ASPEN AEROGELS INC

Rule 10b5-1 Trading Plans

During the fiscal quarter ended December 31, 2024, the following of our directors or executive officers adopted, modified orterminated any contract, instruction or written plan for the purchase or sale of our securities that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) or any “non-Rule 10b5-1 trading arrangement” as defined in Item 408(c) of Regulation S-K:

On November 12, 2024, Corby Whitaker, our Senior Vice President, Sales and Marketing, adopteda Rule 10b5-1 Sales Plan. The plan is intended to satisfy the affirmative defense of Rule 10b5-1(c) and provides for the sale of up to an aggregate of 198,272 shares of our common stock, plus the net number of shares of our common stock underlying certain restricted stock unit (“RSU”) awards, until November 30, 2025. The number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is indeterminable with respect to the RSU awards, as such number is subject to the number of shares that will be automatically sold to satisfy applicable tax withholding obligations upon vesting of the RSU awards, which will vary based on the market price of our common stock at the time of vesting.

On November 13, 2024, Keith Schilling, our Senior Vice President, Technology, adopted a Rule 10b5-1 Sales Plan. The plan is intended to satisfy the affirmative defense of Rule 10b5-1(c) and provides for the sale of up to an aggregate of 37,786 shares of our common stock, plus the net number of shares of our common stock underlying certain restricted stock unit (“RSU”) awards, until September 30, 2025. The number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is indeterminable with respect to the RSU awards, as such number is subject to the number of shares that will be automatically sold to satisfy applicable tax withholding obligations upon vesting of the RSU awards, which will vary based on the market price of our common stock at the time of vesting.

On November 15, 2024, Stephanie Pittman, our Chief Human Resources Officer, adopted a Rule 10b5-1 Sales Plan. The plan is intended to satisfy the affirmative defense of Rule 10b5-1(c) and provides for the sale of up to an aggregate of 48,502 shares of our common stock until November 11, 2025.

On November 15, 2024, Gregg Landes, our Senior Vice President, Operations and Strategic Development, adopted a Rule 10b5-1 Sales Plan. The plan is intended to satisfy the affirmative defense of Rule 10b5-1(c) and provides for the sale of up to an aggregate of 261,836 shares of our common stock, plus the net number of shares of our common stock underlying certain restricted stock unit (“RSU”) awards, until November 30, 2025. The number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is indeterminable with respect to the RSU awards, as such number is subject to the number of shares that will be automatically sold to satisfy applicable tax withholding obligations upon vesting of the RSU awards, which will vary based on the market price of our common stock at the time of vesting.

On November 26, 2024, Virginia H. Johnson, our Chief Legal Officer, General Counsel & Corporate Secretary, adopted a Rule 10b5-1 Sales Plan. The plan is intended to satisfy the affirmative defense of Rule 10b5-1(c) and provides for the sale of up to an aggregate of 92,330 shares of our common stock, plus the net number of shares of our common stock underlying certain restricted stock unit (“RSU”) awards, until November 30, 2025. The number of shares to be sold pursuant to the Rule 10b5-1 trading arrangement is indeterminable with respect to the RSU awards, as such number is subject to the number of shares that will be automatically sold to satisfy applicable tax withholding obligations upon vesting of the RSU awards, which will vary based on the market price of our common stock at the time of vesting.