X0407 4 2023-06-01 0 0001145986 ASPEN AEROGELS INC ASPN 0001610279 Mitchell Steven R C/O ASPEN AEROGELS, INC. 30 FORBES ROAD, BUILDING B NORTHBOROUGH MA 01532 1 0 0 0 0 Common Stock 2023-06-01 4 A 0 7488 0.00 A 76719 D Stock Option (Right-to-Buy) 6.81 2023-06-01 4 A 0 7712 0.00 A 2033-06-01 Common Stock 7712 7712 D The reporting person was granted restricted shares of common stock representing a portion of the annual grant of equity for service as a non-employee director pursuant to the Issuer's Non-Employee Director Compensation Policy. These restricted shares will vest on the earlier of (a) June 1, 2024, or (b) the day prior to the Issuer's annual meeting of stockholders to be held in 2024. The reporting person was granted options representing the remaining portion of the annual grant of equity for service as a non-employee director pursuant to the Issuer's Non-Employee Director Compensation Policy. The options will vest on the earlier of (a) June 1, 2024, or (b) the day prior to the Issuer's annual meeting of stockholders to be held in 2024. Power of Attorney is attached hereto as Exhibit 24. /s/ Virginia H. Johnson, Attorney-in-Fact 2023-06-02