Chimney leak or interstitial condensation

Hi all, bit of help needed please.

I am a roofer (Cornwall, England) and look at a lot of leaks. Sometimes I will go to a house and the owner will say he has a chimney leak, he has had the flashings changed for loads of money, that hasnt worked so he has had it rendered for loads of money, that hasnt worked - what can I do? I know that the chimney breast as it comes into the house from the cold exterior, will be a solid mass of coldness (where I am from these are often large granite chimney stacks and solid walls). Usually these stacks are plastered or rendered as they come into the house. I know that the surface under the plaster will be very cold, but if I use an IR thermometer laser to test the surface of the wall, often it will be pretty much at room temperature, especially if its plaster on plasterboard. I need to know the temperature behind the front facade of the plaster, on the wall to see if humidity is getting through the plaster, comdensing on the cold granite and causing damp spots on the wall.

So, my question is, will a Thermal Image Camera shot of the wall show up the coldness behind the facade of plaster, or will it just show the surface of the plaster wall? If the latter it would be a waste of time. If however it will show the cold behind the plaster then I will know that condensation will be forming on the cold wall and causing the damp spots on the plaster.

This would mean the acquisition of a thermal camera will be worthwhile. If so, I have seen a Flir E40 which will probably go for around £2000, or a fluke Ti20 which will probably go for around £1200.00. If anybody could steer me towards one of these, knowing the sort of thing I would be using it for - I would be very greatful! Obvioulsy if you think I would be wasting my time as a TI camera will not show a surface temp behind a plastered wall, then you could be saving me a handful of cash:mrgreen:.


Here in the states at least, one can rent the equipment by the day. You could try it out and come to your own conclusion as to the value.