Renewable Energy, you should be able to explain heat energy flow through the materials in buildings, especially windows.
a.State the three main mechanisms for heat transfer through a window, and briefly indicate how the heat energy is transferred through a window in each case.

b.Original double-glazing designs simply featured an air gap between the two panes of glass. Since 2013 the minimum acceptable UK Windows Energy Rating for new and replacement windows (on a scale of A to G, with A being the best) is C. Argon filled units with a gap between 12 and 16 mm are able to achieve this. However, this is a potential problem for historic buildings.

Explain, with reference to the gap dimension and the properties of the contents of the gap, how glazing units with acceptable UK window regulation U-values may be achieved.