ASPEN AEROGELS INC

(a)Appointment of Chief Operating Officer

On November 4, 2025, the Company promoted Gregg Landes to Chief Operating Officer of the Company. Mr. Landes has been with us since September 2016 and, prior to his promotion to Chief Operating Officer, he had served as Senior Vice President, Operations and Strategic Development since October 2019. Mr. Landes had previously served in a variety of positions with us, including as our Vice President, Strategic Development and Operational Excellence from May 2018 to October 2019, Vice President, Innovation and Strategic Development from February 2018 to May 2018, Vice President, Operational Excellence from March 2017 to January 2018, and Vice President, Finance and Corporate Development from September 2016 to March 2017. Prior to joining us, Mr. Landes was a principal at the consulting firm, Tetra Tech, Inc., where he focused on Liquified Natural Gas and Environmental Bankruptcy trusts from July 2013 to August 2016. Prior to Tetra Tech, Mr. Landes was employed by Hess Corporation, a large integrated oil and gas company, where he served as Vice President, Business Development for Hess LNG from June 2007 to July 2013. Prior to Hess Corporation, Mr. Landes worked in a broad range of senior financial and business leadership roles for Cabot Corporation, a leading global specialty chemical company. Mr. Landes holds a BSBA in Finance from the University of Florida and an MBA from the F.W. Olin Graduate School of Business at Babson College.

There is no arrangement or understanding between Mr. Landes and any other person pursuant to which he was selected as Chief Operating Officer of the Company. There are no transactions in which the Company is a participant and in which Mr. Landes has a material interest that are required to be disclosed under Item 404(a) of Regulation S-K. Mr. Landes has no family relationship with any directors or executive officers of the Company.

(c)10b5-1 Trading Plans

During the fiscal quarter ended September 30, 2025, the following directors and executive officers adopted a “rule 10b5-1 trading arrangement” (as defined in Item 408 of Regulation S-K of the Exchange Act) (the “Rule 10b5-1 Sales Plan”).

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On August 11, 2025, Donald R. Young, President and Chief Executive Officer of the Company and a director of the Company, 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 100,000 shares of our common stock until December 31, 2025.

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On August 12, 2025, Steven R. Mitchell, adirector of the Company, 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 57,541 shares of our common stock until November 12, 2026.

Except as disclosed above, none of our directors or executive officers adopted, modifiedor terminatedany contract, instruction orwritten 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 such term is defined in Item 408(a) of Regulation S-K, during the fiscal quarter ended September 30, 2025.