Use this one page guide as the basis for your specifying timber windows.
There are many hundreds of wood window manufacturers selling in the UK. Today's windows and doors are engineered to perform and to last a lifetime with only minimum maintenance. You need to be confident that the windows you specify will meet the high quality, performance and sustainability standards you expect. The simplest way is to specify windows manufactured by a Wood Window Alliance member.
As a condition of membership, manufacturers meet audited quality, performance, and sustainability criteria. Membership and performance auditing are reviewed regularly. Windows are: fully factory finished and glazed; CE marked, supported by Certificates of Conformity; supported by warranties covering glazing, ironmongery, and coatings endorsed by accredited WWA suppliers; and fitted by qualified installers.