Energy efficiency for the purpose of sustainability is being taken up increasingly at present. Increasing the energy efficiency of buildings is being taken more seriously; consequently the demand for energy efficient buildings has risen. Heat losses can be reduced by lowering the heat transfer coefficient (U-value) of the building fabric by applying insulation in the building envelope, and so vacuum insulation panels (VIPs) can play a vital role in reducing the heat loss in buildings. VIPs represent a high performance thermal insulation material solution, offering an alternative to thick wall sections and large amounts of traditional insulation in modern buildings. Recently several researchers have carried out work to improve the performance of VIPs for building applications. The purpose of this paper is to study the possibility of improving U-value of external walls to achieve level 6 of Code of Sustainable Homes CSH. External wall with 0.22 W/m2K U-value of one house in Nottingham have been chosen as a case study for this paper. The main goal of this experiment and Simulation are to determine the reduction of heating load of the retrofitted walls and calculate the payback period of the optimisation with VIPs and Conventional insulation.