This package provides a comprehensive thermal insulation of a building and includes the following components:

• Roof insulation, using either an insulation panel/roll or a spray foam under the roof. External roof insulation is also possible (i.e. built-up roof insulation under waterproofing)
• Energy efficient windows (double or triple glazing)
• Floor insulation
• Wall insulation, external (for instance with External Thermal Insulation Composite System – ETICS) or internal

Roof / loft insulation

Materials

Different types of materials can be used for internal and external insulation, either in a roll, panel or spray foam form, each having its own benefits and limitations: wool (glass, rock, sheep or hemp), polyurethane, expanded polystyrene (EPS) or extruded polystyrene (XPS).  The recommended uses are the following:

Techniques

There are two main ways to insulate a loft or a roof: at the joists or at the rafters.

Insulation at the joists (Source: ADEME)

Cold loft insulation at the joists

The insulating material is laid (or sprayed) on the floor of the cold loft.

Warm loft insulation at rafter or externally

For the insulation of warm and occupied lofts under a pitched roof, two techniques are available:

Internal insulation

The internal insulation can be done with semi-rigid panels or rolls, whose layout will depend on the structure of the building frame and the available space. A loose-fill insulation can also be injected in an air-tight cavity under the roof cover.

Loose fill insulation (Source: ADEME)

Insulation at the rafters with panels (Source: ADEME)

External insulation

Insulating from the outside avoid loosing living space but requires to remove the existing covering. Load-bearing panels can be used, or insulation can be added between the rafters and the roof covering, with a roof sarking (i.e. a protective and waterproof second skin under the roof). This last solution requires raising the roof line.

Flat roofs insulation

For flat roof, external insulation (“hot roof”) is recommended. Insulating from the inside can cause damage as it will inevitably lead to the formation of condensation. In this case, a rigid insulation is fitted outside, above the existing weatherproofing. This is then covered with a further weatherproofing layer.

External wall insulation

External insulation allows to insulate and restore the façade at the same time. Thermal bridges are usually easier to address this way, and the living are is not reduced as in the case of internal insulation. It also reduces the disturbance to the occupants. However this technique is usually more costly than internal insulation, and may require a building permit.Thermal bridges around the balconies should also be carefully addressed.

Techniques

External Thermal Insulation Systems (ETICS) can be applied in two ways:

External wall protected by coating (Source: ADEME)

External wall insulation protected by cladding (Source: ADEME)

• insulating materials (glued or screwed to the wall) protected by coating
• Insulating materials protected by cladding. In that case the insulating panels are installed on a frame fixed to the wall. An air gap is maintained between the external cladding and the insulation

The application of ETICS ensures a continuous thermally insulated envelope, however the big number (~10/m²) of fasteners crossing the insulation (if this technique is used) can raise an issue of thermal bridging, unless thermally decoupled fasteners are used.

Reduction of thermal bridges in concrete balconies

The slab acts as thermal bridge, which results in heat losses and potential formation of condensation and mould. The balcony can be cut-out to remove this bridge. The slab can be partially cut – in which case thermal breaks are inserted between the balcony and the wall, or completely cut which requires the creation of a self-bearing structure.

Energy-efficient windows

Materials

The performance of the windows depends on the glazing and the frame. The level of performance is expressed by the thermal transmittance coefficient Uw. Performant solutions exist with timber, PVC or aluminium (with thermal breaks) frames.

Double glazing

Double glazing is made of two glass layers separated by an air gap. It is more performant than simple glazing and reduces the condensation and heat losses through the windows. The new generation of double glazing includes argon instead of air, as well as a fine transparent layer with low emissivity, usually silver-based: its insulating capacity is 2 to 3 times that of standard double glazing.

Triple glazing

Triple-glazing is made of three layers of glass separated by two layers of argon or krypton and two low-emissivity metallic layers. The Uw value is excellent, however the ligh transmittance can be lower than for a good double-glazing.

Techniques

Windows can be changed with two main techniques:

• By keeping the existing frame: this a simplest option, however the performance and the glazed area are slightly reduced
• By removing the existing frame: this is the most performant option, however it requires more work and some finishing

As double or triple-glazed windows will be more airtight than the original single-glazed frames, condensation can build up in the building due to the reduced ventilation. If there is not a sufficient level of background ventilation in the room, replacement windows should therefore have trickle vents incorporated into the frame, that let in a small amount of controlled ventilation.