Not sure if this will help but ill try. The acurite measures ambient air temperatures while the temp gun measures surface temperatures. The temp gun should be used to measure the temp of the animal,heat source ect..The temp gun wont give you an ambient air temp that will match what your accurate reads. I think the glass will be colder than what the acurite reads being placed next to the glass. I have been doing a little temp gun research but I still wonder if I will also have this problem when the temp gun arrives. Please don't take what I wrote to the bank! I could be 100% wrong and I hope someone else can post to clear up your situation. --Josh