February 13, 2023

       KNOW ALL BY THESE PRESENTS, that the undersigned hereby makes,
constitutes and appoints Elliot Kahler, as the undersigned's true and lawful
attorney-in-fact, with full power and authority as hereinafter described on
behalf of and in the name, place and stead of the undersigned to:

       (i)   execute for and on behalf of the undersigned, in the undersigned's
             capacity as a director, officer or beneficial owner of shares of
             common stock of Janus International Group, Inc., a Delaware
             corporation (the "Company"), any Schedule 13D or Schedule 13G, and
             any amendments, supplements or exhibits thereto (including any
             joint filing agreements) required to be filed by the undersigned
             under Section 13 of the Securities Exchange Act of 1934, as amended
             (the "Exchange Act"), and the rules and regulations promulgated
             thereunder, and any Forms 3, 4 and 5 and any amendments,
             supplements or exhibits thereto required to be filed by the
             undersigned under Section 16(a) of the Exchange Act;

       (ii)  do and perform any and all acts for and on behalf of the
             undersigned which may be necessary or desirable to complete and
             execute any such Schedule 13D, Schedule 13G, Form 3, 4, or 5 and
             timely file such forms with the United States Securities and
             Exchange Commission and any stock exchange on which the common
             stock of the Company is then listed; and

       (iii) take any other action of any type whatsoever in connection with
             the foregoing which, in the opinion of such attorney-in-fact, may
             be of benefit to, in the best interest of, or legally required by,
             the undersigned, it being understood that the documents executed
             by such attorney-in-fact on behalf of the undersigned pursuant to
             this Power of Attorney shall be in such form and shall contain such
             terms and conditions as such attorney-in-fact may approve in such
             attorney-in- fact's discretion.

       The undersigned hereby grants to such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact's substitute or
substitutes, shall lawfully do or cause to be done by virtue of this Power of
Attorney and the rights and powers herein granted. The undersigned acknowledges
that the foregoing attorney-in-fact, in serving in such capacity at the request
of the undersigned, is not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 13 and Section 16 of the
Exchange Act.

       This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file reports or schedules under Section 13
or Section 16 of the Exchange Act with respect to the undersigned's holdings of
and transactions in securities issued by the Company, unless earlier revoked by
the undersigned in a signed writing delivered to the foregoing attorney-in-fact.

                              [signature page to follow]

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of the date first written above.

                                       By: /s/ David Vanevenhoven
                                       Name: David Vanevenhoven
                                       Title: Chief Accounting Officer