The increasing production of fly ash and waste glass causes serious environmental challenge because of their permanency and potential toxicity. The recycling of these wastes to valuable products is a sustainable way for waste utilization. In the present work, starch was used as a natural porosity enhancer additive in producing fly ash–waste glass foam glass (FAGF) for thermal insulation. Sintering opened the pores to retain their original skeletal network; as a result, sponge-like foams were obtained. The waste glass was ground and filtered on the sieve with a 105 µm hole. A composition of waste glass, flying ash, silicon carbide (SiC) and rice starch was mixed in the required weight ratios. First, the mixture was pelletized using a mold to have a specific shape, and then sintering was carried out at 900 °C. Six formulations with different starch contents (0-6 wt%) had been formulated and tested for density, water absorption, compressive strength and thermal conductivities. The simple weight gain test fully demonstrates that high starch content contributes to higher porosity and lower density, thermal conductivity at the cost of moderate mechanical strength and increased water absorption. The optimum mixture with 6% starch had the minimum thermal conductivity of 0.10875 W/m·K, and acceptable compressive strength (8.66 MPa). This research showed that starch-modified FAGF could be an environmentally-friendly and adjustable insulation material using industrial and agricultural waste as raw materials.