Remedies: windows

Original windows are unlikely to be double-glazed and may not be airtight. Original frames may be in poor condition.


Back to top


Original aluminium windows and doors, unless well maintained, may be in poor condition and may need maintenance or replacement. Possible problems and solutions include:

  • pitting of the exterior anodised aluminium - they may be able to be sanded and recoated (some businesses offer re-finishing of aluminium joinery).
  • sashes that will not open freely - the frame may have twisted or the friction stays are too tight. Friction stays that are too tight will require adjusting or replacing
  • sashes that will not stay open - worn-out stays must be replaced 
  • blocked condensation outlets - clear outlets and remove obstructions. 
  • deteriorating seals to frame joints - these will eventually result in water entry into the wall framing. If the windows have removable glazing beads, remove the beads and a temporary fix may be able to be achieved with sealant. Typically, where frame seals have failed the window will need to be removed and refurbished. Where seals and glazing rubbers need replacement it may be more cost-effective to replace the window rather than refurbish, as this also provides the benefit of the better performance of newer aluminium windows plus allows the windows to be double glazed. Work should be carried out by a specialist.
  • scratched interior or exterior surface - treat in the same way as for pitting
  • worn rollers to sliding doors - replace
  • worn hardware - replace.

Some aluminium windows had easily removable plastic (or later, aluminium) glazing beads which meant glass could be removed from the outside, reducing the security of the dwelling.

Where original windows that have fixing flanges behind the cladding are to be removed, it will be necessary to remove architraves and then either cut the flanges with a sabre saw or remove enough of the cladding to allow removal.

Back to top


If properly detailed, installed and maintained, timber window frames and sashes are likely to be in good condition. Hinges, particularly in corrosive environments, and worn stays may need replacement.

If there is minor deterioration to timber paintwork but not to the timber itself, sand the windows back and repaint. Ensure that top and bottom edges of sashes are sealed to prevent moisture ingress into the timber.

Window sashes that have rotted due to moisture getting into the timber, must be removed and repaired by inserting a new section of timber, or replaced with a new sash.

Sashes that are sticking because of paint-clogging, can usually be freed by running a knife or blade between the sash and the frame to cut the paint.

Back to top

Thermal efficiency

Windows will be single glazed units unless they have recently been replaced. Single glazing has a poor thermal performance and may contribute to condensation problems. Retrofitting insulating glass units (IGUs) is the best option to improve the thermal efficiency of windows but can be costly.

A single-glazed aluminium joinery unit can sometimes be replaced by a new double glazed sash unit. Another, cheaper, option may be to insert a removable second pane of glass or a plastic material (called secondary glazing) to the inside of the existing pane. This can be done by mechanical or magnetic attachment and can provide many of the benefits of IGUs.

The options to retrofit double glazed units into timber windows are dependent on the profile of the existing joinery. Options may include:

  • removal, refurbishment, upgrading and reinstallation of the widow unit
  • complete replacement of the window
  • replacement of glazing only
  • replacement of the sashes with a new sash that can accommodate an IGU (including the installation of aluminium sashes into existing timber frames)
  • installation of an adaptor system to allow joinery to accept IGUs.

Thermal efficiency of windows can be further improved by installing heavy drapes to reduce draughts and retain heat.

Back to top


Over time, original aluminium windows will leak more air than a new window as the seals deteriorate and the stays wear. Weather seals and stays on aluminium windows can usually be easily replaced.

Timber windows tend to be relatively air leaky and therefore inefficient in terms of maintaining and retaining heat within the building. Ensure that window sashes fit snugly into frames without wide gaps and install draught-stopping foam seals around gaps in the window frames.

Aluminium and timber windows were fitted into rough opening that was typically bigger than the outside dimensions of the window reveal/frame. The gap, which can be a significant source of air leakage into the building, was traditionally covered by the architraves. To reduce the air leakage, remove the architraves, insert a PEF backing rod then apply a bead of expanding foam before replacing the architraves.

With the advent of slimline reveals, the window had to be installed before the wall lining was fixed to allow the lining material to be fitted into the rebate. In these cases, new air seals cannot be added unless the wall is being relined.