How to choose the right window and door frames - Debunking myths

When choosing what your door and window frames should be made of many householders think it’s a simple question of cost. Not so, says Mark Smith, Technical Manager at REHAU: “When choosing between the various materials on hand, a holistic view is essential to ensure you get the best value for your money over the long term. Multiple factors need to be taken into account.”

The four primary materials between which homeowners and their architects could choose – steel, timber, aluminium, and uPVC –stack up very differently, but the key is always to take all the factors into consideration.

HERE’S A GUIDE TO KEEP IN MIND:

Steel is the cheapest material, but it is susceptible to rust, and the putty used to fix the glazing in place cracks over time, letting water into the frame. Regular painting of the steel and replacement of the putty is necessary. Steel windows and doors don’t fit tightly, making it susceptible to water and wind. It is also an excellent conductor of heat, so it is thermally very inefficient, meaning a less comfortable building that is more expensive to heat or cool. Thermal inefficiency also means that the material does not suppress noise well. On the plus side, it can be painted any colour easily.

Timber has a similarly high burden of maintenance, requiring annual or biannual varnishing and repair, depending on the climate. The timber quality is also a factor in its longevity, with imported timber typically preferred. In the rainy season, timber tends to swell, but if you sand it, it is unlikely to fit snugly in winter when the wood contracts. Timber scores high on looks and is a very poor conductor of heat, so it is thermally very efficient and reduces noise.

Aluminium has an undeserved reputation for being maintenance free. Truthfully, its anodised coating, if properly specified for the prevailing climate, is resistant to rust but the way it is constructed makes it vulnerable to leaks. The problem is that the corners are joined by crimping, with silicon used to seal against water. When the silicon degrades, as it usually does, water can penetrate. The only solution is to renew the silicon inside the corner, no easy task. Like steel, aluminium is an excellent conductor of heat, so it is thermally inefficient – a hotter house in summer, colder in winter.

uPVC is constructed by fusing two members together, creating a water- and airtight corner that does not leak. In addition, its internal structure includes channels to take any moisture out of the frame.

While typical uPVC is white, REHAU has invested in a local paint plant to provide the market with a range of popular colours off the shelf: Charcoal, Anthracite grey, black and bronze. Coloured uPVC will require some colour maintenance, but this can be done by the homeowner very easily.

The internal construction is based on chambers, which provide a ‘hermal break’, which makes it thermally efficient – it also insulates the inside of the building from external noise. Smith says after replacing all his window frames with uPVC, the internal temperature of his house in winter went from 11-13°C to 16-17°C.

Of course, heat transfer is only one element in a house’s thermal efficiency –other factors include the material out of which the walls are constructed and roof insulation.

Previously, uPVC was priced significantly more than competitor products, but REHAU has developed a product specifically for the African market that comes in at the same price level as comparable aluminium products, Smith says.

“It's worth nothing that aluminium comes in various thicknesses, so when comparing costs one must compare apples with apples - only aluminium above 30.5mm can be compared with uPVC,” he notes. “Another critical point is that the long-term costs of maintenance must also form part of the decision process, along with the long- term costs for heating and cooling.”

REHAU client, John Long, says that he replaced his existing steel frames with uPVC because of the maintenance they required, and the lack of insulation against cold/ heat and wind. Since making the move, he has found huge benefit in the insulation, with a marked differential between the interior comfort level and the outside ambient temperature, with less energy required to control comfort levels. With double glazing installed, he estimates that outside noise has been reduced by around 80%.

Long says additional benefits include the convenience of the tilt and turning windows upstairs – as all windows can now easily be cleaned from the inside without the need for ladders. “And the multiple locks on the windows and doors for extra security as well as the film in the glass makes breaking through very difficult - a very good safety mechanism.”

“I was familiar with this material from living in Europe and rate it highly for its good looks, practicality and great security,” he enthuses. “The process of removing the old frames and substituting uPVC was overall, a great investment.”