The Christchurch Council has published thermal images of the Christchurch area. The colour keys are:
Blue: meaning the roof is cold. This may be the result of either the roof being very well insulated, which prevents heat from escaping, the house being substantially under heated or you were away when the image was taken and so the property was not being heated.
Predominantly green: This may be an indication of either well performing thermal insulation of the roof or a relatively low indoor air temperature (underheated house). It is recommended to check the quality of insulation where the colour is orange.
Yellow, some blue/green: less heat escapes through the roof but it is advisable to check for possible gaps in insulation where the roof colour is orange.
Predominantly yellow and orange: this is an indication of a relatively high roof temperature, which may be a result of either the indoor air temperature being high (overheated house), or insufficient roof insulation, or both.
Red: Property was either being used to grow cannabis in the roof area, expect a visit from the police in the next few days, property was on fire or the image was taken at 3:00 in the morning and it was the local BP station filled with thermo nuclear pies.
Remember: always blow on the pie.
Check out your property here: http://thermals.ccc.govt.nz
Thats real helpful stuff – wish Nelson City Council would look into something equivalent.