1. Use enough insulation - most buildings are built with too little

Simply stated, the more insulation you incorporate into the structural elements of your home (such as the walls, roof and floor), the more heat it will retain and the more efficient it will be in use, don't forget to consider using insulation with good acoustic properties too. This is not an area to scrimp on or to cut corners it is one of the few things that is near impossible to put right cheaply later, without serious disruption, once your building is complete, when was the last time you heard someone complain they had "over insulated" their house?