Vacuum Infusion is a closed mould manufacturing process that can replace open mould processes. To improve resin flow it is common to add flow enhancement layers to the reinforcement stack. The basic feature for all flow enhancements is a coarse microstructure with regions of low fibre content. Degradation of mechanical properties due to environmental loading such as temperature and moisture is very important. A lot of research has been done on this area but earlier work has been done on materials without internal flow layer. The question is how well vacuum infused laminates, based on reinforcements containing internal flow layer, resist environmental ageing. Present work presents 3000 h 90 degrees C water ageing data and differences between the material types in the rate of water uptake, T-g, mechanical properties and density was investigated. The results show that the relative weight gain is an increasing function of time. From the T-g measurements we see that T-g is increasing for the immersion aged materials. Tensile tests after 3000 h of immersion ageing show a decrease in Young's modulus, tensile strength and failure strain for the immersion aged material. Density measurements show that the average density has increased for the immersion aged materials