The heating audit looks at improvements to the heating system as a whole.
Heat Loss compared to Radiator and Boiler Output
The table below is a summary of the heat losses for all the elements of the house.
| Heat Loss | W/K |
| Walls | 69.39 |
| Floor | 39.72 |
| Roof | 10.44 |
| Windows | 77.87 |
| Ventilation | 27 |
| Total | 224.42 |
When the temperature outside is -1 deg C and inside 20 deg C then the heating required, from calculation, is 21 x 224.42 = 4.7kW.
The back boiler and radiators both provide a heat output of approximately 12kW and so the heating system should, in theory, be able to cope comfortably.
Energy Consumed by Boiler Pilot Light
| Pilot Heat Input | 210W = 0.210kW |
| Hours lit per year | 24 x 365 = 8760 |
| Units Consumed | 0.210 x 8760 = 1839.6 |
Energy Required to Heat Hot Water Cylinder
| Storage Capacity of Hot Water Cylinder | 80 litres = 80 kg |
| Cold Water Feed Temperature | 10 deg C |
| Hot Water Storage Temperature | 60 deg C |
| Specific Heat Capacity of Water | 4.2kJ/kg C |
Energy Required to Heat Water = 80 x 4.2 x 50 = 16800 kJ
Number of Units = 16800 / 3600 = 4.67 units
Energy Lost in Hot Water Feed Pipe
The kitchen is one of the major users of hot water. However, this is some distance from the hot water tank and a considerable amount of water has to be drawn off before hot water is obtained at the storage temperature.
| Pipe run length | 20m |
| Pipe inside diameter | 20mm |
Volume of water in pipe = 3.14 x (0.022 /4) x 20 = 0.00628 m3 = 6.28 Litres
If this volume of water is run off each time the tap is used to obtain really hot water.
Energy Lost in Hot Water Feed pipe = 6.28 x 4.2 x 50 = 1318.8 kJ
Number of Units = 1318.8 / 3600 = 0.37
If the tap is used 4 times a day, every day then the annual heat loss will be
4 x 365 x 0.37 = 540.2 kWh
Estimate gas used for hot water and cooking.
Gas is used to provide heating, hot water and cooking.
May, Jun, July gas consumption will be mainly hot water and cooking. The consumption for this period averaged for 2011 and 2012 was (1429 + 2085)/2 = 1757kWh. The immersion heater was switched off during this period.