This research aims to develop a low density concrete, characterized by high porosity and reduced thermal conductivity with slight to no compromise over strength, employing scrapped waste tires. Although, literature on the topic is available that addresses benefits and drawbacks of rubberized concrete, this experimental work was formulated to suggest an optimum dose of crumb rubber that imparts sufficient strength and workability in addition to insulation and low weight. Four types of specimens were cost and tested, containing 0, 5, 10 and 15% crumb rubber as partial replacement of sand in ordinary concrete, using ASTM standards. Specially constructed heat transfer measurement device was used to find out the thermal conductivity of the specimens. Scanning electron microscopy was carried out to examine the micro-structure of rubberized concrete. Results reveal that thermal conductivity and density lower by 30% and 15% respectively and porosity increases by 34% at 15% partial replacement of sand by rubber. Higher concentration of voids along the interface were observed at 15% replacement indicating poor bonding and a weaker ITZ, leading to reduced strength. Based on the results, 5% optimum dosage is recommended, which enhances porosity by 5%, compressive strength by 5.5%, and reduces slump by 16%, thermal conductivity by 16% and density by 2% respectively.