I expect a number of us have seen the domes of the Eden project, they are
geodetic tubular domes with the in fill being inflated transparent plastic
pillows. The plastic is a transparent ETFE, similar to fluon non stick
stuff.

I don't know how available this is but it strikes me the see through panes
used by wind surfers for sails might suit my purpose which is to provide a
temporay transparent insulating roof for a small quadrangle in the middle
of my daughter's flat. Its only 2.4m by 2m but as there are glass patio
type windows on three sides, adjacent to living space, in winter it loses a
lot of heat.

So I'm just considering the possibility of making this 2 by 2.4 pillow,
anchoring it at each corner and inflating it in situ, It will still let
rain past but should create a greenhouse of relatively still air in the
quadrangle.

But where to buy suitably strong plastic, being on the coast there may be a
gull problem?

AJH