A universal thermal mat costs about 67 euros, while a custom-made external screen for an integral motorhome can cost over 500 euros. However, the price does not indicate how much the heat will be reduced. In an ADAC test with seven identical cars, temperature reached 53 degrees without protection, 49 with an internal screen, 45 with an external screen, and 43 with a cover over the roof and all windows. External screens block sunlight before the glass and are generally more effective than internal ones, but proper fit and no gaps are crucial.
