Civil Engineering Reference
In-Depth Information
Element
U-value (W/m
2
K
)
Walls
0.30
Floors
0.22
Flat roof with integral insulation
0.20
Pitched roof with insulation at ceiling level
0.16
Pitched roof with insulation between rafters
0.20
Windows, roof windows and roof lights
1.80
Doors with more than 50% of internal surface area glazed
2.20
Other doors
3.00
Straw bales have a U-value of between
0.13 and 0.20, depending on the quality of
the bales used and the degree of skill used
in installing them. This doesn't include
the render or plaster on either side, which
would lower the U-value beyond this.
The high insulation value of straw is
achieved because of the width of the bales.
Compare the U-values of other common
wall building materials, shown in the table
below.
Material
U-value (W/m
2
K)
105mm brickwork, 75mm mineral fibre, 100mm light concrete block,
13mm lightweight plaster
0.33
0.40
100mm heavyweight concrete block, 75mm mineral fibre, 100mm
heavyweight concrete block, 13mm lightweight plaster
100mm lightweight concrete block, 75mm mineral fibre, 100mm
lightweight concrete block, 13mm lightweight plaster
0.29
Source: Chartered Institute of Building Services Engineers (2002) 'Thermal Properties of Building
Structures' in
Guide A: Environmental design
.
