Installing double-glazing can save you up to 20% of your fuel bill. It also reduces noise coming in from outside. Secondary double glazing – fitted in addition to your existing windows, is cheaper, but less effective. This is because it is the air gap that provides the insulation, not the extra layer of glass, and this is more effective in a double glazing unit.

You should be given a choice of PVC (PVC-u), aluminium or wood frames. Although PVC often lasts longer (although so long as you paint your wooden frames regularly they should last just as well) it is a poor environmental option. Aluminium manufacturing is also very energy intensive. Wood may be more expensive, particularly hardwood. You can reduce wood costs by specifying that hardwood should only be used for the sill and bottom pieces, which are more liable to rot. Make sure any hardwood used is from sustainable sources.

A low-emissivity coating on the inside of the unit helps reduce heat-loss back out through the glass.

Before you fit primary or secondary glazing, consider your escape routes in case of fire – don’t seal them off.

Always ask for recommendations from friends and colleagues when choosing a double-glazing company.

ever thought about cleaning your windows with vinegar?