Aspen Aerogels, Inc.

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On May 13, 2026, the Board of Directors of Aspen Aerogels, Inc. (the “Company”) designated Grant Thoele as the Company’s principal accounting officer, effective immediately, in addition to his current roles as the Company’s Chief Financial Officer, Treasurer and principal financial officer. Mr. Thoele assumed the responsibilities of principal accounting officer from Santhosh P. Daniel, who was serving as the Company’s Chief Accounting Officer and principal accounting officer. Mr. Thoele’s biographical information is included under the heading “Management and Corporate Governance - Information about our Executive Officers” in the Company’s Definitive Proxy Statement for its 2026 Annual Meeting of Stockholders filed with the Securities and Exchange Commission on March 27, 2026 and incorporated herein by reference. There is no arrangement or understanding between Mr. Thoele or any other person pursuant to which he was selected as an officer of the Company, and there are no family relationships between Mr. Thoele and any of the Company’s directors or executive officers. There are no transactions to which the Company is a party and in which Mr. Thoele has a direct or indirect material interest that would be required to be disclosed under Item 404(a) of Regulation S-K. On May 12, 2026, in recognition of Mr. Thoele’s contributions to the Company, the Compensation and Leadership Development Committee of the Company’s Board of Directors approved an increase in Mr. Thoele’s annual base salary to $425,000, effective as of April 1, 2026. Mr. Thoele’s target bonus opportunity for 2026 remains unchanged at 60% of his annual base salary.

Item 5.07. Submission of Matters to a Vote of Security Holders. On May 13, 2026, the Company held its Annual Meeting of Stockholders (the “Annual Meeting”) via live audio webcast on the Internet. Of the 82,825,603 shares of common stock issued and outstanding and eligible to vote as of the record date of March 16, 2026, a quorum of 70,437,282 shares, or 85.04% of the eligible shares, was present at the meeting or represented by proxy. The following actions were taken at the Annual Meeting: The following nominees were elected to serve on the Board of Directors as Class III directors until the 2029 annual meeting of stockholders and until their respective successors are duly elected and qualified, based on the following votes: Nominee Votes For Votes Withheld Broker Non-Votes ──────────────────────────────────────────────────────────────────────────────── Steven R. Mitchell 51,612,245 6,156,904 12,668,133 Donald R. Young 52,236,066 5,533,083 12,668,133 After the Annual Meeting, Cari Robinson and James E. Sweetnam continue to serve as Class I directors until the 2027 annual meeting of stockholders and Kathleen M. Kool and William P. Noglows continue to serve as Class II directors until the 2028 annual meeting of stockholders. The appointment of KPMG LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026 was ratified, based on the following votes: ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── For Against Abstain Broker Non-Votes ────────────────────────────────────────────────────────────── 69,845,522 571,148 20,612 - The Company’s stockholders approved, on a non-binding, advisory basis, the compensation of the Company’s named executive officers, as disclosed in the Company’s proxy statement for the Annual Meeting, based on the following votes: For Against Abstain Broker Non-Votes ──────────────────────────────────────────────────────────────── 49,538,581 7,344,203 886,365 12,668,133 The Company’s stockholders approved, on a non-binding, advisory basis, a one-year frequency of holding an advisory vote on the compensation of the named executive officers, based on the following votes: 1 Year 2 Years 3 Years Abstain Broker Non-Votes ───────────────────────────────────────────────────────────────────────────── 56,316,979 34,117 1,316,984 101,069 12,668,133 In light of the voting results concerning the frequency of future stockholder advisory votes on executive compensation that were delivered at the Company’s Annual Meeting, the Company’s Board of Directors has determined that the Company will hold an annual advisory vote on executive compensation until the next required vote on the frequency of stockholder votes on executive compensation. The Company is required to hold votes on frequency every six years. The Company’s stockholders approved, on a non-binding, advisory basis, a proposal regarding the future declassification of the Board of Directors, based on the following votes: For Against Abstain Broker Non-Votes ────────────────────────────────────────────────────────────── 57,012,251 665,791 91,107 12,668,133

Item 7.01. Regulation FD Disclosure. On May 14, 2026, the Company issued a press release providing an update on the initiation of the staged restart of its manufacturing facility in East Providence, Rhode Island. The press release is attached as Exhibit 99.1 hereto and incorporated herein by reference.