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Windows provide the primary sources of light and ventilation and have a major impact on the appearance of a dwelling. Your choice of windows is therefore one of the key decisions you will make when building for yourself. Windows come in many shapes and styles but there are really only four main choices of materials for new homes - softwood, hardwood, PVCu and aluminium. Bespoke design There are any number suppliers that sell standard ranges of windows from catalogues. The quality of some is questionable but there are some excellent manufacturers - certainly the ones we deal with. There is obviously a limit on the sizes and styles available and with the trend in self build very much towards bespoke design and higher levels of specification, more and more of our clients are opting for purpose made windows. These allow the designer to incorporate any size, shape or style of windows (subject to planning conditions of course) free from the limitations of standard modules. More so since there is growing demand for large areas of glass in today's housing.  Softwood Class 1 redwood is generally recognised as the material that provides the best quality softwood windows. Regions such as Scandinavia, where few hardwoods grow naturally, pioneered the use of this material. Alongside this was the development of sophisticated micro-porous stains and paints, the former allowing softwood windows to have the appearance of hardwood. The softwood windows we provide also carry a 30-year guarantee against fungicidal rot. If you do choose softwood windows (or it may be a condition of your planning consent) then laminated timber is generally recognised as a cut above standard softwood. It does cost more but it provides a more stable frame, is free of knots and you achieve a better quality finish. Because of the lack of knots laminated timber is very suitable for staining. Hardwood
Natural oak has now replaced mahogany as the most popular hardwood not just for windows but also internal features such as stairs and doors. This comes from managed/farmed sources where replacement programmes are well in place. All my clients would probably opt for natural oak widows but for one important factor - they cost around 3 times more! So many are naturally put off by the extra cost. PVCu This material has also suffered from a bad press due to early problems with 'yellowing' and the sheer bulk of the frames. These drawbacks have now been resolved and the windows we supply carry a 20-year guarantee against discolouration. Improvements in manufacturing techniques (reinforced sections) now allow PVCu widow sections to be much slimmer and therefore look virtually identical to timber. In recent years manufacturers have also made significant strides with woodgrain finishes and these now look remarkably close to the real thing. As regards cost, if you compare white PVCu casement style with the better quality softwood windows (such as the ones we supply) then the difference is negligible. However when you factor in the cost of decorating and on-going maintenance then PVCu is in real terms more economical. Woodgrain finish externally (e.g. oak) with white finish internally adds circa 20% to cost (making it about the same as laminated softwood) and for another 5% you can have woodgrain both sides. Aluminium
The most common use of this material is in conjunction with traditional stone window surrounds (often seen in locations such as the Cotswolds National Park) and where the stone surrounds are themselves one of the main architectural features. In this situation the heavier section of timber or PVCu frames would detract from the aesthetics of the building as a whole. Roof lights are also available in aluminium. The aluminium is either anodised or heat coated in durable polyester paint. As regards colour the sky is the limit. White, brown, green, bronze and black are all commonly used, which is one of the reasons aluminium frames are often chosen for modern commercial buildings. Cost is a certainly a factor though with aluminium typically costing twice as much as softwood frames. 
Glazing bars Glazing bars can enhance the appearance your windows and in certain cases e.g. Georgian style they are a pre-requisite. Manufacturers use three main methods of incorporating glazing bars. Firstly the bars can be sandwiched between the two layers of glass. Secondly fret frames can be face fixed to the glass (both inside and out) and lastly where the bars are an integral part of the window. The latter is probably the most authentic but please bear in mind that each small double glazed unit has to be individually manufactured then fitted, which adds significantly to the cost of the window. The cost of long term maintenance is also a consideration with for example, timber Georgian windows. Security Window locks and trickle ventilators are now part of the regulations. This allows fresh air into the room whilst the opening sash of the window remains closed and locked. Some years ago there was a security scare with PVCu windows in that the whole glass pane could be removed by prizing off the glazing beads. These days it is an NHBC requirement that they are internally glazed. Additional security features can be added to windows such as espagnolette locking and shoot bolts. On a house of 200 m² this would typically cost circa £1,000 (or around £500 for the ground floor only) which is not a huge amount in the overall scheme of things. Another security/safety option is toughened glass although there are a number of locations in a dwelling where the Building Regulations stipulate toughened glass as standard e.g. French doors. 
Heat Loss Under the Building Regulations all windows must be double-glazed with energy efficient thermal glass (commonly referred to as 'k-glass'). The 'U' value of your windows can be further improved by filling the cavity between the two panes of glass with argon gas, which increases thermal efficiency and therefore reduces heat loss. We provide this as standard. Special features Manual glazing on site can lead to problems with a breakdown of the sealed units and subsequent loss of guarantee. So we provide your windows factory glazed as standard with a 10-year warranty on 'misting'. There are lots of special feature available to you: glass can be provided tinted, self-cleaning, leaded, sound reducing ('whisper' glass) and even with blinds built in to the glazing cavity. Another option is triple glazing. It is also an expensive way of improving thermal and sound performance because the manufacturing process costs significantly more than for double glazing and the window frames would need to be specially made to take the wider glass units.
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Our Materials Manager, Dan Mutti discusses the important subject of windows. Dan has been with the company for the best part
of two decades and has a wealth of knowledge of materials for individual homes. His advice and expertise are freely available
to all our clients.
As good as these stains are there is nothing quite like the 'look' and 'feel' of real hardwood. Mahogany was
popular in the eighties and nineties but fell out of favour for two reasons. Firstly it is essentially a dark
coloured timber and people are now looking for a lighter finish. Secondly there was a lot of bad publicity
regarding the impact on the environment of the indiscriminate clearance of large tracts of rain forest.
Aluminium has until recently been used mainly in commercial buildings or for patio doors in housing but windows made from
this material are gaining in popularity in domestic housing. It is light and inherently strong, which allows the frames
and glazing bars to be of a thinner section than the other options. It lasts a lifetime and is maintenance free.