:wave
I made new curtains and bought the liner for them.
I camp in desert where not only does the liner keep light in or out, it is also a tremendous insulator for winter or summer. In hot weather or bright sun they keep egg actually cool inside
You will NOT regret lining them. You can see them in this photo
I found the curtain fabric for $1.98 a yard, and the liner cost me $16/yard. Almost didn't buy, but did the math and that meant that I would add $4 to price of each curtain totalling $5 each. I figured that for $40 for all my curtains the cost wasn't prohibitive.
The stuff is really cool. One layer is the pretty white side that you see up against the window, another layer is a vapor barrier, another layer is space-blanket mylar, and the last layer is cotton batting. Makes a totally opaque, highly insulated curtain. Made one for roof vent too.
I can close them off in the brightest sun and it is totally dark and cool inside.
If you're thinking about it, do it. You'll be very pleased.