The rate of heat loss per square metre for a temperature difference of 1 degree Kelvin, or Celsius, between the interior and exterior.
How can I improve the U-value?
By using either a hard or softcoat low-e glass with Argon Gas in the cavity if necessary.
What standard are the units made to?
Can I have a cat flap in a double glazing unit?
Yes, buy a cat flap with a round hole for fitting into glass.
If I do not specify a spacer colour, what will I get?
Default spacer colours are silver for aluminium & black for warm edge.
Does the thickness of glass improve the insulation value?