DIY Doctor UK DIY Forums

Hi,we're renovating our 50 year old house, we want to install highy ecological materials.What kind of windows should we chose to save energy? Are double glazed windows enough or should we pick triple glazed? Sliding sash? Tilt & turn? We've already chosen the manufacturer - http://klassen24.co.uk/, their products are made out of ecologically certified wood. Please help us chose the right type.

Ahhh. Sustainably sourced in reality means plantation grown pine, normally Monterey Pine, or Pinus Radiata. Here the sustainability means that it is chosen because it grows really quickly and that makes it commercially viable. It of course does nothing for it's longevity, it grows so fast that the growth rings are far apart, and of course it has little rot resistance. If you must go for softwood, I would suggest accoya, a pickling treatment done to the timber to replace hydroxyl groups with acetyl groups, making the timber less inclined to absorb water. Or choose hardwood windows, there is plenty of oak grown in Europe for commercial purposes that is sustainable, and will last much better. Durability and lifetime are a BIG part of your ownership cost, and of the ecological impact of your windows.
As for the glazing, and your overall energy efficiency, split your budget where it makes most difference, having hugely insulated windows and solid walls makes no sense at all, and if you are making your house airtight, you may want to consider a heat exchanger to ensure you get ventilation and heat recovery from the exhausted air. Double glazing with an expensive gas is normally as good as and cheaper than triple glazing, in my humble experience.