Many consider adoption of an energy efficient design approach as vital, so as to achieve a more sustainable built environment. The Malaysian government’s growing concerns and seriousness to embrace energy efficiency agenda is evident with the introduction of energy efficiency regulatory for commercial buildings and initiatives such as the government funded energy audit programme. This agenda poses a new challenge for architects and the building community as a whole to play their parts. To effectively produce energy efficient designs, architects need to adopt a quantitative tool to review energy impact of designs options especially at early design stage. The early stage of design is a critical part of the design process. This is when the design takes its shape and what transpired then becomes the basis to establish allocation of project resources in terms of budget, as well as design aids and expertise. A comprehensive method of performing energy saving estimation is through computer simulation. However use and availability of such sophisticated tools in design practices is currently limited. Alternatively a quantitatively derived design tool could serve to predict energy saving thus help architects in making informed design decisions. There are few efforts to develop such tool particularly for the Malaysian climate. This paper presents a research effort to formulate a simple design tool to predict the impact of wall envelope design options on the potential of energy savings due to daylighting. The study used IES<VE> integrated computer simulation programme to perform parametric studies on a generic building form. The results were then correlated with key envelope design variables to establish correlation equation that was later used to formulate the design tool. The reliability of the tool was demonstrated through an exercise to predict energy saving for an envelope design. The saving predicted was compared to the value generated using IES<VE> programme.