Recently we have had an increase in the number of variations raised against Approved Document L due to glass units made incorrectly.
When the inspector visits the installation one of the tests he will conduct is looking for low e glass. Actually, if you watch him closely he is completing two tests. The first is the one where he holds the low e detector flat to the glass and presses a button. If it beeps and the light turns green low e is present.
Next he will flip the detector forwards and touch the two little metal prongs on the glass. Hopefully nothing will happen. If he does get a beep it means the low e coating is exposed to the air – and that isn’t good!
The low e coating is a very thin layer of metal and when the two prongs touch it a circuit is made and the detector indicates a problem.
Now as installers it isn’t easy for you to spot this without a detector. However, it will become noticeable fairly quickly if you use a soft coat low e product as these break down over time and a silvery mark that looks a bit like a water stain will appear.
If you do have units like this on one of your jobs give your glass supplier a call. I’m sure they will be more than willing to sort it out for you.