How to insulate a loft and reduce energy bills

What’s in your loft? Apologies if it sounds like a personal question, but the fact of the matter is that learning how to insulate a roof – or at least the loft underneath that roof – could stop a quarter of the heat that escapes from your house to the air outside. That’s how much is getting through your non-insulated loft, and it’s why the pigeons and seagulls sitting on your roof have got that smug expression on their faces. You’re paying good money each and every day to keep the rear ends of those birds lovely and snug. Perhaps you’re enough of a bird lover to consider that money well spent, but if you’d rather knit them little pants and get round to cutting your energy bills then rest assured – a loft which is full of nothing but old suitcases, the Christmas tree and those vinyl records you’re certain will be worth a fortune one day is one of the reasons your bill is so high. The good news is that insulating a loft will save you money, will last for up to 40 years and is something which you can tackle yourself. The even better news, if you’re wondering how much it costs to insulate a loft, is that some energy suppliers run schemes offering to provide loft insulation free of charge. This offer is part of the Energy Company Obligations (ECO) scheme, which is run by Ofgem and obliges energy companies to provide free energy saving services such as loft insulation to customers on specific benefits like tax credits. They’re available to people who own their own home, but if you rent from a social housing provider there’s a good chance they’re involved in similar schemes, so it’s worth contacting them to find out.

Companies currently providing loft insulation to new and existing customers via the ECO scheme include:

  • E.on
  • EDF
  • Npower
If you don’t qualify for any of these schemes then rest assured that the cost of having loft insulation fitted, according to the Energy Saving Trust, ranges from £285 to £395, and that if you do it yourself this could drop as low as £150. When the same trust calculates that loft insulation could save the average bill payer between £120 and £225 a year, these figures start looking less like expenses and more like sound investments. It effectively pays for itself in no time at all.

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Roof insulation methods

Provided your loft is in reasonably good condition and free from damp it should be relatively simple to insulate it yourself. The first stage involves clearing out the debris which any sensible person shoves up into the loft as the years go by. Once the loft is emptied, you should clearly be able to see the joists – horizontal beams which run along the floor of the loft.

There are two main methods of insulating a loft:

  1. Place insulating material between the joists to stop heat rising from lower in the house.
  2. Place insulating material between the rafters. The rafters are the angled beams which you’ll be able to see supporting the roof of your house.
  3. If you’re planning on insulating your own loft, then the first method is by far the simplest. If the space between the joists is regular then you can fill it using rolls of blanket roof insulation, which can be purchased from larger DIY stores or builders merchants. Once you’ve emptied the loft, the basic steps are as follows:
  4. Lag any water pipes and tanks in the loft, as the loft will be much colder once your insulation is in place.
  5.  Check that no wiring will be trapped beneath the insulation. If it will be then don’t attempt to stretch it to lift it higher yourself, but consult a professional electrician about having it shifted. You’ll be grateful you decided to do it this way – doing everything yourself might seem cheaper short-term, but you really don’t want to risk getting things wrong and losing all the money you saved by insulating the loft in the first place.
  6. Measure the loft and make sure you have enough insulating material to cover the whole of the surface up to a depth of at least 270mm. The last thing you need is one tiny gap that undoes the rest of your good work.
  7. Measure the joists in your loft. They’re generally around 100mm high, and your first layer of insulation should be as thick as the joists are high. Unroll the insulation running lengthways between the joists, cutting the roll with a pair of scissors to make sure it fits.
  8. When you’ve filled the space between the joists in this direction, lay a second layer of insulation at right angles to the first. The blanket you use this time should be 200mm thick, bringing the total thickness of insulation in your loft up to 300mm, which is enough to stop warm air escaping from your house.
  9. Believe it or not, that’s the job done, and an annual saving of more than £120 on average.


If you still want to store items in your loft, you’ll have to lay boards over the insulation. If you just cram 270mm of insulation blanket between your 100mm joists and then nail boards on top, the insulation will be too compressed to do the job. One solution is to line between the joists with 100mm of material as before, and then cover the joists with special insulating board to complete the job. Another solution is to hire a carpenter (or find a DIY-loving friend) capable of lifting the height of the floor to the required 270mm, leaving you with enough room to fit the insulation.

If you’re wondering how to reduce your energy bills in addition to lining your loft with a thermal blanket then wonder no more.

Touch base with Look After My Bills and we’ll make sure that the heat you’re trapping inside your house costs you less than ever.