Common problems include poor thermal performance, jamming and sticking, and deterioration or corrosion of the frame.
Most art deco houses will still have their original windows, though in some they have been replaced – for example with aluminium glazing units.
Windows in art deco houses may be in poor condition due to the lack of protection from weather resulting from:
- the absence of eaves
- the fact that the hoods seen above windows – if they are present at all – provide only minimal protection from water coming down the wall
- the fact that flashings were minimal by current requirements and are likely to have corroded or moved in ways that open up gaps for moisture.
If timber window frames have not been properly protected from moisture, they may swell, warp, stick and rot. Steel frames may have corroded (Figure 1).
If window frames have deteriorated, they are likely to need replacement.
From a heritage point of view, timber is the preferred material for replacement of original timber frames, although this is likely to be considerably more expensive than other options. Timber frames can be double glazed or new sashes made if the rest of the frame is still sound. A well fitted timber window with double glazing is more thermally efficient than a double-glazed aluminium frame. Triple-glazing gives even better thermal performance, although its higher cost means that it is most likely to be considered only in very cold climates, or where noise is an issue. Triple glazing provides good sound insulation as well as thermal insulation.
Original window frames will be single glazed. Original timber frames may have been replaced by aluminium frames, which are likely to be more airtight than timber frames, but – unless installed very recently – are unlikely to incorporate thermal breaks or double glazing.Thermal efficiency can be improved by replacing original glazing units with new ones that incorporate double glazing and – if made from aluminium – thermal breaks. As noted above, for both heritage and thermal performance reasons timber is preferred, though it is more expensive. In cold areas of the country, use of argon gas in double glazing, or use of triple glazing, could be considered.
Other options for improving thermal efficiency (in approximate increasing cost order) are:
- installing heavy drapes that have a Velcro seal down each side of the window (the seals should be hidden by the drapes regardless of whether the drapes are open or closed)
- 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 insulating glass units installed into the sash using a small aluminium section.
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 or a build-up of paint.
Options to remedy the problem:
- 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 they should be replaced.
- 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. Any timber surfaces exposed should be sanded, primed and painted straight away to protect against moisture getting in.