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

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 up to 25% of heat can be lost1, 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.

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.

 

Insulation under rafters

Insulation under rafters is placed between battens. Under the rafter insulation is often a few centimetres of insulation, in addition to the insulation that is placed between the rafters.

 

Insulation above the rafters

To keep the attic space as large as possible, especially when used for living, over the rafter insulation is often applied. 

High density boards are mounted onto the roof construction adding extra thermal performance and ensuring good fire and acoustic performance. It also services as the working layer to mount the external finish like rooftiles.

 

Our stone wool insulation ensures that both heat and sound are contained effectively. It also helps to:

  • Prevent heat loss
  • Improve energy efficiency overall
  • Increase fire safety
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, width should be considered to reduce waste material.

Should you wish to apply our rafter granulate, we recommend having this fitted by a professional installer with the right knowledge and equipment to do so.

Use our calculation tools to determine the energy efficiency savings roof rafter insulation can deliver. 

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Case studies

The State Hermitage, St Petersburg, Russia4

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
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17.2 MB

ROCKWOOL Red Book

An interactive specification guide for acoustic, fire and thermal insulation. ROCKWOOL will be regularly releasing new updates to ensure the content remains relevant and accurate, as well as evolving

To be updated
PDF
801.0 KB

FLEXI Installation Guide

To be updated
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397.6 KB

ROCKCLOSE Installation Guide

Financial support

Check the Energy Savings Trust website to see whether there are any additional financial support schemes available for roof rafter insulation.

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FAQs

FAQs

Should I insulate roof rafters?

When insulating the pitched part of the roof it is advised to insulate between the rafters first as that provides the most room for insulation without reducing the living area. Additionally, insulation can be placed below or above the rafter-line, depending on local requirements and the performance you are looking for.

What is the best insulation for a pitched roof?

In line with UK building traditions and legal requirements, we provide insulation solutions to match these specific needs. There is no one-size fits all solutions.

Can you have too much roof insulation?

The amount of insulation you apply should match with your needs, and the requirements and the design of the whole roof build-up.