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416 Barry’s Advanced Construction of Buildings
Table 7.1 Comparison of insulation materials used within cladding systems
Product
Properties
Approximate thickness
to achieve a U-value of
0.2 W/m 2 K (dependent
on construction – for
comparison only) (mm)
W/mK Thermal
conductivity
Cellulose fibre
Insulants used for
175–230 ≈0.035–0.045
construction where
space is not a premium
Glass wool fibre In combination with rigid
160–220 ≈0.031–0.044
insulants can reduce
thermal bypass – with
acoustic properties
– economic solution
where space is not a
premium
Rook wool fibre In combination with rigid
155–250 ≈0.034–0.042
insulants can reduce
thermal bypass – with
acoustic properties;
economic solution
where space is not a
premium
Expanded polystyrene Rigid insulation – reduced 140–170 ≈0.031–0.038
thermal conductivity
Extruded polystyrene Rigid insulation – reduced 130–190 ≈0.029–0.039
foam
thermal conductivity
Polyurethane foam Mid-range insulants 160–180 ≈0.034–0.036
with CO 2
Polyurethane foam
110–150 ≈0.022–0.030
with Pentance
Phenolic foam 120–130 ≈0.024–0.026
Polyisocyanurate foam 110–120 ≈0.022–0.024
Phenolic foam with Upper mid-range
80–120 ≈0.017–0.022
foil face
insulants
Polisocyanurate foam
80–90 ≈0.018
with foil face
Aerogel blanket High-performing insulants
60–70 ≈0.010
– advanced cladding;
relatively high costs
Vacuum insulation High-performing insulants
– advanced cladding;
relatively high costs
25 ≈0.005
through the ducts may cause an unacceptable level of noise, and the air handling system
is costly to install, maintain and run. To economise, it is usual practice to install individual
air-conditioning heaters, which filter, dry and heat air that is recirculated from individual
rooms with the effect that stale air is constantly circulated, so causing conditions of
discomfort.
As an alternative, buildings may be constructed and finished with mainly open plan floor
areas largely free of enclosed spaces, set around one or more central areas open from