Heating Audit

The heating audit makes practical observations for the heating system.

Current Performance of Heating System

The chart below shows a daily plot of gas consumption and degree days. (Degree days are a way of measuring the average temperature below the indoor temperature. The higher the value the colder the day).

Unfortunately the reading times of the two parameters are slightly out of synchronisation. The degree days are from midnight to midnight whereas the gas consumption is from 9:00am to 9:00am.

Certain periods may also be misrepresentative because the occupancy of the house varies causing higher consumption. This is likely to be a factor when the outside temperature becomes too cool to maintain a habitable inside temperature without heating.

Key Observations

  • Strong correlation between outside temperature and gas consumption
  • Severe influence of wind on gas consumption as shown by the peak at the beginning of the plot. This was a period of gales.

Visual Audit

At the start of the project a survey of the house was conducted and the following observations affecting the heating efficiency were found

Problem Impact Date Rectified Remedial Work

Radiator in small front bedroom is against the poorly insulated front wall and sandwiched between the bed. Increased heat loss and decreased heat output. 20/11/2012 Fit insulation behind the radiator. 
Radiator in large front bedroom is against the poorly insulated front wall. Increased heat loss. 20/11/2012 Fit insulation behind the radiator.
Radiators are placed under windows to counter act draughts from the cold window surface. This is less of a requirement if the house has double glazing.  This policy dictates that the radiator is on an outside wall which may not be necessary and is wasteful.

Also constrains the design of the room.
 TBC Move radiators to inside wall and/or more convenient position.
Curtain over radiator in the evening in small front bedroom. A large proportion of the radiators heat output will be behind the curtain. TBC Not an obvious solution without spoiling the look of the curtains.
Curtain over radiator in the evening in large front bedroom.  A large proportion of the radiators heat output will be behind the curtain.  TBC Not an obvious solution without spoiling the look of the curtains.
All radiators have thermostatic valves but there effectiveness is questionable given that there are often surrounded by other objects. Less than optimal heating control  TBC A more integrated system would be advantageous e.g. room thermostat that was better located and able to control the radiator valve. However, this solution would require appreciable investment.
The air vent in the dining room which is required for the gas fire and back boiler, creates significant draughts. The impact on comfort is considerable often requiring elevated temperatures to compensate. TBC A vital requirement especially with the rectification of other draught problems. The most obvious solution is to move the vent closer to the fire to reduce the impact of the cold air.
The Baxi Bermuda gas fire has a back boiler which is inefficient compared to modern condensing boilers. It also draws air from the room to operate and therefore an air vent is necessary. This introduces severe draughts effectively nullifying some of its heat output. Modern boilers have an air intake direct to the outside. Gas is burnt less efficiently than a modern boiler.  TBC Replace boiler.
There is a noticeable exchange of air between the upstairs and downstairs. This is felt as cold air in the form of draughts at the bottom of the stairs. The downstairs heating system is effectively heating upstairs and at the same time the draughts are causing discomfort.  TBC One possible solution is to fit door closers on the upstairs doors in order to reduce the air flow.
The outside vent does not have flaps that close the duct off from the outside. The kitchen quickly became cold and it became apparent on a cold windy day that an appreciable amount of air was entering via the hood.An electric heater had to be used to used when the main heating was off. TBCChange the outside vent to a self closing type.

Comparing Boiler Output to Outside Temperature

Why the comparison

It should be expected that boiler gas consumption varies with outside temperature. That is, the colder it is outside, the more gas is used. By quantifying this relationship it should then be possible to 
  • Determine the outside temperature at which the boiler can only just maintain a comfortable inside temperature.
  • Establish a datum from which to measure improvements.
  • Evaluate the accuracy of the calculations by comparison with the actual readings.

Work Carried Out

The gas meter is being read daily and the consumption plotted against degree days


A discernible correlation between consumption and temperature is observed although it also apparent that there are other factors that make this less accurate than ideal. For example
  • Heat loss due to the effect of the wind.
  • Heat gain from the sun.
  • Overriding the time clock
  • Changes to the main thermostat

Future Intentions

Automate the collection of data by using computerised data logging.

The Data


Chart 2