This method may be used where the total area of glazing is 50% or less of the total wall area. Its advantage over the schedule method is that it allows a building with different building elements to be assessed as a whole, with adjustments being made between elements. For example, a wall R-value may be reduced if the roof or floor R-value is increased to compensate or if window R-values are increased. In no situations may R-values for roofs or walls be reduced below the minimum R-values set down by E3/AS1.