The Natural Philosopher wrote:

Frank Lee Speke-King wrote:

One cold night last winter, 0degC outside, I placed our weather
station's outside thermometer betweem the window and the net curtain,
and sat back to watch.

Eventually, the inside thermometer was reading 22degC, but the one
behind the curtains wasn't far off 0degC, about 2 IIRC.

Those curtains were - and are - doing a fine job.

Was that SG? if so and you had say -2 outside, that would put the
curtains at about 4:1 better than the SG..say around 1 or 1.2 U value.

About twice as good as DG.

Aluminium patio door and window frame, about 8'w x 6'h, 1" air gap
between the DG panels.

--

Frank