ASPEN AEROGELS INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant☒

Filed by a Party other than the Registrant☐

Check the appropriate box:

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

Northborough, Massachusetts

April 10, 2024

Dear Aspen Aerogels, Inc. Stockholder:

You are cordially invited to attend the 2024 annual meeting of stockholders of Aspen Aerogels, Inc. to be held at 9:30 a.m. Eastern Time on Thursday, May 30, 2024. This year’s annual meeting will be conducted solely via live audio webcast on the Internet.

You will be able to attend our annual meeting, vote and submit your questions during the annual meeting by visiting www.virtualshareholdermeeting.com/ASPN2024. You will not be able to attend the annual meeting in person.

Details regarding the meeting, the business to be conducted at the meeting, and information about Aspen Aerogels that you should consider when you vote your shares are described in the accompanying proxy statement.

At the 2024 annual meeting, two persons will be elected to our Board of Directors (the “Board of Directors” or the “Board”). In addition, we ask stockholders to ratify the appointment of KPMG LLP as our independent registered public accounting firm for our fiscal year ending December 31, 2024, and to approve, on a non-binding, advisory basis, the compensation of the named executive officers, as disclosed in the accompanying proxy statement for the 2024 annual meeting of stockholders. Our Board of Directors recommends the election of the two nominees to our Board of Directors and a vote in favor of proposals (2) and (3). Such other business will be transacted as may properly come before the annual meeting.

Under Securities and Exchange Commission rules that allow companies to furnish proxy materials to stockholders over the Internet, we have elected to deliver our proxy materials to the majority of our stockholders over the Internet. This delivery process allows us to provide stockholders with the information they need, while at the same time conserving natural resources and lowering the cost of delivery. On or about April 10, 2024, we will send to our stockholders a Notice of Internet Availability of Proxy Materials (the “Notice”) containing instructions on how to access our proxy statement for our 2024 annual meeting of stockholders and our 2023 annual report to stockholders. The Notice also provides instructions on how to vote online and includes instructions on how to receive a paper copy of the proxy materials by mail.

We hope you will be able to attend the annual meeting. Whether you plan to attend the annual meeting or not, it is important that you cast your vote. Prior to the annual meeting, you may vote by proxy over the Internet as well as by telephone or by mail. When you have finished reading the proxy statement, you are urged to vote in accordance with the instructions set forth in the proxy statement. We encourage you to vote by proxy so that your shares will be represented and voted at the meeting, whether or not you can attend. Any stockholder attending the virtual annual meeting may vote online during the annual meeting, even if you already returned a proxy card or voted by proxy over the telephone or the Internet.

Thank you for your continued support of Aspen Aerogels, Inc. We look forward to seeing you at the annual meeting.

Sincerely,

Donald R. Young

President and Chief Executive Officer

NOTICE OF 2024 ANNUAL MEETING OF STOCKHOLDERS

TIME: 9:30 a.m. Eastern Time

DATE: Thursday, May 30, 2024

ACCESS: www.virtualshareholdermeeting.com/ASPN2024

This year’s annual meeting will be a virtual meeting via live webcast on the Internet. You will be able to attend the annual meeting, vote and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/ASPN2024 and providing relevant information, including the control number included in the Notice of Internet Availability or the proxy card or voting instruction form that you receive. For further information, please see the Important Information About the Annual Meeting and Voting beginning on page 4 of this proxy statement.

PURPOSES:

WHO MAY VOTE:

You may vote if you were the record owner of Aspen Aerogels, Inc.’s common stock at the close of business on April 3, 2024 (the “Record Date”). A list of registered stockholders as of the close of business on the Record Date will be available at our corporate headquarters for examination by any stockholder for any purpose germane to the annual meeting for a period of 10 days ending on the day before the date of the annual meeting. If you wish to view this list, please contact our Corporate Secretary at Aspen Aerogels, Inc., 30 Forbes Road, Building B, Northborough, Massachusetts 01532.

All stockholders are cordially invited to attend the virtual annual meeting. Whether you plan to attend the annual meeting or not, we urge you to vote by following the instructions in the Notice of Internet Availability of Proxy Materials or proxy materials you received and submit your proxy by the Internet, telephone or mail in order to ensure the presence of a quorum. You may change or revoke your proxy at any time before it is voted at the meeting.

By Order of the Board of Directors

Virginia H. Johnson

Chief Legal Officer, General Counsel,

Corporate Secretary & Chief Compliance Officer

Northborough, Massachusetts

April 10, 2024

CREATING VALUE THROUGH TECHNOLOGY, INNOVATION, AND EXECUTION

Dear Stakeholders,

In 2023, we set the stage for significant value creation in our Thermal Barrier and Energy Industrial businesses. Over the past year, teams across Aspen came together to scale business operations, drive innovation, eliminate the capacity constraints in our Energy Industrial business, and increase market adoption of our high-performance thermal barrier solutions. These successful initiatives played a pivotal role in our 2023 financial and operational progress. Our PyroThin® thermal barrier business achieved record annual revenues, reaching an impressive $110 million for the year, nearly doubling the segment’s revenue generation compared to 2022. In addition, we continued to diversify our customer base in this segment, signing contracts with three new major automotive OEMs. Equally impressive, our Energy Industrial business, which faced capacity constraints through the year, still demonstrated year-over-year growth, and exited 2023 with a meaningful backlog of orders to fulfill throughout 2024.

These results bode well for 2024 and beyond and are important indicators of the successful execution of our multi-year strategy to build a profitable growth engine that benefits all stakeholders: employees, customers, suppliers, communities, and investors alike.

2023 Highlights and Recent Business Developments

During the year 2023, the company focused on driving top line growth from both business segments, improving productivity and yields, maintaining careful control of operating expenses, optimizing the timing of capital expenditures, and accelerating on the path to near-term profitability.

Amidst the uncertainties of today’s global macroeconomic landscape, our focus on profitability remains top priority. To this point, we are steadfast in managing our fixed cost base, optimizing our current assets, executing against our quoted customer pipeline, and leveraging our supply partner to unlock additional capacity. We are well positioned to capture several industry tailwinds that have unfolded due to the global electrification movement and increasing demands for energy security.

Without our great team here at Aspen, none of this success would be possible. On behalf of the entire management team, I extend our deepest gratitude for your unwavering trust, confidence, and support. We remain committed to upholding the highest ethical standards in our relationships with all stakeholders, striving to exceed your expectations at every turn along the way.

Sincerely,

Donald R. Young

President & Chief Executive Officer

TABLE OF CONTENTS

PROXY STATEMENT FOR THE ASPEN AEROGELS, INC.

2024 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 30, 2024

This proxy statement, along with the accompanying notice of 2024 annual meeting of stockholders, contains information about the 2024 annual meeting of stockholders of Aspen Aerogels, Inc., including any adjournments or postponements of the annual meeting. We are holding the annual meeting at 9:30 a.m. Eastern Time on Thursday, May 30, 2024. This year’s annual meeting will be conducted solely via live audio webcast on the Internet. You will be able to attend our annual meeting, vote and submit your questions during the annual meeting by visiting www.virtualshareholdermeeting.com/ASPN2024. You will not be able to attend the annual meeting in person.

In this proxy statement, we refer to Aspen Aerogels, Inc. as “Aspen Aerogels,” “the Company,” “we,” “our” and “us.”

This proxy statement relates to the solicitation of proxies by our Board of Directors for use at the annual meeting.

On or about April 10, 2024, we intend to begin sending to our stockholders entitled to vote at the annual meeting the Notice of Internet Availability of Proxy Materials containing instructions on how to access our proxy statement for the 2024 annual meeting of stockholders and our 2023 annual report. Stockholders who have previously requested to receive paper copies of our proxy materials will receive paper copies of the proxy materials instead of a Notice of Internet Availability.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE

ANNUAL STOCKHOLDER MEETING TO BE HELD ON MAY 30, 2024

This proxy statement and our 2023 annual report to stockholders are available for viewing, printing and downloading at www.proxyvote.com. In order to view, print or download these materials, please have the 16-digit control number(s) that appears on your notice or proxy card available. On this website, you can also elect to receive future distributions of our proxy statements and annual reports to stockholders by electronic delivery.

Additionally, you can find a copy of our Annual Report on Form 10-K, which includes our financial statements, for the fiscal year ended December 31, 2023 on the website of the Securities and Exchange Commission, or the SEC, atwww.sec.gov, or in the “SEC Filings” tab of the “Financials” subsection of the “Investors” section of our website at www.aerogel.com. You may also obtain a printed copy of our Annual Report on Form 10-K, including our financial statements, from us, free of charge, by sending a written request to:

Attn: Investor Relations

Exhibits will be provided upon written request and payment of an appropriate processing fee.