Lightweight concrete has been studied because of superior combinations of low density, proper compressive strength and thermal insulation, improving the energy efficiency of constructions. This work aimed at evaluating the properties of lightweight mixes using combinations of expanded clay and expanded vermiculite. Six mixes containing CP II Z 32 Portland cement, two different expanded clays (maximum diameter 6.3 and 19 mm), two different expanded vermiculite (fineness modulus 3.42 and 3.20 mm), sand as coarse aggregate, superplastifier and water were produced. Fresh mixes were evaluated by slump tests, specific mass, water absorption and voids. The compressive strength and elastic modulus were measured using 10 cm x 20 cm samples. Thermal properties (conductivity, diffusivity and heat capacity) of samples with dimensions 5 cm x 10 cm were analyzed using a KD2 Pro thermal analyzer. The samples were cured in water, oven dried for 24 h and cooled down to room temperature during 24 h. Orifices were perforated in the concrete samples to insert a double-needled probe connected to the thermal analyzer. The specific mass of the samples ranged from 1500 to 1600 kg/m³. Therefore, the materials were classified as  lightweight concrete. The addition of vermiculite decreased the slump of concrete from 28.8 cm (standard sample, without vermiculite) to 10.2 cm (sample containing 3% fine vermiculite). Addition of 2 to 3% of vermiculite decreased the water absorption and voids and slighted increased the compressive strength of concrete at 28 days.  No significant change of the Young modulus was verified. The thermal conductivity and thermal diffusivity decreased with addition of vermiculite. The combinations of expanded clay and expanded vermiculite analyzed resulted in lightweight concrete with physical, mechanical and thermal properties adequate for improved thermal comfort in edifications located at low latitudes.