Small windowsill means heat from radiator only rises behind closed curtains - what to do?

G_M

Radiator shelf

glennevis

How about anchoring the curtain with velcro? Install small piece of hook on each window frame in the bay and sew pieces of loop into the corresponding location on the curtains. If you use construction adhesive like 'sticks like sh*t' on the hooks they won't move. Just tap the curtains after closing them.