This work aims to improve water productivity in solar stills by reducing heat loss through green composite insulators to ensure storage of the absorbed thermal energy. Two green composite materials were proposed and presented. The first is made of date palm fiber and mortar (PFM), and the second is made of date palm fiber and gypsum (PFG). Three identical solar distillers were designed and tested under the same meteorological conditions of El Oued, Algeria. The first is the reference case (RSW distiller) where a 5 cm thick wooden box is used as insulation. The second (MSD-PFM distiller) is insulated with a 2.5 cm thick PFM composite material and then installed inside a 2.5 cm thick wooden box. The third (MSD-PFG distiller) is insulated with a 2.5 cm thick PFG composite material and then installed inside a 2.5 cm thick wooden box. The thermal conductivity of the proposed composite insulators was first determined experimentally and then used as insulators. Results showed that the accumulated water production from the MSD-PFG (4100 mlm-2day-1) is higher than that of the MSD-PFM (3400 mlm-2day-1) and RSW solar distillers (2800 mlm-2day-1) by 21.5 % and 46.43 %, respectively. The improvement in thermal efficiency of the proposed MSD-PFG and MSD-PFM were 45.77 % and 21.14 %, respectively. The economic analysis showed that the improvement in the production cost by MSD-PFG (0.011 $/liter) and MSD-PFM (0.0153 $/liter) were 31.68 % and 4.97 %, respectively. The sustainability, eco-friendliness, and cost-effectiveness of composite date palm make it an attractive option for insulation applications in solar distillers.