Insulation Basics – Double Glazing

Large single glazed windows are one of the biggest reasons for heat loss in a modern house.

It is also a major source of heat coming into the house in summer.

So what can you do?……………here is a comparison between single and double glazing.

Single Glazing
A single glazed window with an aluminium frame has a U value of around 7watts/degree C/m2 (an R value of 0.14 )

So if your house has got 30m2 of windows and its 5 degrees C outside.

You will be losing the following amount of heat through the windows if you keep the house at 20 degree C

30 x (20-5) x 7 = 3,150watts = 3.15kW/hour

For refrigerated cooling from 300C to 200C you will need the following amount of cooling to balance heat gain through windows:

30 x (30-20) x 7 = 2,100watts = 2.1kW/hour

Double Glazing

If you have double glazing with timber or uPVC frames you will reduce the U value to around 3 watts/degree C/m2 (An R value of 0.33 ).

For the same conditions as the above example the heat loss through the windows will be reduced to:

30 x (20-5) x 3 = 1350watts = 1.35kW/hour

For refrigerated cooling from 300C to 200C your heat gain through windows will be reduced to:

30 x (30-20) x 3 = 900watts = 0.9kW/hour

Other ways to reduce heat loss are

  • Reduce window size. As walls are better insulation than windows this can offer significant reductions in heat loss
  • Curtains or Blinds. Will provide similar performance to double glazing. . . but only during the time when they are closed.

Extra Benefits of Double Gazing

Improved Security: Its much more difficult, and noisy, to break in through a double glazed window.

External Noise Reduction The bigger the gap between glass the better the performance.

See Insulation for similar Posts

For Posts about Green Building see Sustainability

 

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