X0508 4 2023-08-08 0 0001145986 ASPEN AEROGELS INC ASPN 0001610257 Young Donald R C/O ASPEN AEROGELS, INC. 30 FORBES ROAD, BUILDING B NORTHBOROUGH MA 01532 1 1 0 0 President and CEO 0 Common Stock 2023-08-08 4 P 0 25000 6.8279 A 656703 D The price reported represents a weighted average price. These shares were purchased in multiple transactions at prices ranging from $6.745 to $7.00 per share. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price. Represents 149,603 shares of Common Stock, 45,484 RSUs and 461,616 shares of Restricted Stock. /s/ Virginia H. Johnson, Attorney-in-Fact 2023-08-08