Anyone wishing to insulate a pitched roof should not just consider the thickness of the insulation. The key factors are how the entire roof structure works and the building’s specific circumstances. In practice, the question often arises as to which solution is best suited: above-rafter insulation, between-rafter insulation, under-rafter insulation or a combination of several layers.

There is no one-size-fits-all answer. Which option makes sense depends on the condition of the roof, the planned work, the desired level of thermal insulation and the structural possibilities. That is precisely why it is worth carrying out a thorough assessment when it comes to insulating a pitched roof.

Why roof insulation is so important for pitched roofs

Anyone wishing to insulate a pitched roof should bear in mind that this part of the building has a significant impact on energy consumption and on the indoor climate directly beneath the roof. If the thermal insulation is inadequate, a great deal of heat is lost in winter. In summer, the loft can heat up much more quickly.

Insulating a pitched roof therefore not only improves winter Thermal insulation. Issues such as airtightness, moisture protection and summer performance must also be taken into account during construction. It is therefore not just the insulation itself that is crucial, but how the individual layers of the roof interact.

Between-rafter and above-rafter insulation: ideal for comprehensive roof renovations from the outside

Above-rafter insulation is installed above the rafters and forms a continuous layer of insulation. It is particularly worthwhile if the roof covering is due to be replaced anyway or if a comprehensive renovation is planned.

The main advantage lies in the continuous thermal insulation. As the insulation is situated above the load-bearing structure, thermal bridges in the area of the rafters can be significantly reduced. At the same time, the structure often remains visible inside the building, if this is desired for architectural reasons.

This solution is more complex in terms of construction, as the roof has to be opened from the outside. However, in the case of a complete refurbishment, it is often the most technically sound option, as it allows for a very neat installation with a clear separation of the layers.

Between-rafter insulation: tried and tested and flexible

If building owners or planners wish to insulate a pitched roof, the Insulation between rafters one of the most important options being considered. Between-rafter insulation is installed between the rafters and is one of the most common solutions for pitched roofs. It is particularly useful when the roof structure is easily accessible from the inside or when an attic is to be made more energy-efficient.

In practice, particularly with existing structures, it is clear that rafter spacing, unevenness and joints are rarely entirely ideal. This is why adaptable insulation materials are required.

This is where SAGLAN glass wool insulation really comes into its own. The material can be flexibly integrated into the roof structure, adapts well to existing conditions and is particularly suitable for situations where clean and reliable insulation is required between the rafters.

It is important to ensure that it is not just the roof spaces that are filled. Air-tightness, moisture protection and integration into the overall roof structure must also be properly addressed.

In many cases, under-rafter insulation is not a stand-alone solution, but rather a supplementary measure. It helps in situations where the existing rafter depth is insufficient to achieve the desired level of thermal insulation between the rafters alone.

Insulation between and beneath the rafters: often the most practical combination

Particularly in renovation projects, combining insulation between the rafters and below them is often a sensible approach. First, the existing space between the rafters is utilised; then, an additional layer of insulation is added below the rafters.

This solution is particularly useful when:

• the existing rafter height is limited
• the roof should not be opened from the outside
• thermal insulation still needs to be significantly improved

In practice, this is often a sensible solution from both a technical and economic point of view, as it allows the existing structure to continue to be used whilst creating an additional layer of insulation.

Under-rafter insulation: adding insulation from the inside

Under-rafter insulation is installed on the interior side, beneath the rafters. It is particularly suitable when the roof cladding is intact and is not to be opened, but thermal insulation needs to be improved.

The advantage is that the work can be carried out from the inside. At the same time, it is important to bear in mind that an additional level is being built into the interior, which means that headroom is lost.

Which solution is appropriate and when

The right insulation solution for a pitched roof always depends on the specific project.

Insulation between the rafters and on top of the rafters is particularly useful when:

• the roof covering is being replaced anyway
• where continuous thermal insulation is required
• Thermal bridges in the area of the rafters should be minimised as far as possible

Insulation installed between the rafters is particularly suitable when:

• the structure is easily accessible from the inside
• the loft is to be made more energy-efficient
• a versatile insulation material is required

A combination of between-rafter and under-rafter insulation is a good option if:

• the rafter height alone is not sufficient
• where the thermal insulation needs to be improved without completely replacing the roof from the outside
• a workable solution is being sought for the refurbishment

Insulation installed beneath the rafters is particularly worthwhile if:

• the roof should not be opened from the outside
• the thermal insulation needs to be improved from the inside
• it is structurally possible to incorporate an additional layer of insulation

What is often underestimated when it comes to refurbishment

In practice, when it comes to insulating pitched roofs, the focus is often primarily on the thickness of the insulation. However, the connections, transitions and sequence of layers are at least as important. With pitched roofs in particular, the quality of the solution is often determined not by the large surface area, but by details such as:

• Connections to the gable or eaves
• Penetrations and fittings
• Transitions to roof windows
• Air tightness on the warm side
• Moisture protection throughout the structure

A pitched roof is therefore not properly renovated simply by installing more insulation. The crucial factor is that the entire structure functions correctly from a technical point of view.

What this means for SAGER

At SAGER, we consider roof insulation not just in terms of individual materials, but in terms of the entire structure. Particularly when it comes to Insulating a pitched roof It is important that thermal insulation, damp-proofing, airtightness and summer performance are all well-balanced.

With SAGLAN glass wool insulation, SAGER offers solutions that are particularly well suited to situations where flexible and adaptable insulation materials are required in roof structures. Glass wool is particularly well suited to intermediate or combined intermediate and under-rafter insulation, where it can fully demonstrate its strengths in terms of ease of installation and thermal insulation.

However, the specific circumstances are always the decisive factor. That is why it is worth opting for a solution that considers not just the insulation itself, but the pitched roof as a complete system.

Conclusion

There are various ways in which it can be beneficial to insulate a pitched roof. Whether it is above-rafter, between-rafter or under-rafter insulation, or a combination of these: the right solution depends on the existing structure, the planned work and the requirements for the installation.

It is crucial that the insulation solution is technically suited to the building and works effectively within the entire roof structure.