Improvements to concrete will have a large impact in the construction and building sector. As the attention is drawn towards energy-efficient and zero emission buildings, the thermal properties of concrete will be important. Attempts are being made to decrease the thermal conductivity of concrete composites while retaining as much as possible of the mechanical strength. In this study experimental investigations of aerogel-incorporated mortar (AIM) with up to 80 vol% aerogel are prepared utilizing a reduced ultra-high performance concrete (UHPC) recipe. It was found that at 50 vol% aerogel content, the AIM sample possessed a compressive strength of 20 MPa and a thermal conductivity of ≈0.55 W/(mK). This strength decreased by almost a factor of 4–5.8 MPa, while gaining only a 20% improvement in thermal conductivity when aerogel content increased to 70 vol%. No preferred gain in properties was observed as compared to a normal mortar system. This can be attributed to the imbalance of the particle–matrix ratio in the mortar system, causing a decrease in adhesion of the binder-aggregates. The AIM samples have been characterized by thermal conductivity and mechanical strength measurements, alongside scanning electron microscope (SEM) analyses.