Fibre glass is used as loft insulation as it reduces the rate of energy transfer by conduction.
Double glazing has 2 glass panes with dry air after its been vacuumed. The vacuum is a good insulator as their is no particles for the heat to travel across.
Solar Panels provide insulation without having to expense for 2 extra sources of heat that aren't sustainable. Solar panels absorb infrared radiation from the Sun which , electrically, transfers into useable energy.