Windows are a lifeline to the outside world and hence should always be attractive and eye-appealing, as well as through. No drapery, colour or design can compensate for a dirty window. The function of windows is not as simple as creating a weatherproof view, they also:

  • Allow natural light in
  • Often allow ventilation
  • Have an aesthetic value
  • Allow the inhabitant to see outside the building without leaving it, (security)
  • Keep cold and sound transference to a minimum while catering for all of the above

The amount of natural light entering a room will be dependent on the windows, size and shape, how it is made, i.e. the number and size of mullions and transoms, its position in the room and the effects of internal and external reflection.

Ventilation – All habitable rooms must have a form of ventilation either mechanical (using ducts and fans) or natural, this is usually by opening windows. Opening windows for ventilation are the most common and economical forms of ventilation. Building regulations vary from country to country however a good rule of thumb to use is that the windows for the room must have an opening area of at least 10% of the floor area. This will need to be checked with your local building regulations. Kitchens, bathrooms, and laundries are different again because of odour, moisture and airborne bacteria. They are often required to have a form of mechanical ventilation in lieu of or as well as opening windows. One must check with the local authority and building regulators before you embark on a job that requires construction rather than decoration. Because of its very nature, a pane of glass is usually quite thin and transparent, especially in comparison to the wall in which it sits. The wall has been designed to stop or reduce the transference of heat, cold and noise and so should a window while still achieving all of its other functions. Unfortunately glass is a poor thermal insulator unless working in conjunction with an air gap. Various methods are used to stop or reduce the sound and thermal transference as much as practical. Double-glazing is the most common method of this.

            Ensuring that there is a good seal between the opening part of the window (the sash or casement) and the frame will reduce heat loss and improve sound insulation. Metal or plastic rubberised sealing strips around the rebates of the frame and opening sash will aid in achieving this. Glass companies are constantly improving glass technology and are experts in this field.


The frame for a window can be made from a number of materials, all of which are impervious and resilient to weather or coated to be so.

Steel – A steel extrusion shaped as a Z set in a timber surround. The glass is held in place either by wire clips with metal placement putty as the base and face putty over the top, or hollow steel glazing beads either screwed to the frame or clipped to studs in the frame.

Aluminium – Anodised or powder coated as a finish. The frame is set in the wall and the glazing is set into neoprene gaskets within the glazing beads, in the form of extrusion to match the frame, clipped and held in place by metal studs.

Timber – The frame is cut into its profile, sometimes with their sill attached or the sill being part of the cladding. The glass is held in place by laying it on the back of putty, holding it in place with glazing sprigs and finishing with face putty.

Double Windows / Double Glazing – A double window is two separate window sashes fixed to the same window frame. Double-Glazing consists of two sheets of glass fixed together with an air gap between, within the same rebate of the window frame. Both help reduce heat loss and increase sound insulation, but double windows increase sound insulation to a greater extent due to be increased distance between the panes of glass. With double-glazing the two glass panes are fixed together and the edges sealed. This is known as being hermiatically sealed. It can be made to suit the size of the window in most situations. There are various glasses that have beneficial properties such as Hush glass, and solar control glasses that control these factors to a degree. A sealed gap between two sheets of glass forms a system of double-glazing. A space of 20 millimetres is enough to improve thermal insulation however a gap of 150 to 200 millimeters is needed to reduce sound. Typical double-glazing with 20mm gap does give some sound reduction.


Sash – A frame in which panes of glass are set in a window or sometimes a door. The sash is usually referred to in sliding windows. E.g. opening sash, fixed sash, etc.

Casement – A window that opens on hinges, rather than sliding

Mullion – The central vertical members that may frame a window

Transom -The central horizontal member of a window

Sill – The horizontal member at the base of a window that forces water to run off and away from the building.

Bottom Rail – The bottom horizontal member of a casement or sash

Top Rail – The top horizontal member of a casement or sash

Vent Light – An opening part at the top or bottom of a window, hinged at either its top or bottom rail. If hinged at the top it opens out and if hinged at the bottom it usually opens in.

Fixed light – The glazed part of the window that is not hinged or opening. I.e. it is fixed in position


A basic window consists of a head, two jambs and a sill. If the window is divided horizontally, a transom would be used, if vertically a mullion. The area of glass is known as the light. The opening part of the light is called the casement if hinged and the sash if sliding.

Type a) Side hung casement

Type b) Top hung casement

Type c) Pivot hung casement

Type d) horizontal sliding sash

Type e) vertical sliding sash

Type f) louvered window

Type g) Round windows (often pivoted as they are difficult to hinge securely)

Type h) Dormer window, (usually casement)

Type i) Arched window

Type j) Bay window

Type k) Bow window


The curtains or other window coverings are obviously part of décor, but so is the view from the window. If the view is unattractive, it can be obstructed by net curtains, blinds or dark glass, which will allow light to enter but obstructs the view. If there is a blank wall in front of the window, it can be painted white to reflect light into the room or can be painted with attractive mural. Plants or flowers can also be hung on blank wall. An attractive view from the window can be framed by curtains.

BLINDS – They are used where it is difficult to hang curtains or to hide the view. They reduce heat loss in winter and keep rooms cool in summer, while still allowing in diffused light.

Roller blinds – These are available in a variety of fabrics and materials to go with the décor. These have been popular since the 18th Century. A roller blind is basically a stiff fabric wound onto a (usually) wooden roller, which incorporates a spring mechanism so that the blind can be raised or lowered to any position then released to recoil to its top rolled up state. It has a firm lath at the bottom to keep it straight, and the base is often decorated with frills, braid, fringing and accessories. They can be made of waterproof substances for bathrooms and kitchens and most are sponge cleanable, typically made of fabric or vinyl. They provide a very neat and tidy look and can be used on their own or have curtains over them. They can be made to measure. They are one of the most unobtrusive forms of window treatments as they take up a minimal space and cover only what is necessary when they are down. Conventional blinds roll from the back exposing the roller at the front, reverse-roll blinds roll from the front with the roller behind, and just to be different, and bottom up blinds can be fixed to the windowsill and pulled upwards.

Austrian Blinds – They are like Roman, as they move up and down with cords and rings, but they have a gathered heading and use vertical shirring which transforms the folds into soft scallops.

Pinoleum – These are slatted blinds made from wood or quill woven together with cotton. They give an oriental effect and are suitable for garden rooms or when a room needs to be screened from view.

Venetian blinds – They are horizontal blinds which have 2 inch wide slats held together with 1 inch wide cotton tape. These are made form slats of metal, wood or plastic slotted on cords which operate their opening or closing. Another set of cords raises or lowers the blinds. The amount of light entering the room can be adjusted by the slant of the slats. They tend to collect dirt and dust and are difficult to clean. They were the original horizontal blind and are heavy and difficult to clean.

Vertical louver blinds – These are like Venetian blinds hung vertically. By altering the angle of slats amount of light entering a room can be controlled. Slats can be of wood, stiffened silk canvas or any other man-made material. The slats are about 10cms wide, so care should be taken that if curtains are hung, they should be far enough from the blind to allow them to open.

Roman Blind / Shade – Are usually made of curtain fabric, but they can also be made from sheer fabric. They draw up from the bottom in a series of soft folds to look like a pelmet effect. This is done by cords threaded through rings at the back with dowels threaded through horizontally. They are flat when they are down. They are usually lined as they sit better. They use less fabric than curtains, but are more detailed to make. They can be installed inside the window frame or above the window frame to cover the joinery. They have a classic, elegant sophisticated look and suit living and dining rooms, and interiors that have simple lines and are not fussy. Be careful when selecting large patterned fabrics, as when folded up they can give a distorted look. A variation of this blind is the soft fold or hobbled roman blind. This is when the blind stays in soft folds when it is fully extended