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.

Yorkshire Post - Property - - PROPERTY -

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.

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