See our expert buyer's guide to replacement windows
Materials and finishes
■ Timber frames are suitable for homes from Georgian rectories to suburban semis. The particular benefit of wood is that it can be easily patched and repaired, and upgraded for draught proofing.
■ Bronze casements are made from manganese brass alloy known as architectural bronze. The strong yet slim frames will easily accommodate panes with the latest thermal and security technology.
■ Mild steel window frames are extremely strong and lend themselves to ultra-slim frames. Ideal for windows with large panes of glass, they don’t rust and, as they are powder coated, don’t need repainting.
■ Aluminium windows, usually featuring slightly wider frames than steel, refuse to rust and similarly require minimal maintenance, but are lighter than steel. Can be reinforced for extra durability with steel corner sections.
■ uPVC (unplasticised polyvinyl chloride) can be less attractive and it can discolour, but metal and wood-effect finishes are now available and the thermal efficiency of the best examples is impressive.
Options range from reclaimed to modern float glass, and single glazing to triple-glazed units. You can specify toughened safety glass or laminated security glass, as well as self-cleaning, solar control, decorative and glazing with varying cavities – from slender profile for listed buildings to over 25mm deep. There is also extra-low-emissivity glass, such as Pilkington K, with a coating on one pane that increases its thermal properties. For energy efficiency, argon-filled units are popular.