Housing for the 21st Century ActThis bill revises federal housing programs, including by expanding available financing for affordable housing and providing grants for planning and community development activities.For example, the bill increases the statutory maximum loan limits for mortgage insurance programs administered by the Federal Housing Administration for multifamily homes and requires the use of a more specific inflation index for such loans.The bill also increases the maximum eligible income for the Department of Housing and Urban Development's (HUD's) HOME Investment Partnerships Program (grants to states and localities to support housing for low-income households) and establishes a grant program to assist regional, state, and local entities with strategies to support affordable housing.In addition, the bill exempts certain housing-related activities from the environmental review process, including certain construction, improvement, or rehabilitation of residential buildings;excludes veterans' disability benefits from being considered as income for purposes of determining eligibility for the Veterans Affairs Supportive Housing (VASH) program;establishes a pilot program to provide grants to public housing agencies (PHAs) and other owners of federally assisted housing to test the efficacy of temperature sensors to support compliance with temperature requirements;eliminates the requirement that manufactured homes must be constructed with a permanent chassis; andauthorizes HUD to conduct performance reviews of organizations that provide housing counseling services.The bill also expands oversight of HUD and PHAs, such as by requiring PHAs to post information about contracts on their websites. For more information about this bill, see CRS Report R48849.