Secondary Glazing creates a barrier that minimizes the transfer of heat energy from one material to another by reducing the conduction, convection and/or radiation effects, in other words making it harder for the heat to escape your home.
It is done by reducing conduction, convection and/or radiation effects. The R-value is a standard of measurement of this insulation.
Most insulation is used to prevent the conduction of heat. In some cases radiation is a factor. A good insulator is obviously a poor conductor.
Less dense materials are better insulators. The denser the material, the closer its atoms are together. That means the transfer of energy of one atom to the next is more effective. Thus, gases insulate better than liquids, which in turn insulate better than solids.
An interesting fact is that poor conductors of electricity are also poor heat conductors. Wood is a much better insulator than copper. The reason is that metals that conduct electricity allow free electrons to roam through the material. This enhances the transfer of energy from one area to another in the metal. Without this ability, the material--like wood--does not conduct heat well.
The design goal is to keep the surface temperature above the dew-point temperature of the surrounding air. Calculating surface temperature is relatively simple, but selection of the appropriate design conditions is often confusing. The appropriate design condition is normally the "worst case" condition expected for the application. For condensation control, however, a design that satisfies the worst case condition is sometimes impossible