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Rafter insulation refers to the pitched part of a roof, which can be insulated with slabs or rolls depending on local availability.

ROCKWOOL rafter insulation helps to provide thermal, fire, and acoustic protection for roof spaces.

Made from natural stone wool, our products help to provide robust and durable insulation between, above, and below the rafters, depending on your project.

As the roof is an area where heat can be gained, installing the correct insulation is important to avoid high energy bills and unwanted noise pollution.

Find out how our insulation over, under, and between the rafters can boost the energy efficiency of your home or project.

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Why do we need rafter insulation?

It is important to enhance the energy efficiency of a building.

When a pitched roof space is created, occupants of loft living spaces are often exposed to high levels of external noise too, such as air traffic. This means that treating the roof acoustically is just as important.

With effective insulation, a roof area can become a comfortable living space. This can be installed in three main ways and often a mixture of the methods is required to complete a project.

Insulation in between rafters

Slabs and rolls for between the rafters are often combined with under and over the rafter insulation for optimal performance.

Insulation between the rafters is commonly placed in between the wooden beams to allow for more headroom. Insulation on the inside or outside is added to further improve thermal, fire or acoustic requirements.

When you place insulation above- and-between the rafter construction, ROCKWOOL solutions provide you with high acoustic performances. This can be a great advantage when building or renovating in areas with high sound levels, such as those close to airports.

Roger Peeters

Global Product Manager, ROCKWOOL Group

Calculator and savings

Roof rafter insulation is an affordable and energy-efficient solution for your project or refurbishment.

As each project is different, we can work with you to match the type and thickness of the insulation to almost any build specification – depending on your individual needs.

For slabs and rolls, it is relatively easy to estimate the amount needed by calculating the m2 of the roof area. When using sub-frames to install a finishing layer on the inside product, the width should be considered to reduce waste material.

Use our ROCKWOOL U-value calculator to determine the thermal performance of the building’s roofs and possible cost savings. For more details on technical specifications, visit our ROCKSPEC Specification Toolkit.

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Case studies

The State Hermitage, St Petersburg, Russia3

The project:

The State Hermitage is a series of lavish buildings housing paintings and artworks. Restoration work was required to make sure the building remained comfortable and safe, to preserve one of the world’s largest museums.

The problem:

Due to the building’s age and complexity, refurbishment of the roof needed to be carried out with the upmost care. As the weather can be extreme in Russia, with freezing winters and hot summers, the correct insulation needed to be used to maintain a comfortable temperature within the museum.

The solution

ROCKWOOL roof rafter insulation was selected as it can be sized to fit perfectly between uneven spaces, and provided the building with the perfect temperature maintenance required for such a large space.

Not only did it help to reduce energy bills for the museums, its fireproof qualities were also paramount for the preservation of such an old and important building.

The State Hermitage Museum

Sustainability and energy efficiency

ROCKWOOL insulation is designed with sustainability and enhancing the energy efficiency of buildings in mind.

It is developed from rock, one of the most sustainable and abundant natural resources on our planet. The earth produces 38,000 times more stone than we use annually to produce stone wool.4



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Financial support

For available grants and cost-saving initiatives, consult local resources and government websites for more information.

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