Adding extra double glazing?

Secondary Double Glazing is possibly what you mean.

I have it in one room - sliding glass panels in lightweight aluminium frames. I would guess that the same can be had with plastic panes - not sure.

Several years ago much was made in the UK press of a scientist at Harwell who used clingfilm as a cheap double glazing alternative.

https://www.youtube.com/watch?v=_IYuEI6mLRw

http://www.thisismoney.co.uk/money/experts/article-2081663/Does-double-glazing-cling-film-windows-stop-heat-loss.html

Peccavi
January 2013