In the Netherlands, insulated glass is rated by a standardized rating system, classifying it into 3 categories by the u-value:
- HR : U value between 2.0 and 1.7
- HR+ : U value between 1.6 and 1.3
- HR++ : U value less than 1.2
The price difference between these types of insulated glass is quite large. After the glass has been installed, is there any simple way to measure the U value or otherwise check the type? I guess it would be quite easy for a swindling contractor to sell HR++ and install HR without it ever being noticed?