on the type you want to use and how much of it you need. Here are the main options…

Mineral wool or glass fibre wool insulation
DIY stores typically sell rolls of mineral wool or glass fibre wool insulation in thicknesses of 100mm or 200mm (4in or 8in). These are usually the cheapest type of insulation and are designed to simply be unfurled over the loft floor. A standard 100mm (4in) thick roll of mineral wool thats 9.72m x 1.140m (31.7ft x 3.7ft) costs about £2.25 per sq m.

Assuming you need to top up your existing insulation by 200mm (8in), youd be looking at £5 per sq m, so in total roughly £200 for an average loft of about 40 sq m.


Wear protective clothing 

Standard loft quilts, while very effective and straightforward to apply, can irritate the skin. So when fitting them, it’s advisable to wear protective PPE. Some materials are supplied pre-sealed in polythene to mitigate this issue – but if they need to be cut, it’s still an issue.

Polyester loft roll insulation
Another popular type of loft roll is polyester made from recycled plastic bottles, which is softer and claims to be non-itchy.

Natural insulation
Natural materials such as sheep’s wool are much nicer to work with but are more expensive, costing around £17 per sq m for 100mm (4in) depth, and need to be applied to a greater thickness to get the same level of insulation, say about 300mm (12in) depth.  

Unless your loft has a lot of awkward spaces, it’s normally advisable to stick to one of these quilt products sold in rolls, particularly as they readily lend themselves to DIY installation.

Cellulose fibre insulation
Cellulose fibre insulation is an interesting alternative material (made from treated recycled newspapers) that’s professionally installed using blowers to achieve consistent depth of coverage.
Thermofloc Loose Fill Cellulose Insulation costs around £29 for 12kg (26.5lb). The manufacturer recommends 4kg (8.8lb) per sq m per 100mm (4in) depth. 

Reflective insulated foil
Sheets of reflective insulated foil, such as
SuperFOIL SF19+ Multifoil Insulation – around £120 for a 1.2m x 10m (3.9ft x 32.8ft) roll – are another option but are generally better suited to new builds or for insulating at rafter level, which is a more complex operation.  

When ordering insulation materials, you need to allow at least 10% for wastage. 

large slab of mineral wool loft insulationCredit: Shutterstock / Arturs Budkevics

How much does it cost to have loft insulation installed?

Tradespeople will charge around £250 per day

If the idea of boldly shimming up loft ladders on a DIY mission isn’t your cup of tea, then employing tradespeople to do it for you will likely set you back around £250 per day in labour rates. This is a consistent figure regardless of the type of insulation used. Add this onto how much your chosen loft insulation costs.

Unfurling rolls of loft quilt is a straightforward job and can be done relatively quickly. For a typical rectangular roof space with decent headroom, it may only take a couple of hours. But you’ll need to factor in at least the same amount of time for preparing access. Most lofts are home to piles of belongings that need to be cleared out of the way. Then there’s the pipework and lengths of electric cable that need to be negotiated with care to avoid damaging them.  

So you will normally need to allow a full day to insulate a typical loft (or half a day for two installers working in tandem). If you opt for more sophisticated materials or there are problems with restricted access, the job could take twice as long.  

Use loft stilts or legs to create a raised platform

Once the jobs complete its a good idea to fit special boarding above the new insulation using special “loft stilts” – a raised platform so as not to compress the insulation (which can seriously reduce its performance). Any reputable installer will include insulating the loft hatch as part of the job.   

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man wearing protective clothing to lay loft insulation in a large loft spaceCredit: Shutterstock / Eduard Goricev

Factors affecting how much loft insulation costs

Perhaps the most obvious factor affecting how much loft insulation will costs is how much insulation youve already got in your loft. In most cases this can be left in place as a base layer, which you can top up to achieve the magic 270mm (10.6in) recommended depth for loft quilt. Where there are a lot of smaller obstacles that cant be snugly encompassed within the new quilt, loose-fill insulation such as polystyrene beads or vermiculite can be sprinkled on by hand (wear PPE as a precaution). 

People often ask whether the type of house they live in will affect the cost of works. Checkatrade lists prices for insulating typical terraces, semis and detached houses respectively as £550, £670 and £930. But the difference is largely down to the size of the roof space being insulated.   

A more significant driver of cost is where a property has what’s politely known as a ‘challenging’ loft. Victorian houses often have small rear subsidiary roofs, or you might have bedrooms with sloping ceilings that need insulation from below, or maybe there’s no loft hatch at all.  

Where access is difficult or impossible, a good alternative solution can be to fix sheets of insulated plasterboard to the ceilings below using dry wall screws, before taping and jointing, skim plastering and decorating. Allow around £30 per sq m for the cost of buying insulated plasterboard (plus fixings etc), and an extra day or two for labour, depending on the size and complexity of the areas to be insulated.  

Don’t forget to check pipes and cables

Avoid burying electrical cables under new insulation

Before laying insulation, it’s important to check for pipes and cables. Once obscured under fresh quilt there will be few clues to their location, or to the whereabouts of joists that you can safely tread on. To help prevent injury and damage, special raised boarded walkways can be fitted (some of which have integral insulation).   

It’s advisable not to ‘bury’ any electric cables within insulation. But paying an electrician to re-route all the cabling could add several hundred pounds to the cost. In most homes, electric cables in lofts only supply the lights in the rooms below, and if these are all modern LEDs it’s unlikely an electrician would regard there was any significant risk of cables overheating. If it’s not possible to rerun cables above the new insulation, a good alternative is to fit lengths of split-sided conduit sheathing around them to form an air space.    

Although mineral-based insulation materials like Rockwool are inert and fireproof, where you’ve got recessed ceiling lights in bathrooms, etc, it’s advisable to fit downlight protection hoods over them (these look like upturned flower pots and cost about £7 each). 

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Loft Leg downlight protection, 4 pack, Amazon

To finish the job, any water tanks in the loft should be insulated with a lagging jacket, and any exposed pipework lagged with lengths of foamed tubing.  

Government grants for loft insulation – who qualifies?

The recently announced Great British Insulation Scheme offers free or discounted insulation upgrades for less energy-efficient properties in lower council tax bands. To qualify, your home needs to have a relatively poor EPC rating of D or below, and be in a council tax band A to D.

Ian Rock

Written by Ian Rock he/him


Ian Rock is a Fellow of the Royal Institution of Chartered Surveyors (RICS) and founder of the home survey price comparison website Rightsurvey.

Ian is the author of several best-selling property books, including The Haynes Victorian House Manual, Home Extension Manual and Loft Conversion Manual. He has written for The Observer and is a regular contributor to UK property magazines.