We shall use the case of tempering Low-E glass for the purpose of describing the application of convection in a demanding process for a product growing in popularity. Before the 90’s, furnaces were mostly designed for the tempering of clear glass. For this reason, the main focus at the time was on even application of radiation heating in the furnace. This was quite understandable, because clear glass has high emissivity and it absorbs heat very well. When the new low-emissivity glass products hit the market at the end of the 80’s and early 90’s, great difficulties in tempering of this kind of glass were initially experienced.