The following diagram illustrates the most common factors taken into account in building energy models:

• Conduction through building fabric: walls, windows, loft, floor, thermal bridges. Calculated via material U-values or thermal conductivity.
• Ventilation and Infiltration
• A Simple JavaScript model for calculating heat demand

• Metabolic (body heat)
• Lighting
• Appliances
• Cooking
• Hot water, including solar hot water
• Heating system

• Utilisation factors of gains
• Thermal mass

• A simple dynamic building model

• A simple radiator model
• A simple heatpump model

Simple annual The simplest of all models, possible to get good insight into energy performance with the least amount of calculations, but not as accurate as more detailed models.

Simple monthly A very common simple model type, used in SAP, more accurate than the annual model and gives insight into seasonal factors throughout a year. Require's higher detail datasets.

Dynamic simulations The simple model's use averaged annual, monthly datasets and so give outputs that are averages for a year/month. Dynamic simulations can give far greater detail and can be useful for finding out what happens in extremes of climate: hour-by-hour on a sunny day in June rather than the average for June.