cheap forms of mylar ?

I want to line my roof with mylar but i am having a hard time finding what i want. Any advice or leads would help. thanks!

I went through a bunch of different types before finally finding a good fit for the solar ovens we manufacture.
What are some of your parameters and maybe I would have a suggestion from the types I have looked at.

main thing is cost  I'm only need it for a solar shield its going to be covered with plaster

i would really like a 100'x100' sheet but i'm sure there is some law about covering your house with it

Just about everything I purchased was in 60 inch widths.
  One of the hydroponic products was very reflective on one side and white on the other about 6mil thick and I could join it with a heated seam sealer. So I guess you could make it larger if you wanted. I imagine it would be hard to manuver.
Stuff is so dang slippery though, what are you going over it with before you plaster? Expanded metal lath?

The shiny side of aluminized mylar typically needs to face an air space to function properly as a radiant barrier.  If that's what you want it to do.

HTH,

troy

mm ok alot to think about

They use mylar blankets at marathons. I read of someone gathering these up,washing and using them for a tiny house build. I understand that marathons now have recycling areas to drop off all the mylar blankets after using.

mm thats a good idea they are 2-3 each at the store

The marathons probably buy from someone like this:
http://www.shop.meyerscustomsupply.com/category.sc;jsessionid=64B501D2BEAAC8059645835D74274298.qscstrfrnt06?categoryId=42

They come 100 to the roll ($99), so you aren't paying for all of the individual wrapping.

I don't know what your budget is but the products at www.savenrg.com seem like cutting egde stuff.  The sheets were selling for $0.79 per square foot last time I checked, but they also have radiant barrier chips that are blown in like other loose fill insulation.  The advantage to this, in horizontal applications, is that the accuulation of dust, over time, will not degrade the performance of the chips.  The top layer will still get dust on them and stop performing as they orignally had, but the layers underneath the top layer will be protected from dust accumulation.  In using flat sheets in horizontal application (ceilings, under roof joists) the dust accumulation prevents the radiant energy from being reflected. 
They also have some sheet-type material that has multiple layers to stop the performance degradation caused by dust.