Loft & Attic Insulation

Homeowners lose up to 25% of the heat in their homes through their roofs. Investing in warm loft insulation can keep your home toastier for longer and reduce the amount of money that you spend on energy bills. Loft insulation rolls are easy to handle and install, which makes them a popular choice for people who want to improve the thermal envelope of their homes. Browse through our range of loft insulation rolls and PIR insulation boards to find the perfect insulation for your attic. 

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What Is Loft Insulation?

Loft insulation – sometimes referred to as attic insulation – is insulation that is designed for installation between rafters and joists in your loft. Homeowners lose up to a quarter of the heat in their homes through lofts that are not insulated, meaning your home is less energy efficient. When homeowners start to consider the long-term cost-saving impact of insulation, their loft is often the first space that they focus on.

Loft Insulation Best Types

Loft Roll Insulation
Loft insulation rolls are made from recycled glass wool (fibreglass insulation). Glass wool is an excellent insulator. Manufacturers make glass wool insulation by heating glass to extremely high temperatures. When the glass melts it is spun to create fibres. The glass fibres mesh together and create a blanket. Thousands of pockets of air are trapped between the glass fibres in the manufacturing process.

Loft roll insulation makes insulating an attic easy. You can simply buy a size that fits between your joists and roll the material into place. Most loft roll come pre-cut or “combi-cut”. All the rolls in the Knauf Earthwool Loft Roll 44 range have perforations at 570mm and 380mm centres which means that they can easily be split to fit between standard joist and rafter spacings.

PIR Insulation Boards
You can either buy loft insulation in rolls or boards. Rolls are the most popular choice for people who want to insulate their pitched roof attic floor. We recommend loft insulation boards for people who want to reduce heat loss through their pitched or flat roofs. The most popular of these is the PIR insulation board.
PIR (or polyisocyanurate) is an extremely popular insulation material and will make the loft space warmer compared to standard loft insulation. Manufacturers apply PIR foam to a layer of facing. The foam expands and adheres to the top layer of facing over time. Manufacturers stop this process at different times to achieve different thicknesses. They then cook the PIR board under extreme heat, cut it into smaller boards, and package it.
PIR has a thermal conductivity value of 0.022 W/mK, making it the best heat insulator on the market behind phenolic insulation. You can buy PIR loft insulation boards in a range of thicknesses from 20mm to 150mm and is perfect for pitched roof insulation. The facings in the boards provide extra protection against the elements, which is perfect for people in high rainfall areas.

Loft Insulation Between Rafters & Joists

Rafters are the beams that support your roof. Joists are the horizontal beams across the floor of your attic. It is a good idea to put loft insulation between rafters and joists to effectively improve the thermal envelope of your loft.
PIR boards are the go-to choice for people who want to install loft insulation between rafters. Whereas installing insulation rolls is difficult to hold in place, boards are rigid and firm. You do not have to worry about one end of the board falling and unravelling while you try to secure it.
Loft insulation rolls are the most common choice for joists. If you measure the space between them you can choose an exact fit. We stock a range of ready cut and perforated rolls that you can simply roll into joist space.

Loft Insulation Over Boards

Lots of homeowners install loft boards so that they can safely walk across and store items inside their lofts. Most loft boards are made from chipboard, which is a rigid and moisture resistant sheet material. They have tongues and grooves, meaning they can slot seamlessly together for an easy installation process.
Installing loft insulation and boarding is simple. We recommend laying attic insulation over the boards and installing another layer of boards on top. You must take the proper precautions to ensure that your insulation does not flatten. If your insulation is compressed too much by the weight of the boards it will become less efficient. You can use products like loft legs to ensure your insulation retains its shape.

Frequently Asked Loft Insulation Questions

Is Loft Insulation Flammable?

Loft insulation rolls have excellent fire-resistant properties. The rolls in our loft range are made from glass mineral wool. Glass is a fire-resistant material. Each roll contains thousands of small glass wool fibres, which are compressed to form just one of the layers inside each roll. Glass mineral rolls like Knauf Earthwool 44 Rolls have an A1 rating on the Euroclass scale, meaning they are anti-flammable.

All insulation materials have a Euroclass rating. The rating was designed to standardise the classification of insulation materials all over Europe. Materials undergo up to five tests which results in a classification from A1 (non-combustible) to F (very combustible).

PIR loft insulation boards are not non-combustible like glass mineral rolls. Celotex XR4120 PIR boards have a fire rating of E, whereas Recticel Eurothane GP PIR boards have a fire rating of F. You can use a build-up of other products to improve the overall performance of your materials against fire.

Is Loft Insulation Waterproof?

If you live in areas with high rainfalls, you should invest in PIR attic insulation boards. PIR has a closed-cell structure, which makes it resistant to moisture. It is perfect for people who want to install loft insulation between rafters that will maintain its thermal properties over time. You can install waterproof sheets over boards and between rafters to ensure the insulation maintains its thermal performance. We recommend loft insulation boards for people who live in areas with high rainfalls.

Despite being exposed, glass mineral wool is hydrophobic. It does not absorb water. You do not have to worry about mildew when you choose glass wool insulation. Like PIR boards, glass mineral wool insulation rolls work the best when they are protected with waterproof layers.

Which Loft Insulation is Best?

This really depends on what you are trying to achieve with your loft insulation. Most people install loft insulation to improve the thermal envelope of their building and reduce heat loss. Using PIR insulation boards at rafter level and loft insulation rolls at joist level is a very popular method for insulating a loft and will definitely improve the heat retention of the space.

If you want to go above and beyond to insulate your loft, you can use an insulated plasterboard such as Celotex PL board to add an extra layer of thermal protection to the attic space. This product can be mechanically fixed to the underside of the rafters, leaving a smooth plasterboard finish facing into the loft, and adding an extra layer of insulation at rafter level.

What is the Cost of Loft Insulation?

Unless you’re a multi-millionaire, cost is always an important factor when assessing any building project, and installing loft insulation is no exception. When weighing up the cost of loft insulation, it is also important to consider the long term benefits of properly insulation your loft space, and what this might save in future heating bills. While paying a bit more for your attic insulation means a higher up front cost, you are likely to get this back over the coming years as you will have a more thermally efficient building.

While loft insulation rolls are the cheapest form of loft insulation, they are also the least thermally efficient, with a thermal conductivity of just 0.044 W/mK. Therefore if you decide to install loft roll between the joists in your attic, it is important to balance this by using a more thermally efficient product – such as PIR insulation board – in the roof.

While cost is an important factor, you should always weigh up the long term benefits before deciding to prioritise price over quality. We have some of the cheapest prices on attic insulation of any online supplier. However, cheap doesn’t mean low quality – with industry leading brands such as Knauf Insulation and Celotex – you’re sure to find effective loft insulation that won’t break the bank.