The Self Build Self Help Site window design
Sub header photo of a window
The key decisions you will make at first are for the material and the design. You will also need to consider the external window cills - the design of these may, to some extent, be dependent on the colour of the window frames. You will probably get quotes from a number of companies so what else do you need to look out for with modern windows?

The notes on these pages will give a good outline of the key design decisions you will need to make. Also, refer to the web site WindowInfo.co.uk which is a must have guide if you are buying double glazing, replacement windows, uPVC sash windows, uPVC doors or porches and more.

Your architect will stipulate "K" glass and probably Argon filled double glazed units. K glass has a low emissivity coating on the outside surface of the inner sheet of glass. This reflects heat from inside the room back into the room, rather than letting it radiate across the gap. Argon is much less heat conducting than air. The K Glass and Argon will help meet the building regulations requirement for the thermal calculations.

Wood, uPVC or Aluminium?

Firstly the material - these days usually a decision between uPVC and wood, although aluminium windows are available. A few Planning Departments will stipulate the material, for example Pembrokeshire Coast National Parks authority stipulate wooden frames, at least for those houses in their jurisdiction that are in prominent positions. This requirement is not universally welcomed as many people require "low maintenance" uPVC. And indeed, once the house has been completed and the Completion Certificate obtained, the owner can change the windows to uPVC (although an expensive and messy process).

If you like a wooden finish then wood effect uPVC is actually a very good alternative, common colours being pine, oak and mahogany.

Aluminium windows are not quite so popular but have the advantage of having slimmer frames than uPVC. They are, however more expensive than uPVC and wood. Aluminium frames can be installed within a wooden frame (see picture on next page) which gives the warm wood effect with the strength and slimmer profile of the aluminium frame itself.

Another aluminium option is for wooden windows clad with aluminium - Rationel Windows is one such manufacturer.

Perhaps the next decision - what colour? If wood then most manufacturers will supply windows/doors already painted or stained as a natural finnish.

A coloured finish (often uPVC in mahogany and cherry oak wood grain styles) may be more expensive than white. You can get different finishes for outside and inside - a common one is wood effect outside and white inside.

With regard to uPVC, many suppliers use one of a few standard profiles, a common one being that shown in the picture below on the right. A favourite finish of the author of this page is to have an ogee profile on the outside as well as the inside (picture below on the left). This external profile is not often seen - we're not quite sure why (the cost used to be significantly more than a plain external profile but this is not necessarily the case now - check with your window supplier).

Diagram of structure of soffit
Ogee profile

(externally beaded)

(Click on pictures for a larger view)

Photo os soffit
A common plain profile

(internally beaded)