Are you talking about a reflective shade inside the cockpit? The reflective window shades you put on the inside of the window are fine for your car with its glass windows but not the best plan for your airplane with plastic windows. The reflective shades can concentrate energy like a magnifying glass. I know one of the major manufacturers of long range business jets recommends against the use of reflective shades inside the windows. I have heard most of the others have similar advice to operators but I have not seen it first hand.
RV-8 with the Showplanes Fastback conversion
Emp completed except for glass work
Wings completed except for bottom skin and glass work