Cleaner greener windows keep out the cold
As gales howl through chinks in our property’s armour, we reveal how the latest window advances are helping to keep out the cold. Sharon Dale reports.
SUM up the sixties and you might say: free love, fabulous fashion and fantastic music.
You could also add freezing cold. When you heaved off your five blankets on a winter’s morning there was ice on the inside of the windows and wind whistled through the surrounding frame. Later on condensation would drip into lakes on the sill.
Manufacturers and scientists have worked hard over the past 50 years to find a solution to these problems, and modern frames and glazing can be incredibly energyefficient. Pilkington has been at the forefront of new glazing technology. It introduced its K Glass in the late 1970s. The argonfilled double glazing helps prevent heat escaping from the home and an invisible metal coating on the glass reflects heat back into the room, harnessing the sun’s natural warmth. Its energiKare glass, which is 75 per cent more efficient than single glazing, comes with an outer pane of Optiwhite, an extra clear glass and architects regularly specify Pilikington’s self-cleaning panes for hard-to-reach roof lights.
Garry Smith, Technical Advisory Service Manager at Pilkington, says: “It was recognised very early on in the 1800s that putting two panes of glass together was better than having a single pane, but the problem then was the sealants. That issue wasn’t resolved until the 1960s.
“That’s when double glazing became common and we managed to halve the U value, which is the amount of heat lost from windows. Then people realised that if you made the gap between the two panes bigger it improved the thermal performance. Coatings and K Glass came in the late 70s and they were exciting. A thin metal coating is applied to the glass inside the sealed unit and it works a bit like a silver teapot in that it conducts heat. That brought U values for double glazing down from 5.4 to 1.7.” The next challenge was to get the U value of glass down to around the same as brick and block work, which is below one. This was achieved by filling the space between the two panes with argon, a poor convector of heat, which stops warmth leaving through the window and brought the U value to 1.5. It all meant a massive improvement in thermal performance, which is good.
“I can remember the old single glazed windows in my parents’ cottage. They were dripping with condensation and you could feel the draught as you walked past,” says Garry. Pilkington’s most recent products include a Japanese innovation known as Spacia or Legacy. This ultra thin double glazing that looks like a single pane of glass and is useful for period properties and some listed buildings.
Triple glazing, which is common in Germany and Scandinavia and has a U value of 0.6, is also becoming more popular here.
“We make the glass here at Pilkington and export it to Northern Europe, where they frame it. People here buy the units there and have the glass shipped back over. The problem with finding it here was with the framers, but they’re catching up now they realise there is a market,” says Garry.
There is also a burgeoning market for wooden frames.
Malcolm Ambler, of Timber Windows at Harewood, near Leeds, says: “PVC frames were introduced in the 70s and they came at a time when timber ones were poor quality. The wood wasn’t seasoned or preserved, which meant they warped and rotted easily. They also didn’t take double glazing easily. That made PVC very popular.”
Now many owners of period properties are ripping their plastic windows out and returning to wood. “Things have come full circle. Years ago it was a selling point to have PVC windows but the problem is that they don’t look right in older properties and can actually devalue the house.”
Advances mean that timber is now a practical, low maintenance alternative.“Our windows are made from treated European redwood wood and from engineered timber, which is a bit like plywood, in that strips of timber that are bonded together and machined. This makes them much stronger and prevents warping,” says Malcolm.
They are then factory finished with micro porous paint, which allows the timber to breathe and is guaranteed to last eight years.
They do cost between three and four times more than PVC frames, but says Malcolm: “They look nicer and they make a property more desirable as well as adding value, so you could say they are a good investment.”
TIME TRAVEL: This house was designed in the 1970s but has been brought into the 21st century by Simi and John Standeven.
GOOD WOOD: Timber frames, like these from Timber windows at Harewood, are becoming very popular.