Thanks for the advice.
I have found following detailed instruction on procedures to check insulation with IR thermometer: Determining Insulation and Air Infiltration Levels Using an Infrared Thermometer
I have decided to buy a Black & Decker TLD100 Thermal Leak Detector, which seems to be an IR thermometer with some additional functionality to make finding hot / cold spots easier by coloring the aiming light dot. I will write here later my experiences.
After a week of using TLD100 I have to say my experience is mixed:
- it really works extremely well for its primary purpose, i.e. checking the house insulation
- using it to check heating system is a bit tricky, as IR thermometers do not work very well with reflective surfaces. In my case the heating pipes are from copper, which is quite shiny, and the insulation around them is a mineral wool finished with aluminium wrap, which is very shiny. Because of this, measuring their temperature with IR is very inaccurate, a contact thermometer would probably do a much better job. That said, the same limitations would apply for IR camera, as the principle is the same in both cases.