As used in sections 8-37bb to 8-37dd, inclusive, “housing agency” means the Department of Housing, the Connecticut Housing Finance Authority and the Connecticut Housing Authority, and “income group” means one of the following household groups, adjusted for family size and based on the appropriate area median income established by the United States Department of Housing and Urban Development: (1) Households with incomes twenty-five per cent or less than the area median income; (2) households with incomes more than twenty-five per cent but not more than fifty per cent of the area median income; (3) households with incomes more than fifty per cent but not more than eighty per cent of the area median income; (4) households with incomes more than eighty per cent but not more than one hundred per cent of the area median income; and (5) households with incomes more than one hundred per cent of the area median income.