This paper aims to determine the feasibility of phosphoric acid-based geopolymer highly porous foams elaborated by a surfactant induced mechanical foaming. The processing and consolidation parameters of the basalt fibers reinforced foams were determined. The influence of the aluminosilicate source on the synthesis of usable samples is reported, showing that the Si/Al ratio as well as the reactivity of the source is crucial to ensure a good consolidation. The effect of the Al/P composition of the geopolymer foam on its properties is also discussed. Two optimal formulations with very good properties (water and temperature resistance, mechanical strength, low thermal conductivity) could be established. Their working properties as well as their main physico-chemical characteristics, allowing to understand their formation mechanism were studied. Both withstood immersion in water and exposition to high temperatures. Their size may also be increased without any difference. Their insulating (61 to 75 mW.m-1 K-1) and mechanical performances (80 to 190 kPa) are reported, as well as the study of their networks and microstructures.