If your home feels cold, your heating bills are high, or your loft is poorly insulated, roof insulation can be one of the best upgrades you can make. A well-insulated roof helps keep heat inside your home, reduces wasted energy and can make your property feel more comfortable throughout the year.
The price of roof insulation will depend on:
- The type of insulation you choose
- The size of your roof or loft space
- The condition of the area
- How easy it is to access.
The final cost can also vary depending on whether the work is carried out in a standard loft, between the rafters, as part of a flat roof project, or during a full roof replacement.
This guide explains the main types of roof insulation, how much they usually cost, how long they last, and when each option is normally recommended.
How Much Does Roof Insulation Cost?
As a general guide, roof insulation can cost between £10 and £50+ per m², depending on the material and installation method.
For a typical 20m² area, you may expect prices such as:
|
Type of insulation |
Where it is used |
Average cost |
|
Loft floor insulation |
Between and over loft joists |
£300 to £750+ |
|
Between-rafter insulation |
Under a pitched roof slope |
£600 to £1,500+ |
|
Warm roof insulation |
Above the roof deck |
£1,000 to £4,000+ |
|
Cold roof insulation |
Between joists or rafters with ventilation |
£500 to £1,500+ |
|
Flat roof insulation |
Flat roofs, usually warm deck systems |
£600 to £2,000+ |
These figures are only a guide. The final roof insulation cost will depend on your property, the condition of the roof, the insulation material, and whether extra work is needed.
Roof Insulation Types
As mentioned briefly above, the cost of roof insulation can vary depending on the type of insulation you need for your property. Below, we’ve broken down each type of insulation, where it’s used, the average cost, alongside some advantages and disadvantages so you can easily make a decision.
Loft Floor Insulation
Loft floor insulation is one of the most common and affordable ways to insulate a home. It’s installed between and over the joists on the loft floor, meaning the insulation sits above the ceiling of the rooms below, which helps stop heat from escaping into the loft.
Where Loft Floor Insulation Is Used
You’ll find loft floor insulation in homes where the loft is mainly used for storage or left as an unused roof space, and it’s suitable for many standard pitched roof homes.
It keeps the living space below warm, while the loft itself remains cold.
Average Lifespan
Loft floor insulation can last around 30 to 40 years if it’s installed correctly and kept dry. However, its lifespan may be shorter if it becomes damp, compressed, damaged by pests, or moved during other work in the loft.
Average Cost
You can expect the average cost of loft floor insulation to be around:
- £10 to £20 per m² for basic mineral wool or fibreglass insulation
- £300 to £750+ for many standard loft spaces
- More for larger properties or where old insulation needs removing
If your loft already has some insulation, it may only need topping up to the recommended depth. This can cost less than a full new installation.
Advantages
- One of the most affordable roof insulation options
- Quick to install in many homes
- Effective at reducing heat loss
- Suitable for many standard loft spaces
- Easy to top up if existing insulation is too thin
Disadvantages
- The loft space itself stays cold
- Pipes and water tanks in the loft may need extra insulation
- It may not be suitable if you want to use the loft as a heated room
- Storage boards may need raising to avoid compressing the insulation
- Poor ventilation can cause condensation issues
When Is Loft Floor Insulation Recommended?
Loft floor insulation is recommended when you want a cost-effective way to improve warmth and energy efficiency, but you do not use the loft as a living space.
If you’re a homeowner who wants to reduce heat loss without carrying out any major roofing work, this option could be perfect for you.
Between-Rafter Insulation
Between-rafter insulation is fitted between the sloping rafters of a pitched roof. This method insulates the roof slope itself, rather than insulating the loft floor.
This helps create a warmer roof space, which is often used when a loft is being converted or used more often than it would be as a simple storage space.
Where Between-Rafter Insulation Is Used
Between-rafter insulation is used in pitched roofs where the insulation needs to follow the roofline. You’ll typically find it in:
- Loft conversions
- Attic rooms
- Homes where the loft is used as a functional space
- Pitched roofs where floor insulation is not suitable
Rigid insulation boards are often used between the rafters because they provide strong thermal performance without taking up too much space.
Average Lifespan
Between-rafter insulation can last around 25 to 40 years, depending on the material and how well the roof is ventilated. However, the insulation should remain dry and properly fitted, as if moisture enters the roof space, performance, lifespan, and effectiveness can reduce over time.
Average Cost
The average cost of between-rafter insulation is usually around:
- £30 to £50+ per m² for insulation boards or specialist materials
- £600 to £1,500+ for smaller pitched roof areas
- More if plasterboard, finishing work or ventilation upgrades are needed
The cost can rise if the rafters are shallow, uneven, or difficult to access.
Advantages
- Help create a warmer loft or attic space
- Be useful for loft conversions
- Improve comfort in rooms built into the roof
- Provide good thermal performance with rigid boards
- Reduce heat loss through the pitched roof slope
Disadvantages
- It costs more than basic loft floor insulation
- It can reduce headroom if extra insulation is needed below the rafters
- Ventilation must be handled correctly
- Poor installation can lead to condensation
- It may involve more disruption than loft roll insulation
When Is Between-Rafter Insulation Recommended?
Between-rafter insulation is recommended when the loft space needs to be kept warm, such as:
- Loft conversions
- Attic rooms
- Roof spaces used for more than basic storage
It’s also a good option when you want insulation to follow the roofline rather than sit across the loft floor.
Warm Roof Insulation
Warm roof insulation is installed above the roof deck. This keeps the main roof structure on the warm side of the insulation, which helps reduce the risk of condensation.
Warm roof systems are common on flat roofs, but they can also be used on pitched roofs during more significant roofing work.
Where Warm Roof Insulation Is Used
Warm roof insulation is often used when:
- A flat roof is being replaced
- A new flat roof is being installed
- A pitched roof is being fully refurbished
- A home extension is being built
- A high-performance roofing system is needed
Because the insulation sits above the deck, it is usually installed as part of a larger roofing project.
Average Lifespan
Warm roof insulation can last around 30 to 50 years, depending on the roofing system, materials, and workmanship. However, to properly protect the insulation from water damage, the roof covering the insulation must be maintained properly.
Average Cost
The average cost of warm roof insulation can vary widely. As a guide:
- £50 to £120+ per m² may be expected for many warm roof systems
- A small flat roof may cost from around £1,000 to £2,500+
- Larger or more complex roofs can cost £4,000+
The price will usually include more than insulation alone, as the roof covering, boards, and detailing may also be involved.
Advantages
- Strong thermal performance
- Helps reduce condensation risk
- Keeps the roof deck warmer
- Suitable for flat roofs and extensions
- Often used as part of a long-term roofing upgrade
- Can improve the overall performance of the roof
Disadvantages
- Higher upfront cost
- Usually needs professional installation
- Often involves removing or replacing parts of the roof
- More disruptive than loft floor insulation
- Not always necessary for simple loft spaces
When Is Warm Roof Insulation Recommended?
Warm roof insulation is recommended when a flat roof is being replaced, a new extension is being built, or the roof needs a more complete upgrade.
It’s often the preferred option for flat roofs in particular because it helps improve thermal performance while reducing condensation risk.
Cold Roof Insulation
Cold roof insulation is installed below the roof deck, usually between joists or rafters. In a cold roof system, the roof deck remains on the cold side of the insulation, so ventilation is very important.
This method is common in older roofs and some flat roof structures.
Where Cold Roof Insulation Is Used
Cold roof insulation can be used in:
- Some pitched roof spaces
- Older roof structures
- Certain flat roofs
- Lofts where insulation is placed below the roof covering
- Areas where a warm roof system is not being installed
A cold roof system must allow air to flow above the insulation, because without the right ventilation, moisture can build up.
Average Lifespan
Cold roof insulation can last around 20 to 40 years, depending on the material and ventilation. However, if the roof space becomes damp, the insulation may lose performance and need replacing earlier.
Average Cost
The average cost of cold roof insulation is usually around:
- £20 to £50 per m²
- £500 to £1,500+ for many smaller roof areas
- More if ventilation improvements or repairs are needed
Cold roof insulation can be cheaper than a warm roof system, but the installation process can be more tedious.
Advantages
- Often cheaper than warm roof insulation
- Suitable for some existing roof structures
- Less disruptive in some cases
- Good for certain loft and roof layouts
- A practical option when warm roof work is not possible
Disadvantages
- Ventilation is essential
- Greater risk of condensation if installed badly
- Not always suitable for flat roofs
- Can be harder to detail correctly
- May not perform as well as a warm roof system in some situations
When Is Cold Roof Insulation Recommended?
Cold roof insulation may be recommended when a warm roof system is not practical, or when the roof structure is already designed to work as a cold roof.
Before you choose cold roof insulation, your property should always be assessed by a professional because ventilation is a key part of the system.
Flat Roof Insulation
Flat roof insulation is used to improve the thermal performance of flat roofs on extensions, garages, dormers, and commercial buildings.
Most modern flat roofs use a warm roof build-up, where insulation is installed above the roof deck and below the waterproof covering.
Where Flat Roof Insulation Is Used
Flat roof insulation is used on:
- House extensions
- Garages
- Dormer roofs
- Porches
- Outbuildings
- Commercial flat roofs
- Replacement flat roof projects
It is often installed at the same time as a new felt, GRP, EPDM, or other flat roof covering.
Average Lifespan
Flat roof insulation can last around 25 to 50 years, depending on the roofing system and whether the roof covering remains watertight. If water does manage to get through the roof covering, the insulation can become damaged and may need replacing.
Average Cost
The average cost of flat roof insulation is usually around:
- £50 to £120+ per m², depending on the system
- £600 to £2,000+ for many smaller flat roofs
- More for larger flat roofs or where the existing roof needs stripping back
If the insulation is being fitted as part of a full flat roof replacement, the total project cost will typically include the new roof covering as well.
Advantages
- Improve warmth in the room below
- Reduce heat loss through the flat roof
- Help prevent condensation when installed correctly
- Improve the performance of an older flat roof
- Work well with modern flat roofing systems
Disadvantages
- It can be more expensive than loft floor insulation
- It is usually best done as part of a flat roof replacement
- Poor installation can lead to water pooling or leaks
- The waterproof covering must be fitted correctly
- Existing roof damage may increase the final cost
When Is Flat Roof Insulation Recommended?
Flat roof insulation is recommended when a flat roof is being replaced, upgraded or newly built. It is also worth considering if the room below a flat roof feels cold, suffers from condensation, or loses heat quickly.
Process of installing roof insulation
It’s important to know the steps involved in installing roof insulation before you choose a certified contractor. The type and size of the roof
to be insulated will be determined by a roof installation professional before you hire a tradesperson to complete the installation for your property. When choosing the level of quality and materials you want to use, they will go over all of your alternatives with you.
Installing roof insulation is a straightforward process. The first step is to have an expert evaluate your home’s roof and determine the type and size of the insulation required.
A skilled roof insulation crew can start installing your new insulation once the area is tidy and clear of any obstacles. In most cases, the procedure lasts just a few hours and is finished in a day or less. It may take longer, though, depending on your roof’s complexity and the scope of the project.
They will also look at the ease of access to your roof, ensuring that there are no obstructions or dampness in the attic space.
Finally, they will clean up after themselves so you don’t come home from work one day to find yourself covered in dust!
Roof Insulation Material Options
When it comes to choosing the right type of insulation material for your roof, there are many options available. Here are some of the most popular choices amongst homeowners:
- Fibreglass Wool: This is a popular choice amongst homeowners because it’s less expensive than other types of insulation and easy to install. It also lasts longer and provides excellent thermal performance. This top-notch insulator is an affordable option that can be bought in lengthy rolls, making it a sensible choice. Fibreglass wool insulation typically costs about £25 per square metre.
- Mineral wool Insulation: This material is made from rock minerals and can be installed in either roll form or as batts with tapered edges that fit snugly into place between rafters. This type of insulation is eco-friendly and has excellent thermal performance but may have higher installation costs due to its heavier weight compared with other types.
- Sheep Wool Insulation: You might want to think about using sheep wool insulation if you’re seeking a more environmentally friendly choice. Sheep wool is offered in huge rolls, just like rock and fibreglass wool. However, purchasing this natural alternative will cost you significantly more, possibly between £50-£60 per square metre. When compared to other forms of insulation, sheep wool is significantly more pleasant to deal with and less irritating.
- Plastic or polyester fibre: These types of insulation are less hazardous to handle than sheep wool insulation and are comparable to that material. They are also a more environmentally responsible option because they are frequently produced from recycled materials. Sheep wool insulation is typically more expensive than plastic and polyester insulation, which is why fibreglass is more economical. Polyester insulation will typically cost about £35 per square metre.
Want to install roof insulation to your home?
Now that you are aware of the roof insulation cost, you’re in a better position to communicate with the roofing contractors to ask for quotations and advice. If you would like our help, then please contact the team here at LD Roofing Services Ltd for a free quote and consultation today!