The house has a range of different types of window ranging from bay windows at the front, a single glazed top light above the front door, to 15 year old uPVC windows in most of the rest of the property.

For this exercise I've ignored three windows - the dining room window and side kitchen window as they will be altered as part of a potential extension, and the tiny toilet window as I haven't decided what to do with it yet.

When we model changes to windows as part of our Masterplan, changes to solar gains are included in the calculations as we take into account the amount of light that comes through different window types as well as their orientation and the geographical location of the house.

I've presented the results in a different format to highlight other useful ways of looking at savings other than just absolute financial or CO2 savings.

The peach rectangles represent the £ expenditure per annual £ saved by the measure - i.e. the smaller the better and also they are essentially equivalent to paybacks - £25/£ saved ~ 25 year payback.

The orange cylinders show the £ spend for each annual kg CO2 saved.  Again the smaller the better.  ~~Both of these represent cost effectiveness of measures either in saving money or reducing CO2 and are useful for setting thresholds. In the graphs I have set a £25/£ saved threshold as indicated by the red vertical line - only measures that don't exceed the line will be considered from an eco perspective.

It's Christmas so I thought I'd spoil myself and do some additional fun analysis on Air Source Heat Pumps and different Coefficients of Performance.  (N.B. as with other analysis this is only valid for the house I am looking to buy.) For those that don't know a Coefficient of Performance (COP) is the % heat energy that you get out of a heat pump compared to energy in.  An example is a COP of 200 means you get 200% energy out for energy in or twice as much energy out as energy in.  I know it sounds like some basic laws of physics are being broken but they aren't.  The energy in is actually 'work' and the energy out is the conversion of low grade heat (in the outside air) to high grade heat (inside).  The COP therefore doesn't take into account the amount of energy in the low grade heat as it is essentially free.

The graph above shows the results of my efforts.  The yellow line is the basic savings that can be expected compared to the current heating system in the house.  You can see that a COP of 225 is required for there to be benefit.  The blue line is the savings including a rough figure for the Renewable Heat Incentive payments - in this case a COP of around 120 is required.  For these calculations I've using a one tariff electricity rate. Anyone want to share their thoughts?

As I've explained, the house is going to need some major work not least the addition of a central heating system.  This is a large change and will have a significant effect on the whole energy use of the house.  This is important for how I decided to model the property....


The first thing we do to analyse a property, once the survey has been carried out and the model calibrated, is to apply individual measures to test their individual effects. In this case since one of the measures (a new central heating system) is going have such a large effect on most of the others, and also since the new central heating system is definitely going ahead, it would see sensible to apply it to the base case and evaluate all the other measures against the property with a new central heating system.


I can still work out the benefit of the central heating system by either carrying out that analysis first or by putting in an 'if I don't change the central heating system' measure.  This latter one will just give some negative savings (I hope!) equal to the positive savings I would have got by doing it the other way round.


We often do this when modelling changes that we know will effect many other things or are definitely going ahead.

I've modelled the house with its current fabric and heating systems.  As the appliances will be brought with us I've modelled our current lights and appliances and our expected use of them.  The model is therefore a bit of a hybrid of our expected used in its current building fabric.