In recent years, the demand for high performance thermal insulations has increased. While foam and aerogels have been researched for high performance thermal insulation, novel material design is required for further improvement. A porous silica has been found to have the potential to form a new thermal insulation material. However, porous silica is a powder and is difficult to form the porous compact. Therefore, we propose a composite insulation of powdered porous silica (p-SiO2), carbon nanotubes (CNTs) and sodium carboxy methyl cellulose (CMC). The fine voids and bulky structure of p-SiO2 greatly suppress gas and solid heat transfer. The composite of CNT can improve the moldability and enhance the mechanical properties. The moldability of thermal insulating materials improved even with the addition of 1 wt% CNT. With the addition of 1 wt% CNT, the increase in thermal conductivity was less than 0.01 W⋅m-1⋅K-1.