Kind
 Cost per sq.metre
 Light transmission

K ( U ) =
 Watts per sq. M. per degree difference

 Thickness


Hence running cost
 (assume £600 for glass + bubble plastic)

 Capital cost of glazing  for 24ft long, 17ft wide house, on a dwarf wall.

Hort. Glass
 £4 per 2x2 piece.Assume 33% discount for quantity ,then = £7.25 p.sq.M.
 Assume 95%

5.5 for glass
 maybe 4.2 for glass with bubble plastic lining

 5mm ?
 6.6kg
 £600
 £520

 £13
 82%
 3.2
 10mm
 1.7kg
 £450


 £19
 78%
 2.4
 16mm
 2.7kg
 £385


 £25
 68%
 1.6
 25mm
 3.4kg
 £228


Note: polycarb is guaranteed for 10 years, but will at some time after that need replacing due to crazing and yellowing from UV.
The S factor, is the time taken to recover the extra cost .(i.e. extra cost in glazing divided by annual savings).
If it is less than 10 years  ( it always is) then it is economically efficient.
Also note that the extra cost of the 25mm over the 16mm is recovered faster  the sharply improved K factor is responsible as compared to the smaller increase in cost.
Geoff Hands, 2001