BUILDING PERFORMANCE INSULATION 250
Measured heat loss Predicted heat loss
200
150
100
50
0
Dwellings
Figure 1: A summary of the results of heat-loss monitoring data from the Elm Tree Mews Field trial, carried out by the Centre for the Built Environment at Leeds Metropolitan University, on behalf of the Joseph Rowntree Foundation and Joseph Rowntree Housing Trust.
www.lmu.ac.uk/as/cebe
task should be undertaken by a member of the design team who understands the complexities of insulation performance. In general, a conservative approach is recommended, as changes during design development or construction rarely improve performance. Particular care is needed when scrutinising insulation conductivities.
250 Ventlation 200 Infiltration
Thermal Bridges Doors
150 Wall Heating, 208 100 Floor
Manufacturers are improving their products, but specifiers need to be somewhat sceptical about their claims. Insulation materials should always refer to the λ90/90 value, which ensures that a conservative figure is used and on-going sampling is in place to ensure quality. If in any doubt, take a conservative value from CIBSE Guide A: Environmental Design.
50 Roof Windows 0 Losses
Internal Solar
Gains A typical heating balance for a house built in the early 1980s
45 40 35 30 25 20 15 10 5
0 Losses Gains
A typical heating balance for a low energy house
Figure 2: Comparison of thermal losses and gains in older and newer homes. The left-hand bars represent annual heat losses – heat conduction through fabric such as windows, roof and walls, as well as heat loss due to bulk air transfer via infiltration and ventilation. The right-hand bars show the solar and internal heat gains, with the heating in yellow representing the difference between the losses and gains
www.cibsejournal.com November 2011 CIBSE Journal 35
Ventlation Infiltration
Thermal Bridges Doors Wall
Floor Roof Internal Heating, 19
Windows
Solar
KWh/m2.yr
Dwelling heat loss (W/K)
KWh/m2.yr
House 9 House 3 House 4 House 2 House 1 House 6 House 8 House 5 House 16 House 7 House 14 House 15 House 12 House 13 House 11 House 10
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