Common problems include poor thermal performance, jamming and sticking, and rot or warping.
Most bungalows will still have their original windows, though in some they have been replaced – for example with aluminium glazing units.
Timber frames are durable and strong but they must have regular maintenance. If they are not properly protected from moisture (by painting), they can rot, swell, warp and stick.
Original bungalow windows were single glazed, and may also be relatively air leaky – making them inefficient in terms of maintaining and retaining heat within the building.
Even if the original windows have been replaced (for example, with aluminium windows) it is likely that the replacement units will be single glazed and will not incorporate thermal breaks unless the replacement is very recent. These windows are, if anything, less efficient than the original timber frames in terms of thermal performance.
Improving thermal efficiency
Options for consideration to improve thermal efficiency (in approximate increasing cost order) are:
- installing heavy drapes that have a Velcro seal down each side of the window
- adding removable secondary glazing (see below) that can be installed to reduce heat loss in winter and removed in summer to maintain ventilation
- removing existing glass and replacing with insulated glazing units installed into the sash using a small aluminium section
- removing the existing sash and glass and modifying the sash to accept insulating glass units and reinstalling the sashes.
Secondary glazing is a less expensive option than insulating glass units. With this, plastic film, magnetically attached plastic sheet, plain or low-E glass is installed inside the existing glass with a still air gap between them.
Research (largely carried out at BRANZ) found that secondary glazing gave R-values from 0.36 to 0.57 m2 K/W. This confirms that secondary glazing can be used as a functional alternative to retrofitted insulating glass units (IGUs) in existing domestic single-glazed window frames. (In fact, the performance exceeded the expected performance of IGUs retrofitted into the existing framing due to the secondary glazing effectively insulating the framing.)
The cause of the window jamming must first be determined. It could be due to building settlement, rotten sashes, loose or corroded hinges and fittings, or a paint build-up.
If settlement is the cause of jamming, re-levelling the building may remedy the problem. Otherwise windows or doors will need to be removed and planed to provide sufficient clearance.
If the window sashes have rotted, it is likely that the sash will need to be removed and repaired with new sections or a matching sash made. Unless minor, rot in window frames usually means replacement.
If sashes are paint-clogged, they can generally be released by running a knife or blade between the sash and the frame to remove the paint and free the window.
It may be possible to fix problems by replacing damaged hinges or fittings.
Sometimes, original windows will have been replaced with aluminium units. While the style and proportion of the aluminium replacement windows may be appropriate to the bungalow style, sometimes there are unsuccessful retrofits. Consider replacing these as part of a renovation project.
Glass becomes brittle with age and matching original colours in broken leadlighting is also likely to be difficult. Options for repairing special glass include:
- replacing of all of the colour that might have a single piece broken (this may be expensive)
- remaking the window with new coloured glass (again, this may be expensive)
- finding an exact colour and size match at a demolition yard.
Another option is not to repair.