Walls

Externally insulated solid walls

Solid masonry walls may be insulated on their external surface and the insulation covered by an external finish such as render, boarding or tiling (see figure 2). That construction offers numerous benefits:

• all the thermal mass of the wall lies within the insulation envelope, resulting in a structure with a slow thermal response which is well suited to continuously heated buildings;
• solid walls do not require vented cavities to drain away moisture, which eliminates one route for air infiltration, making it easier to construct buildings with low rates of air permeability;
• detailing of windows and doors is easier as there is only one structural plane to consider within the wall;
• large format blocks and thin joint systems speed construction and reduce the effect of thermal bridging.

Internally insulated walls

Walls may be insulated on their internal face, with the insulation applied between the structure and the internal finish. Installing the insulation in that way will mean the thermal mass of the wall is outside the insulation, resulting in a rapid thermal response, suitable for buildings which are intermittently heated.

Internally insulating walls is a useful solution for upgrading the thermal performance of walls in the course of projects which require consequential improvements. It will not affect the external appearance of the building.

Timber or steel framed walls

In framed wall constructions of timber or steel the insulation is fitted between the studs, combining the structure and thermal insulation into the same plane. The internal face of the wall is lined with plasterboard, whilst the external face can be finished with a single leaf of brick, tile hanging, boarding or a render system. Where necessary the thermal performance of the wall can be improved by installing a further layer of insulation across the face of the studs: that will also reduce the effects of thermal bridging.

The use of framed wall construction has become increasingly common, most notably in the Republic of Ireland and Scotland where the required U-values for walls are already as low as 0.27W/m²K and 0.30W/m²K respectively.

STYROFOAM Solutions

The STYROFOAM™ solution for the external and internal insulation of walls is STYROFOAM LB -X  which has been designed to give the maximum benefit in wall construction:

• the strong, rigid boards are self-supporting
• low water absorption means performance is unaffected by moisture

For the full physical properties and performance characteristics of STYROFOAM LB-X see under Product Data.

Table 01 STYROFOAM thickness (mm) to achieve U-values (W/m²K)

	U-value	0.25	0.28	0.30	0.35
Solid - internal insulation
		110	90	80	70
Timber frame - insulation between and external to studding
Stud depth
90mm		90+30	90+25	90+25	90
140mm		140+25	140	140	140