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Wall Insulation

Celotex offer a variety of high performance insulation products suitable for wall applications.

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The external walls of buildings come in many different forms of construction, so the way those walls are insulated varies dramatically too. Generally, the walls of existing buildings are probably either solid or cavity wall construction. A majority of new-build construction features masonry cavity walls, but timber frame, steel frame and solid wall construction may all be considered for a design.

What is cavity wall insulation?

The type of cavity wall insulation used and the way it is installed depends on the type of building project and the location of the building. Celotex only manufactures and supplies products suitable for use when constructing a new cavity wall.

For existing cavity walls with little or no insulation, ‘blown insulation’ products have been developed that are injected into the wall through the outer leaf masonry. As part of a wider building renovation and internal refurbishment, an option for boosting the performance of an already-insulated cavity wall is to fix thermally efficient rigid insulation boards (such as manufactured by Celotex) to the internal face of the walls.

This will take a few centimetres of floor space away, but is worth considering when looking for greater long-term energy savings.

Insulating timber framed and steel framed walls

Framed wall structures are lightweight, typically fast to erect, and offer variety in terms of external finish. Masonry is one option for a traditional appearance, but a range of cladding types are also possible. Timber frame has gained in popularity on projects aiming for a particularly low energy or sustainable end result.

Insulation is generally installed within the frame - but because the studs of the frame break the continuity of the insulation layer and reduce its performance, a second layer has to be installed over either the internal or external face of the frame. The choice depends on the building design, the thermal and airtightness performance required, and how service runs will be accommodated.

A rigid insulation board, such as Celotex GA4000, can be installed between timber frames. It can also be used as the internal wall lining or as an external sheathing layer.

Steel frame walls typically feature flexible insulation between the studs, often for better acoustics. Rigid insulation is fixed over either face of the steel frame.

Solid wall insulation - external and internal applications

A solid wall is perhaps best described as a masonry wall featuring no air cavities. It may be constructed from brick, blockwork or stone, and be anything from 100mm to 600mm (4 to 24 inches) thick depending on age, location and masonry type. Some variations of solid masonry walls may also be described as a single skin wall.

New-build projects featuring solid external wall construction are comparatively rare, such is the popularity of and familiarity with cavity walls. There are excellent arguments in favour of external wall insulation (EWI) fixed to the outside of a solid wall and finished in render, but it generally remains the preserve of low energy projects.

Similar EWI arrangements are possible on the outside of existing buildings and are a preferred option in terms of helping preserve long-standing building fabric. Keeping the masonry at the internal temperature of the building and protecting it from the elements can help prolong its life even further. However, EWI is not necessarily always a practical arrangement

An EWI arrangement featuring Celotex insulation products and timber battens is detailed here.

Just as insulation can be applied to the exterior of a solid wall, so it can be applied internally. Internal wall insulation (IWI) is not a sensible option for new-build projects, but is a common solution for treating existing buildings. Insulated plasterboard products can be used in a variety of internal lining applications, including walls.

Refurbishing or renovating an existing wall and improving its thermal performance from the inside needs to be done with care. The moisture content of an un-insulated solid wall depends on the sort of weather it is exposed to and the humidity inside the building. Applying insulation to the wall can change the delicate balance, and we recommend contacting the Celotex technical team for further advice.


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