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rear of victorian house before renovationThe 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.

bay and sash window of old house before refurbishmentI’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.

savings from different types of window

Measures analysed:

The first five all relate to the single glazed bay sash windows and top light above the front door.

1a Secondary glaze and seal the 3 bay windows and front door top light (DIY)
1b Secondary glaze and seal the 3 bay windows and front door top light (Professional Measure)
1c Replace the 3 bay windows and front door top light with C rated windows (Professional Measure)
1d Replace the 3 bay windows and front door top light with B rated windows (Professional Measure)
1e Replace the 3 bay windows and front door top light with A rated windows (Professional Measure)

The next 3 relate to the 9 older double glazed windows
2a Replace the 9 other windows with C rated windows (Professional Measure)
2b Replace the 9 other windows with B rated windows (Professional Measure)
2c Replace the 9 other windows with A rated windows (Professional Measure)

The final bit of analysis was just used to determine the hypothetical cost for replace in the 9 windows with A rated window that would result in a 25 year payback
3 Replace the 9 other windows with A rated windows (25 year payback) (Professional Measure) 

The answer to the last one is actually £820 or £91 a window!