This paper presents an experimental study to investigate some of the thermal and strength behaviors of a new mortar material which was prepared by adding some of the residues of agricultural Iraqi biomass materials such as wood sawdust, reed, corn cobs, and their blending. These biomass materials are available in plenty of amounts in Iraq / Karbala City. These materials are blended with sand and cement, which are raw materials for mortar preparation, in different percentages to produce new types of mortar. The major focal area of interest is to identify the likelihood of applying these products as external wall insulating material to minimize heat transfer from outside to a building. Thermal conductivity, water absorption and skeletal density, and compressive strength at 7 and 28 days of the new mortars was also determined in the work. Comparing the performances obtained it was found that the new mortar containing wood sawdust had the highest compressive strength values While the best improvement in heat insulation was recorded in the mortar containing corn cobs compared to the other types. The results presented here prove that this mortar can be recommended for building purposes, specifically for exterior wall cladding. It provides good thermal resistance and improves the fortification of building walls; it also affords an added benefit of being cheaper and therefore fashionable for construction related uses.