Double glazing slows down heat loss in the house through conduction. It does this by having either an air gap or vacuum between two panes of glass.
Loft insulation is very important for slowing thermal energy loss in the home as all the heat in the air of the house rises to the roof via convection currents, so slowing down conduction out of the roof is very important to stop heat travelling to the roof and escaping the house.
Having thicker, more insulative bricks slows conduction out of the house - reducing the waste from heating your home.
Cavity wall insulation replaces the air gap between the sets of bricks in your walls. The foam that is pumped into the cavity traps the air, and is more insulative than the air by itself.
The higher the tog rating of a duvet, the more insulative it is, so in winter a higher tog can keep you warm at night.
Solar panels get energy from the sun and convert it into electricity for the home from the silicone within them. This energy is free due to being taken from the sun, so can further help save money on heating and reduce the need for fossil fuels to make electricity, but use something cleaner.