My 2nd greenhouse, with hardwood windows, all double glazing!!
I have an L- shape 450 m2 garden in an allotment (community garden complex), with my 20 m2 greenhouse, built 2 yrs ago http://www.instructables.com/id/5-x-4-m-greenhouse/
on it, there was also a small old existing greenhouse.
This is a rebuild from scratch.
Costs: ca. E 300.-
Building time: several months on weekends and holidays, finishing always takes more time (garden tasks get priority in tyhe growing season!