Sistema de aproveitamento de águas pluviais (SAAP): análise da viabilidade técnico-econômica e influência no IPTU-Verde em um empreendimento da faixa 3 do Programa de Habitação Popular da Caixa Econômica Federal no município de Limeira/SP

Abstract

Rainwater harvesting is an appealing strategy in the context of the water crisis and growing public awareness. Consequently, techniques and methods are being developed to enhance the efficiency of rainwater harvesting systems (SAAP). While acquiring such a system requires a significant initial investment, the fact that a large portion of the Brazilian population is low-income makes rainwater harvesting financially unfeasible for many. Social housing programs (HIS) help these families achieve homeownership, and "Green Property Tax" (IPTU Verde) initiatives can provide them with tax benefits. The challenge lies in optimizing the relationship between the space occupied, implementation costs, and system operation for an SAAP within a "Tier 3" development under Caixa Econômica Federal’s low-income housing program in the municipality of Limeira, São Paulo. This study aims to evaluate—using computational analysis via Netuno software—the feasibility of implementing a rainwater system in a project under the Federal Government's *Minha Casa, Minha Vida* program. It also analyzes the cost-benefit ratio, taking into account the tax relief provided by Bill No. 162/2020. Reservoir volumes were calculated for three scenarios; Scenario 3 proved to be the most viable in terms of construction and alignment with the developer's policies, factoring in rainwater usage for garden irrigation and the cleaning of common areas. The acquisition of the SAAP, combined with the other sustainability features already adopted by the construction company, resulted in a 50% discount on property taxes (IPTU)—with 10% attributed solely to the implementation of the SAAP, in accordance with the provisions of Bill No. 162/2020 ("Green IPTU"). Following system sizing calculations and an assessment of estimated implementation costs, the ratio between the tax benefit gained and the implementation cost was determined to be 84.95%, thereby rendering the operation both technically and economically viable.