Double-Glazing, the Nuts & Bolts of Any Eco Flat

Before installing central heating or air conditioning, the most important part is insulating the flat 100%. This will reduce energy waste and save you heating and cooling costs in the long run, plus works very well against noise pollution. If a house has single-glazed windows, then these can be responsible for about one-fifth of the heat lost from the building. Double glazing should cut this loss in half. (via CAT)

First we exchanged the old and broken glass from our French windows for double-glazing. We went for double-glazing with a 12mm air gap (you probably get away with less in Spain) by the Spanish company Climalit for they produce locally and offer good quality. The price was also ok: for 18 windows (9m2) we paid €400. We also made sure the gaps between the doors and the doorframe were well sealed by putting a rubber self-adhesive foam strip which compresses and forms a tight seal when the door is closed. There’s not much point if you install double-glazing and loose your heat through other gaps. The draught-proof installation of our windows (3 doors with 6 windows each) was done by David del Blanco Rey and the company MOREL and came to roughly €1540.
All in all we can only recommend changing to double-glazing as we notice a big difference in temperature and especially noise (we live in the barrio Gótico, remember!). Plus the government is giving subventions of up to 50%. For more information, click here!* Our insulating cork floor is adding to the overall insulation of the flat.
If you are looking for a cheaper way to improve the performance of your windows, CAT recommend fitting ‘secondary glazing, which can be an additional window fitted on the inside of the existing frame, or a magnetic or adhesive pane to fit to the frame, or even just some clear plastic film stuck to the interior frame’ as an alternative to double-glazing. Here some facts:
'U-values' are a measure of thermal performance - the lower the value, the better a material or building element is as an insulator.
Specification : U-value
Single glazing : 5.5
Standard double glazing : 2.7
Double glazing, low-E coating : 1.8
Double glazing, low-E coating : 1.6 to 1.3
Triple glazing, multiple low-E coating and argon-filled : less than 1.0’
(via CAT)

Other ways to insulate your home are installing wall panels (lots of eco materials available like hemp, cork,...) for thin walls or just hanging thick curtains during the winter months. The old cosy sweater is obviously the most eco-friendly option as are sun blinds (preferably those who let the air circulate) against the heat in summer!

Related Links:
CAT- Center for Alternative Technology
Barcelona governmental aid for improving urban landscape
Climalit
TreeHugger green insulation
TreeHugger guide on how to green your heating
Why insulate?

* 4 months later, we received €194,24 (13%) towards the total of €1540 we spent on double glazing and installation. The government's way of calculating the subventions is quite artful and disappointing for us. And beware of the paperwork!