283757893275

Cladding and Curtain Wall Construction 417
Silicone sealant
Edge spacer
Vacuum insulated panel
(microporous fumed silica,
contained in metallised plastic
film where air has been drawn out)
Tinted and coloured glazing (face
finish is optional)
Internal glazing or cladding material
Figure 7.1 Glazed vacuum insulated cladding panel.
ground to roof level to provide facility for the natural movement of heated air to rise and
so cause natural ventilation. This stack system of ventilation, so called by reference to
the upward movement of air up a chimney stack, can be utilised by itself or with some
small mechanical ventilation to provide comfort conditions with the least initial and
running costs.
Thermal bridge
The members of a structural frame can act as a thermal bridge where the wall is built up
to or between the frame, as illustrated later in Figure 7.2, where the resistance to the thermal
transfer through the brick slips and beam is appreciably less than through the rest of the
wall. Similarly, there is a thermal bridge across a precast wall panel and a beam and column,
as illustrated later in Figure 7.3. It may be difficult to provide an effective way of preventing
the thermal bridge formed by the supporting structural frame. The effect of the bridge may
be modified by the use of floor insulation and a suspended ceiling or by setting frame
members, where possible, back from the outer face of the wall, as illustrated later in Figure
7.4. Wall panels of precast concrete, GRP and glass fibre reinforced cement (GRC) have
been used with a sandwich or inner lining of an insulating material. This arrangement is
not entirely effective because the insulating material, if open pored as are many insulating
materials, may absorb condensate water, which will reduce its thermal properties, and the
edge finish to panels, necessary for rigidity and jointing, will act as a thermal bridge. Thin
metal wall panel materials or composite panels, which are supported by a metal carrier
system fixed across the face of the structural frame, can provide thermal insulation more