I wonder how many of you have actually been in your loft more than once in the last 5 years. Not many I expect (except for packing away the Christmas decorations). For many homeowners, the loft beneath their roof (also called an attic or roof space) is an undiscovered country. It’s a place that they never think about from one week to the next. Yet, did you know that with only a small financial outlay, you can turn a roofspace into a highly effective layer of insulation. Also, it’ll save many hundreds of pounds on your heating bill every year?
Most people know that hot air rises, but have you ever thought about where the warm air from your radiators goes to? Well, it rises through the house until it reaches the bedroom ceilings. If there isn’t any insulation in the loft, the heat disperses through that space into the outside world. However, all you need is a layer of insulation to separate the cold air from the warm and you won’t lose that precious and expensive heat. Have I whetted your appetite yet? Do you want to save money and re-use the heat that would otherwise be lost? Carry on reading and find out how much insulation costs, how much you’d save, and the best way to insulate your loft or attic.
On average, the cost of loft insulation, about 100mm thick will be £2.50 per m2. However the current Building Regulations recommend 270mm of insulation, so you’ll want 3 layers of 100mm thick. This calculates to about £290 for a 3 bedroom terraced house.
In practice, the total cost of using loft insulation will vary depending on which type you use, the size of the loft floor and how thick you lay the insulation (remember the recommended thickness is 270mm). The Energy Saving Trust suggests that if you have a standard British home with gas central heating and standard fibreglass insulation, you can calculate the costs, similar to those shown in the table.
|Cost of insulation||Heating bill savings per year||Payback time|
|£395||£215||12 to 24 months|
|£300||£130||12 to 48 months|
|£285||£115||24 to 36 months|
|£375||£185||12 to 24 months|
Types of loft insulation
In theory, anything with air pockets is an insulating material. Because motionless air is a very poor conductor of heat. However, in practice, we use only those materials that are easy to transport and install, won’t be a fire hazard, are relatively cheap, and those that prevent heat loss. Bear in mind that the recommended loft insulation thickness calculates to about 270mm for minimum heat loss.
These are the most popular choice. They’re fibrous materials sold in rolls or slabs (also called batts). They’re usually made from mineral or glass fibre, but there are brands made from non-irritant sheep wool. This type of cheap loft insulation comes backed with a vapour barrier paper. But, more expensive products have a foil backing to reflect radiant heat. The advantages of this type of insulation are:
- DIY friendly and very easy to install.
- Easy to install into exposed cavities.
- Relatively cheap to buy. A roll of loft insulation covering 8.3m2 x 100mm thick will cost about £20. So three rolls giving 300mm thick costs about £60.
Disadvantages of blanket insulation include:
- Some types irritate the skin and damage the lungs if inhaled.
- Very bulky rolls won’t fit in small enclosed spaces.
- Some types are expensive, such as sheep’s wool.
- Wear suitable protective clothing.
Various lightweight granular materials make up this type of loft insulation material. Typically, cork granules, cellulose fibre, mineral wool and recycled newspaper. Manufacturers treat naturally flammable materials such as the cork, cellulose and paper to prevent fire so it’s no longer a hazard.
Advantages of loose–fill insulation include:
- Easy to carry and pour into irregular cavities and around obstructions.
- Sometimes used as a top-up for existing insulation.
Disadvantages of loose insulation include:
- Easily blown about in draughty lofts.
- Although these don’t usually irritate the skin, they produce dust which, when inhaled causes problems.
- Use appropriate safety equipment during insulation.
Also known as roof insulation board, this type insulates between the rafters (the sloping sides of the roof). They’re made from foam polyurethane or polystyrene sheets sandwiched between foil or other coverings. Greener versions use compressed cork or straw. It’s always fire resistant and moisture resistant and sometimes has a decorative finish. However, they’re usually covered in plasterboard after installation.
Advantages of sheet insulation include:
- If you insulate the sloping roof, you bring the roofspace into the building’s thermal envelope. It’s great for loft conversions.
- Usually, covered with plasterboard for a decorative finish.
- Very good insulator for its thickness.
- Polyurethane and polystyrene sheets use large amounts of energy during manufacture.
- Sometimes they’re expensive compared to other insulation types.
Blown-fibre loft insulation
This isn’t a DIY method as specialist contractors blow this insulation into place between the joists.
Advantages of blown-fibre insulation include:
- Easy to install by a professional.
- Options include wool or paper.
- Good for insulating difficult–to–access areas.
- Light and convenient.
- Blown-in insulation costs are expensive.
- A problem if the loft is draughty.
Spray foam loft insulation
Chemical aerated foam, sprayed between the rafters on the roof. You need a specialist with equipment for this job, so it’s expensive. However, it brings the roof space into the house’s thermal envelope and allows you to board the floor or convert the loft into a living area.
Advantages of spray foam insulation include:
- The roof space will be warmer than with any other insulation.
- No more freezing tanks and pipes.
- It will block even the smallest hole to the outside, preventing draughts.
- You can board the floor without raising the joist level.
- Needs a professional to do the work.
- It costs more than most other insulating methods.
- You’ll need to insulate all the other exposed surfaces as well. Areas like gables, chimney breasts and party walls, otherwise the heat will escape through those surfaces.
If you or someone in your home belongs to a vulnerable group or receives certain benefits, some energy suppliers will help towards the cost of insulation. Otherwise, different schemes can help with the cost of heating or insulating your home. You often have to buy the materials first and then claim back any costs against these loft insulation grants. Also, they often have a qualifying date after which you can no longer claim back the loft insulation costs. If this is the case and you rely on the home grant to cover the cost, make sure you check the details before doing the work.
Do it yourself
If you have an accessible loft, in which you can move about, and don’t have damp problems, then insulating is one of the easiest DIY jobs. Not only that, but it will also save a lot of money too. But, if you have damp in the roof, or have a flat roof then you must get an estimate from a professional to do the work.
The best roof insulation to use when attempting a DIY project is always going to be blanket material. Try to cover as much of the floor area as possible with this and finish off with loose–fill insulation to top up in places that are difficult to reach.
Things to remember
Although insulating your loft will make your living areas warmer, it’ll also make your roofspace colder. Therefore, if you’ve any water tanks or pipes in the loft, insulate them separately from the rest of the space before you insulate the floor. Otherwise, during a cold winter, the water inside might freeze. Also, don’t insulate underneath a water tank. Keeping this space clear will also help to prevent the tank from freezing. Don’t lag the water tank and pipes with the same insulation as the floor. Instead, buy an insulating jacket specifically designed for make and size of the water tank together with an insulated lid. You can also buy lengths of pipe insulation to suit the diameter of pipes. Cut and fit these to each pipe and tie in place with plastic cable ties.
if you have a tank or television antenna inside your loft you’ll need access now and again. So, if you don’t intend boarding out the entire loft floor, provide a walkway from the hatch to those items.
If you’ve laid 270mm insulation across the floor, raise the floorboards. Probably, the best way is to fit adjustable legs to the existing joists, that provide support for the floorboards at the required height. If you intend to fix anything to the joists, don’t use nails. The impact of the hammer will disturb the nails in the ceiling below. Use screws instead.
Pay attention to the loft hatch as well. A cold loft causes heat loss through the hatch and cool draughts working their way around the edges of the hatch. Insulate the hatch’s entire area and fix draught excluders to the edges. If you have problems fitting blanket insulation to the top of the hatch, it might be better to glue layers of insulation board instead.
There are some Building Regulations you must follow when insulating a roof.
- When you renew more than 25% of a roof, you must renew the insulation to the thickness required by the Building Regulations. Currently 270mm for fibreglass.
- The recommended thickness of other insulation materials will vary depending on its thermal conductivity. However, keep the value equivalent to 270mm of fibreglass.
- Don’t block any ventilation ducts or tiles at the eaves. Otherwise, you will encourage condensation.
- You can place insulation either between the joists or between the rafters.
- If you lay floorboards in the loft, you must not compress the insulation to alter its thermal conductivity.
Loft Insulation Cost FAQ
Is it worth topping up loft insulation?
If you have less than 270mm thickness of insulation then definitely top it up. If you add more than this thickness you won’t benefit from it. The extra few pounds you save will be far less than the extra cost of materials and labour.
how much loft insulation do I need?
You’ll need 270mm of fibreglass or the equivalent depth using insulation of different materials. It wasn’t very long ago that the recommended depth was 100mm so it’s worthwhile measuring how deep your existing insulation is at present. Once you know how much you have, top it up.
Can you put too much insulation in an attic?
You can install as much insulation as you like as long as you don’t interfere with the ventilation you need to prevent condensation. It’s a case of achieving a balance between the two.
Is spray foam better than fibreglass?
Yes. Although it’s easy to install fibreglass, if it’s not fitted properly you can easily leave spaces through which you’ll lose heat. On the other hand, the foam will fill all cavities and prevent heat loss from below. Also, foam is more efficient than fibreglass and has a higher R-value so you’ll need less thickness.
How can I remove old insulation?
That depends on the type of insulation you have.
If it’s fibreglass, roll up the blankets and place them into bin liner bags. Then, use a vacuum cleaner on all the little bits. Remember to use a dust mask during the operation. Blown and cellulose insulation can be vacuumed out with specialist equipment. Ask a contractor to do this.
Leave foam where it is until it starts to peel away from the surface. Then bag it up. Remember that you must dispose of all old insulation responsibly. Make sure you comply with all local and national laws and regulations.
Who can install loft insulation?
Insulating your loft is always worthwhile. It’ll reduce your heating bills and make your home much more comfortable than before.
If for any reason you can’t insulate your loft, don’t worry. There are plenty of contractors out there who can do the job. Just contact a reputable professional and ask for a quotation.
Contact the National Insulation Association (NIA). They have a register of approved insulation installers. Their members agree to abide by a code of conduct so that all their customers receive a professional standard of work and good customer service.
Alternatively, if you want us to find a contractor for you. Complete the form on this page and you’ll receive 3 or 4 estimates from qualified local contractors. They’ll charge you standard loft insulation prices and save you the problem of climbing into the loft.