To develop a polymer-based aerogel composite with high fire safety and strength for efficient building insulation, the hydrophobic phenolic/silica aerogel composites (PSACs) were synthesized using a facile self-catalyzed sol-gel process based on co-condensation of resorcinol (R), formaldehyde (F), and 3- (aminopropyl) triethoxysilane (A). The hydrophobicity was achieved by gas-phase modification of aerogels. Hydrophobicity and thermal conductivity of PSACs are governed by the R/A ratio and aerogel density, respectively. A glass fiber paper reinforced PSAC with a R/A ratio of 2 and an aerogel density around 0.10 g/cm3 (GP/RA21-10) exhibits high water contact angle of 138°, low thermal conductivity of 0.021 W m-1 K-1, and high strength (1.67 MPa of compression strength, 2.54 MPa of tensile strength, and 1.65 MPa of flexural strength). GP/RA21-10 exhibits significantly superior thermal insulation properties compared to commercial insulation materials including thermosetting polystyrene board, silica aerogel coating board, and rock wool. GP/RA21-10 is flame-retardant and high-temperature resistant, demonstrating superior fire safety for building insulation. This design offers substantial guidance for the advancement of high-performance insulation materials for buildings.