What is the Cheapest fabric/material ........? What is the Cheapest fabric/material that would work best for blocking the...

What is the Cheapest fabric/material that would work best for blocking the Sun and heat surrounded by theSummer. I just want textile so I can add it on the curtains I already enjoy or be able to engender my own.
Is this ornate conception childish?
Answers:    Mama Kim is absolutely right!

Check beside your local linen outlet, they often hold odd size sheets on Dutch auction for just a $1.50! We bejewelled my daughters room with them, adjectives sorts of colors, *******, turquoise, yellow, different color for every pane.
Name for my house?
There is a backing you can add on to your curtains ... We've always call it blackout (it kind of reminds me of those antiquated shades that would roll up ... you know?). You can find any fabric - heavier - & sew it to the put a bet on of it when you make the curtains. I wouldn't walk too light on the material as you may have trouble totalling the blackout.