Certain improved scenarios can experience an increase in heating requirement in comparison to the existing. This is likely to be caused by reduced internal gains from incidental sources caused by inefficiencies in other areas which have now been improved. Examples of areas in which this may happen are as follows: Improved lighting: Where lighting has been improved there is likely to be reduced heat generated by the fitting. Where this would have previously conditioned the internal environment to some extent the heating system will now have to compensate. The improvement would be likely to have a net gain. Improved water heating system: Where the water heating system has been improved it is likely to result in reduced thermal losses to the internal environment. This may be due to improved lagging of storage. This will have to be compensated for by the heating system however, the net change is likely to be an improvement. In all instances the net change should be a reduced annual cost. Regards, The Lifespan SAP Team