A rated window

When choosing windows the two main considerations are normally performance and security. Window performance is usually measured by counting the U-value and energy rating.


This measures the rate of heat transfer and the value stated is for the whole window. High specification glass units with surface coatings, together with air or inert gas filled double or triple glazing, will produce lower U-values.

Energy Rating

This measures the window's solar gain and air leakage. Ratings are classified in bands from A to G where A is the best.

Cavity closers

Using an insulated cavity closer system to create accurate window apertures will give an engineered fit for the window. Make sure the measurements of brickwork apertures is accurate and the correct size sill is specified. Use ties that fix to the window jamb and then screw into the brickwork for ease of installation.


The Code for Sustainable Homes promotes security. You can add more weight to your project proposal by noting the security performance of your chosen window. Jewson supplies windows that comply with the requirements of the Police preferred specification, 'Secured by Design'.

Why choose timber windows?

Today, many people prefer real wood windows for both their visual appeal and flexibility of design. Things to consider when deciding which window best suits your project include:

  • Architectural style - timber windows allow greater flexibility of design.
  • A range of fully finished colour options offering low maintenance.
  • Easily maintained or repaired, without the need for long term replacement.


Trade Tips

  • Jewson supplies FSC windows through a national network of branches.
  • The use of cavity closers provides a better fit.
  • A factory pre-painted finish lasts longer and avoids work on-site.

Homeowner Benefits

  • Hardwood windows give greater durability.
  • Wood improves the aesthetic look of the building.

Jewson has everything you'll need...

  • Special order; Your local Jewson branch has a full range of windows to choose from and can provide you with all the technical information you need. We offer a full bespoke and special order service and a wide range of window fixings and window sill boards.
  • Catalogue and displays; Our branches have thousands of windows to choose from including: timber, UPVC, sash and 'Secured by Design'. See our displays or pick up a catalogue.