###### Abstract  
One of the growing concerns in the construction industry is energy consumption and energy efficiency in residential buildings. Moreover, management of non-degradable solid glass wastes is becoming a critical issue worldwide. Accordingly, incorporation of recycled expanded glass aggregates (EGA) as a substitution for natural fine aggregate in cement composites would be a sustainable solution in terms of energy consumption in the buildings and waste management. This experimental research aims to investigate the effects of EGA on fresh and hardened properties and thermal insulating performance of cement mortar. To enhance the mechanical properties and water resistance of the EGA-mortar, nano titanium dioxide (nTiO\({}_{2}\)) was used as nanofillers. The results showed an increase in workability and water absorption of the EGA-mortar. In addition, a significant decrease in bulk density and compressive strength observed by incorporating EGA into the cement mortar. The EGA-mortar exhibited a low heat transfer rate and excellent thermal insulation property. Furthermore, inclusion of nTiO\({}_{2}\) increased compressive strength and water resistance of EGA-mortar, however, their heat transfer rate was increased. The results demonstrated that EGA-mortar can be integrated into the building envelop or non-load bearing elements such as wall partition as a thermal resistance to reduce the energy consumption in residential buildings. industrial waste; sustainable concrete; recycled expanded glass  
development and decreasing the energy consumption in buildings [4; 5; 6]. It has been reported that the incorporation of insolation materials in the building can reduce the indoor temperature fluctuation up to 4 \({}^{\circ}\)C that would save 10-30% of energy usage [1; 2]. Although many investigations have been carried out on utilizing waste glass in the form of glass powder [7; 8; 9; 10; 11] and glass bead [12; 13; 14; 15] in concrete products, it has not found its position in the construction industry yet. Expanded glass aggregates (EGA), is a new commercial product, which are manufactured from waste and post-consumer glass. The EGA possess a relatively smooth surface with numerous encapsulated pores can be used as an insulating material [16]. The porous structure and low thermal conductivity of EGA can effectively reduce the heat transfer rate. The utilization of EGA in cementitious materials brings two-fold advantages, first, reducing the landfill cost and environment and secondly can reduce the energy consumption in buildings [16]. Recently, some studies [17; 18; 19; 20; 21] have been conducted to investigate the effect of EGA on mechanical and thermal properties of concrete and cement mortar, however, the utilization of EGA as an insulating material is at the initial stage. The great advantage of EGA is the possibility of production in a variety of size. Such a variety of particle sizes allows the improvement of the homogeneity of mixture and consequently reduces the possibility of segregation of the mixture [22]. [PERSON] et al. [23] and [PERSON] et al. [24] developed a cement-based lightweight composite using five different size of EGA (range between 0.1 and 2.0 mm) and reported the density of 1280-1490 kg/m\({}^{3}\) and compressive strength of 23.3-30.2 MPa. [PERSON] et al. [21] prepared cement mortar with two types of fine expanded aggregates (expanded glass and expanded clay) to compare their compressive strength and durability properties. In the mixes, they replaced the fine aggregates with expanded glass and expanded clay by the weight of the sand (8.5, 16.7, 33.3, 66.7, and 100 wt%). The obtained results revealed that in the mixtures with 100% EGA, the density decreased about 37% and the compressive strength after 28 days of curing dropped about 60%. The results also confirmed that EGA could be applied in the cementitious composites without limitation related to the alkali-silica reaction. In the experiment conducted by [PERSON] et al.