Rice husk, the main by-product of milling paddy, is one of the more easily available and abundant renewable energy resources. None of the husk combustion systems available at present is suitable for those who have relatively modest energy requirements and whose options in the matter of alternate energy sources are limited and costly. Decentralised post-harvest processing and small scale rural industries are examples. The Tube-in-Basket (TiB) husk burner described here is a compact, simple and easy-to-fabricate device, which produces a clean and concentrated flame with high combustion efficiency. As a low cost heat module, using an agro-residue as fuel, TiB holds promise of contributing towards meeting the energy demand of the rural segment of society in the underdeveloped countries. Part I of this communication deals with rice husk, its combustion characteristics, and some pertinent aspects of the existing husk combustion systems. It then describes the design criteria for TiB taking into account the properties of husk as a fuel. Performance data of a prototype batch TiB is included to demonstrate the validity of the basic design.