In buildings, thermal insulation plays a vital role in improving energy efficiency, reducing operational costs, and supporting climate-responsive architectural design. However, traditional insulation materials often face limitations in performance, thickness constraints, and long-term durability posing challenges for high-performance and space-limited building applications. This chapter explores the integration of nanomaterial-based insulation as an innovative solution to these challenges, emphasizing its potential to revolutionize modern construction practices. It introduces a range of advanced nanomaterials, including aerogels, nanoclays, silica nanoparticles, and carbon-based structures, detailing their exceptional thermal, mechanical, and structural properties that enable superior insulation performance. The chapter also outlines key synthesis and fabrication methods that facilitate their incorporation into various building components. Central to the discussion are the mechanisms of heat transfer reduction in terms of conduction, convection, and radiation and how nanostructured materials effectively mitigate these pathways through tailored porosity, low-emissivity surfaces, and sealed microstructures. Practical applications are examined across walls, roofs, glazing systems, and interior elements, showcasing real-world implementation. The chapter concludes by summarizing the advancements, limitations, and future potential of nanomaterial-enhanced insulation in achieving energy-efficient, sustainable, and resilient building design.