Improving Federal Building Security Act of 2024 This act requires Facility Security Committees to respond to security recommendations issued by the Federal Protective Service (FPS) regarding facility security. A Facility Security Committee is a committee that (1) consists of representatives of all federal tenants in a specific nonmilitary facility, the security organization for the facility, and the owning or leasing federal tenant; and (2) is responsible for addressing facility-specific security issues and approving the implementation of security measures and practices in the facility. Not later than 90 days after the FPS issues a security recommendation to a Facility Security Committee, that committee must respond to the Department of Homeland Security (1) indicating if the committee intends to adopt or reject the recommendation; (2) describing the financial implications of adopting or rejecting the recommendation, including if the benefits outweigh the costs; and (3) providing DHS with a justification, if it intends to reject the recommendation, for accepting the risk posed by that rejection. DHS must (1) develop a procedure to monitor the recommendations and responses and take reasonable action to ensure Facility Security Committee response; and (2) report to Congress 270 days after this act's enactment and annually thereafter regarding such recommendations, responses, justifications for rejected recommendations, and risk mitigation efforts. The provisions of this act only apply to General Services Administration (GSA) facilities under FPS protection and non-GSA facilities that pay fees to the FPS for protection. This act ceases to be effective five years after enactment.