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Roof and loft insulation





NOTE: Savings dependent on receiving a government grant otherwise there are long pay-back periods

Did you know that in an uninsulated home, up to 35% of heat can be lost through the roof? Insulating your loft, attic or flat roof is a simple and effective way to reduce heat loss, reduce your heating bills and reduce your carbon footprint.

Loft insulation is effective for at least 42 years and it should pay for itself many times over. Not only does it make your home warmer in winter, it also helps keep it cooler in summer. Air is a poor conductor of heat, so the tiny pockets of air trapped in insulation minimise the amount of heat which can pass between the inside and outside of your house. Keeping the warmth in your home reduces the risk of dampness and subsequent mould growth. Also, a warmer house is healthier for everyone, especially children and seniors who feel the cold more than able-bodied adults.

If you decide to install your own loft insulation, look out for the Energy Saving Trust Recommended logo to ensure you are buying insulation products that have been through a quality-control process and comply with building regulations.

* UK government guidelines now stipulate a minimum insulation depth of 270mm.


Everyone is potentially eligible for 50% – 100% grants, have a look at –


According to The Energy Saving Trust the average installation cost of loft insulation is around £890 and can save between £330 (= 606kg CO₂) and £590 (= 1085kg CO₂) a year on energy bills.

Note: loft insulation varies in price according to the type installed and can cost more than £2,500.

A grant will mean instant savings, but if you have to pay for installation there will be an extended payback period of up to 5 years.

Also, we indicate the CO₂e savings when you install loft insulation, but it’s important to understand that the environmental benefit of a reduced CO₂e footprint due to insulation only starts once the embedded CO₂e in an insulation material as well as the CO₂e generated during its transport and installation is removed from the equation.

Types of roof and loft insulation

1. Spray foam roof insulation

2. Rigid insulation boards

3. Blanket insulation

4. Loose fill insulation

1. Spray foam roof insulation

This is an expensive method of insulation, a semi-detached 3 bedroomed house would cost around £2,500.

Spray foam insulation is a liquid foam which is applied to the underside of the roof directly onto the slates, tiles or roofing felt and to the load bearing rafter timbers and sets into an insulating layer.

It has been in use for more than 30 years and is now becoming increasingly popular as it’s an effective insulator and can also stop air leakage.


  • Spray foam systems give greater acoustic insulation than conventional fibreglass and other forms of insulation. At 75mm thickness, the acoustic benefit is generally accepted to be equivalent to double glazing.
  • A spray foam system guarantees a warmer property in the winter and a cooler property in summer providing greater energy efficiency and comfort.
  • As many allergy sufferers will confirm, dust can make everyday activities unbearable. A spray foam system significantly reduces wind driven dust being blown into the loft space.
  • A spray foam system provides a stronger more stable roof due to the high strength to low weight ratio of the foam.
  • A treated roof can provide an opportunity for low cost loft conversion.
  • Spray foam is inert and does not provide any nutritional value to rodents, birds or insects, which also prevents vermin gaining access to your loft space.


  • It’s more expensive than other types of insulation
  • It needs to be installed by a professional
  • It can be difficult to remove once it’s been installed
  • Potentially reduces ventilation within the roof space, causing humidity and damp; placing roof timbers at risk of decay
  • Harmful fumes are given off during installation
  • It shouldn’t be used in listed buildings or houses with thatched roofs
  • It’s often ugly, messy and can’t be decorated over
  • In some circumstances mortgage companies will not give a loan when foam insulation is installed
  • We’d strongly advise getting specialist advice from an expert or two in this area and proceeding with caution.

2. Rigid insulation boards

If you want to use your loft as a living space, you can insulate your room-in-the-roof by insulating the roof with fixed rigid insulation boards between the roof rafters. Boards must be cut to the correct width so that they fit snugly between the rafters. They can then be covered by insulated plasterboard. Similarly walls in the roof space and around dormer windows should also be insulated with rigid insulation boards. In all cases make sure there is adequate ventilation to the rafters.


  • Greener insulation options include cork, straw and wood board.
  • Excellent for insulating loft conversions.
  • Can be covered with plasterboard for an attractive finish.
  • High insulating value per unit thickness.
  • Some boards come with their own system of attachment.
  • Ideal for fitting between rafters on a sloping roof.


  • Synthetic sheet insulation materials use large amounts of energy during production which means a longer environmental payback period.
  • Can be more expensive than other types of loft insulation.
  • You may need a professional to install the boards

3. Blanket insulation (also called matting insulation)

This insulation is available as simple rolls of varying thickness and width or rolls of foil-backed felt, rock, glass mineral fibre or flameproofed sheep’s wool. If access is easy and your loft joists are regular, you can use rolls of blanket insulation. The first layer is laid between the joists – the horizontal beams that make up the floor of the loft – then another layer is laid at right angles to cover the joists and make the insulation up to the required depth (270mm). The most common types of insulation in the home are made primarily using glass or rock that has been melted down at temperatures well in excess of 1,000°C and spun into fine strands of wool. A binding agent is also added to help hold the strands together. These strands of wool are then formed into the rolls to fit between ceiling joists.

Blanket insulation materials can be used in a wide range of buildings:

  • Commercial buildings such as shops and offices.
  • Public sector buildings such as schools and hospitals.
  • Residential houses and flats.


  • The world’s most popular and widely used insulation material, glass wool is made from up to 86% recycled materials, so it is ultra-eco-friendly. It is easy to handle and install, plus it is the most cost-effective insulation available.
  • Mineral wool consists of up to 70% recycled materials
  • Mineral-wool and fibreglass are sold in thicknesses to comply with the Building Regulations and are resilient to heat and fire
  • Rock mineral wool insulation is a more solid material than glass wool and is suitable for situations where the material may be compressed
  • Their widths are the same as the standard gap between joists.
  • Sheep’s wool is a natural material
  • They’re easily carried and handled.
  • Easily installed as a DIY project.
  • Mineral-wool and fibreglass don’t attract rats or other rodents.


  • Mineral-wool and fibreglass produce sharp dust particles when handled. Use protective clothing and a suitable dust mask.
  • Sheep’s wool doesn’t have a standard thickness or width. Therefore, it needs cutting to size. It may also need an intensive cleaning process in order to remove the dirt and oils from the wool. The chemicals and energy used during this process must be taken into account when measuring its environmental impact
  • Sheep’s wool might attract rodents and other pests into the loft.
  • You must cut all blanket insulation around obstacles and in small spaces.
  • Sheep’s wool is more expensive than other blanket insulation.

4. Loose fill insulation

​If your loft is hard to access, you can have blown insulation installed by a professional into the gaps between joists, they will use specialist equipment to blow loose, fire-retardant insulation material such as cellulose fibre, mineral rock wool, cork granules or even recycled newspaper into the loft. Loose-fill insulation works well in inaccessible spaces and for topping up.


  • Fits easily between irregularly spaced joists or around obstructions.
  • Greener insulation options include recycled paper or wool.
  • Ideal for insulating areas where access is difficult.
  • Light and convenient to handle.
  • Useful for topping up existing insulation in attics.


  • ​Can come loose in draughty lofts.
  • Can be more expensive than other types of loft insulation.
  • You’ll need to employ a professional to install blown-fibre insulation in your loft
  • Not recommended for insulating draughty lofts.
  • Safety equipment and protective clothing are needed during installation.

Possible problem – damp lofts

Insulation stops heat escaping from living spaces, so it will make your loft space cooler. This could introduce or worsen existing damp or condensation problems. If you are installing loft insulation, be aware that you may need to increase ventilation.

Energy Performance Certificate (EPC)

​An Energy Performance Certificate (EPC) shows how energy efficient a house is, and you will need an EPC when you want to sell your house. A home’s EPC shows an overall energy-efficiency rating for your home from A-G. ‘A’ represents the most energy efficient properties and ‘G’ the worst. The EPC also contains advice on how to cut carbon emissions and fuel bills by making home improvements.

​Fitting insulation is an effective way of raising your home’s energy-efficiency rating. If you don’t have insulation installed, the EPC will recommend the type and level of insulation required for maximum efficiency.